# Cable Modem- Macs Slow, PC Fast



## zaxcom (May 7, 2006)

I have three Macs (G5,G4,G3) and one PC on my network. Until last week everything ran fine, then monday all three Macs started to crawl on downloads, but the PC is fine. Thinking my cable modem was bad I got a new one, no change, went back and picked up another cable modem, still no change. I took my router out of the system and hooked up my G5 straight to the modem and still my download speeds are in the crapper.

Every speed test I run the Macs top out at 1.2 Mb, while the PC gets 5Mb. My downloads are creeping. Time Warner came out checked all my lines and everything is perfect. My up and down SNR and levels are fantastic. I have very low ping and latency.  As I said the Macs have worked fast and perfect for 6 years until this past monday, and then all 3 at the same time hit the wall.

Time Warner brought a PC laptop over, hooked it to my network and it too got 5Mb down. They are washing their hands of the matter saying if the PC's work then its something wrong with the Macs.

I have turned off IPv6, tried forcing duplex and speeds, Cleared pref files, reloaded the entire OS. Even tried going all the way back to Panther, and still saw no improvement.

Equipment:
Surfboard 5101 Cable Modem
Dlink-604 Router (I can remove it, same problem)
G5 1.8Mhz single CPU
G4 800Mhz
iMac G3 500Mhz

All Run Tiger 10.4.6


Any help Ideas would really be appreciated.


Thanks


Zax


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## nixgeek (May 7, 2006)

Do you notice the slowdowns only when you're browsing the web, or is it also when you're downloading files?  Have you tried using other apps for web browsing and downloading in order to make sure it's not the applications that make it feel like it's downloading slowly?

Let us know what you find.


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## zaxcom (May 7, 2006)

Downloads have come to a crawl and so has web browsing. This is occuring in Camino, Safari, Transmit and my email program.


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## riccbhard (May 7, 2006)

Try this,

http://macosx.com/forums/showthread.php?t=271032


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## zaxcom (May 7, 2006)

Thanks, but I already went thru all possible combinations of duplex and speed. It had no effect on the problem.


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## zaxcom (May 8, 2006)

Problem solved. Went back to an old AMBIT modem and my speeds were back to normal. The new chip set for DOCSIS 2.0 in the Motorola 5101 and the new AMBIT modem is not compatible with Mac computers.


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## Doughboy (May 15, 2006)

I wouldn't really say that the problem is solved. I have no option to change modems.

This seems real strange to me... I think something that Apple should fix. It is definitely not a hardware issue - I heard that this slowdown problem also occurs on x86 hardware, but WinXP/Linux on exact same hardware performs fine.


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## MisterMe (May 15, 2006)

Doughboy said:
			
		

> .... I think something that Apple should fix. It is definitely not a hardware issue ....


Something that Apple should fix? Unless the OP is doing something really stupid like using a USB connection between his cable modem and computer, then there is nothing that Apple _can_ fix. A standard cable modem communicates via TCP/IP over Ethernet with the computer. I have never seen a Mac that demonstrated any trouble at all communicating via Ethernet.


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## Doughboy (May 16, 2006)

MisterMe... maybe it is not something Apple will fix, but it is definitely isolated to OS X. This problem we are all having occurs when upgraded to faster DOCSIS modems. I have Shaw Extreme which is 7Mbps down and 1Mbps up

We are all connecting via ethernet as far as I know. (At least I am).

I have 4 macs here that have slow downstream bandwidth (appears to be capped at around 2Mbps) with my new DOCSIS modem. On the same network I have a Linux and 2 Windows machines that do not have this problem and I get 5-7Mbps consistently on speed tests. At a completely different location (at work), I have same brand of modem and exact same problem when comparing Macs to other OS.

Now if zaxcom claims that by changing to an older modem causes speeds in OS X to go back to normal, then the evidence is pointing to an issue with OS X. It is not an issue which makes ethernet stop working, or causes any other ethernet issue on the LAN. It is isolated to internet traffic through the DOCSIS modem. Maybe something to do with how the packets are handled at a lower layer than TCP/IP. This is not a far-fetched possibility - For example, I have heard many problems with some brands of routers causing speed bottlenecks, or even instability and lost data with certain network and/or hardware configurations while other users have no problems at all. This issue we are having could be similar and is worth investigating by someone.


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## MisterMe (May 16, 2006)

*Doughboy*, I have no idea what problem you are having but I do have a DOCSIS cable modem. My Macs have no problems at all using the modem to access the Internet. I go through a Linksys wired router so that the modem doesn't actually see the computer. It sees only the router. Before I bought the router, I had to do power off the modem when switching between MacOS 9 and MacOS X 10, a known issue. This was a convenience issue, not a performance issue.

Your problem as described makes no sense. You ought to investigate your TCP/IP settings in the _Network_ preferences pane in *System Preferences*.


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## Doughboy (May 16, 2006)

MisterMe, It is not an issue of accessing the Internet. I can access the internet fine. The issue is a performance one - that with OS X the downstream speed is significantly slower than Windows XP or Linux. This is not noticeable in day to day browsing etc., nor are there any disconnection/connection issues. One has to do speed tests to see the problem. I have tried changing TCP/IP settings, swapped modems, adjusted parameters in the shell via sysctl with no luck.

Please try www.speakeasy.net/speedtest and tell me what your downstream is. I just tested and I got 1566 kbps down and 941 kbps up on my PowerMac and then tested right after with an XP Pro system and got 6804 kbps down and 917 kbps up.

Rather than rely solely on an Internet speedtest, I did a real world test also... downloaded same file off atitech.ca and watched the download speed in firefox - stabilized around 210KB/sec download with OS X and approx 2 minutes to download a 34.3 MB file. The same file downloaded with XP and firefox took only around 30 seconds and stabilized around 850KB/sec. To rule out possibility of OS X build of firefox having poor performance, I tried the same download in Safari and got the same slower speed of around 220KB/sec.

And I am not the only one with the problem... xaxcom posted that he was able to try an older modem and the performance went back up. In my previous post I was pointing out that it is possible for hardware to cause performance issues even though it appears to work fine. There appears to be something in the way OS X's ethernet communicates with the DOCSIS modem which causes it to operate slower than expected.


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## MisterMe (May 17, 2006)

*Doughboy*, I did the test as you suggested. You may find the results difficult to accept, but they may explain the performance disparity between your Mac and Windows computer.

Using *Safari 2.0.3 (417.9.3)*, my results are 5045 kbps download and 590 kbps upload. My connection is rated at 5 Mbps. This is inline with the other connection speeds I measure on the DSLReports.com  website. Within expected variation, I am getting the performance I pay for.

In a moment of inspiration, I conducted the speed test again on the same hardware. This time I used *Netscape 8.1* running on a fully updated Windows XP SP2 on *Virtual PC 7.0.2*. The results are 7049 kbps download and 1017 upload. This result is clearly not possible. The Windows browser claims that my connection is 40% faster than the line I pay for. Windows running under emulation on MacOS X cannot be faster the host MacOS X alone. It certainly can't overclock my ISP connection.

What is clearly going on here is a bug (or feature?) in the Windows port of Java. Accept your lower MacOS X numbers in the knowledge that they are accurate.


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## Doughboy (May 17, 2006)

Your test seems fine under OS X. The VirtualPC test does not explain my problem because I am using a real PC to compare. (FYI, I also ran the speedtests in VirtualPC on my Mac and got slower than expected results - less than 2mbps).

I initially thought it was due to Flash being slow on OSX (speakeasy uses Flash program), causing the results to be lower than expected. That does not explain the slow download test - over 2 minutes on my OS X compared to 30 seconds on XP. I am going to see if I can test an older Teryon modem (which is not DOCSIS) and see if the downstream is approaching the 5Mbps that is advertised.

MisterMe, can you tell me what make/model your modem is?

Mine is a Motorola SB5101 Surfboard Modem.


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## MisterMe (May 17, 2006)

Doughboy said:
			
		

> Your test seems fine under OS X. The VirtualPC test does not explain my problem because I am using a real PC to compare. ...


You don't understand. *Virtual PC* emulates a slow PC. The results of Windows running on the emulated slow PC are higher than those on native MacOS X. Since the two tests were run on the same hardware, the only difference between the two test was software. I could have run the Windows test using *FireFox* or *Internet Explorer*, but that would have been expected to "speed up" Windows even more. The point is that the numbers generated by the Windows test are unbelievably high. The numbers generated by the MacOS X test are as advertised.



			
				Doughboy said:
			
		

> .... I am going to see if I can test an older Teryon modem (which is not DOCSIS) and see if the downstream is approaching the 5Mbps that is advertised.


Is your ISP still compatible with your old briefcase-sized Teryon cable modem?



			
				Doughboy said:
			
		

> MisterMe, can you tell me what make/model your modem is?
> 
> Mine is a Motorola SB5101 Surfboard Modem.


I have a Toshiba PCX1100U.


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## Doughboy (May 17, 2006)

MisterMe, I tried VirtualPC again and I am getting those real goofy high transfer speeds. I then tried to download a large file using Internet Explorer within an XP session in VirtualPC and I timed it with an external clock - a 40.9 MB file took 2 minutes and 15 seconds even though the transfer rate said 780K/sec. I downloaded the same file on a real PC running XP using Internet Explorer and the transfer rate said about 820K/sec. but it downloaded the file in 55 seconds. VirtualPC is not to be trusted with doing any sort of Internet speed tests.

MisterMe, sounds like you disbelieve me (I am not the only one with this problem btw) and I don't really blame you because it is difficult to believe unless experienced for yourself. I was hoping that someone knew more info about this problem and have some magic internet setting/tweak that I could do to solve. I have tried them all... change MTU, turn off IPv6, manually configure ethernet adapter to full duplex etc. I have tried with a router, and also my Mac directly into the modem. I have tried several different Internet speedup/optimizers for OS X and even an official one from Apple designed for FOS. Nothing I have tried caused the speed to increase.

To summarize...

I have a DOCSIS Motorola modem. Shaw Extreme 7Mbps down 1Mbps up.

Typical tests at speakeasy.net/speedtest : XP Pro 6883 Kbps down, 903Kbps up. Mac OS X: 1563Kbps down, 940Kbps up. (note these tests vary slightly every time)

Downloading large 32MB driver file from know fast site (atitech.ca): XP Pro 30 sec. at around 850 KB/sec and Mac OS X over 2 minutes at around 200 KB/sec.

As a control, I put that same file on my local linux server and downloaded in firefox on OS X. It dowloaded so quick that it was difficult to time. I then used a much larger 1.4GB test file which took under 2 minutes at around 11000 KB/sec.

I can transfer on LAN at high speeds to/from XP/Linux and OS X. This speed issue only affects packets via the Motorola modem. Others have reported same problem only when they upgraded their cable service to a higher speed and changed the modem. The older modems seemed to work fine, and one person in this thread "solved" by replacing modem and speed went back up.

The problem could be Apple or Motorola. Since the Motorola modem works fine with XP and Linux, therefore it is leaning towards the problem being solvable on the OS X end. Maybe there is some sort of QOS thing going on that the Motorola is signaling OS X into doing.

My network still works with the Teryon modems.


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## MisterMe (May 18, 2006)

*Doughboy*, if you are getting 11,000 kbps when when your Mac transfers files from your Linux server, then there is nothing wrong with your Mac's Ethernet performance. You seem to have an issue with DOCSIS modems with your ISP. The fact that you and other people experience the same problem is not evidence of a general problem with DOCSIS modems. Many other people, including I, have DOCSIS modems which work fine with our Macs.

The fact that your Teryon modem seems to work better than your Motorola modem with your Mac leads me to believe that any real problem must lie with the Motorola. I take it that you own your own modems. You should seriously consider replacing the Motorola with a new DOCSIS modem. As you know, you have to register the serial number and MAC address of the new modem with your cable ISP.


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## kvillines (Jun 26, 2006)

Well DoughBoy, I am having the very same problem you are and I have the very same setup you do. I was just setup with a new SB5101 to replace the old SB4220 and my performance fell through the floor. The PCs on my LAN are all fine with download speeds over 9000 kbps while the macs (one intel and the other G5) both are hovering around 793kbps down.

I tried going back to the SB4220 but it wouldn't sync up. The Cox Cable has been NO help at all. Any suggestions from anyone?


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## Whiteshark29 (Jun 29, 2006)

Try this to speed up your connection
http://www.apple.com/support/downloads/broadbandtuner10.html


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## redraider (Jul 6, 2006)

I have to agree with Dougboy. I started a thread regarding the same issue.
http://www.macosx.com/forums/showthread.php?t=272957
I "think" there is a valid issue out there and it should be acknowledged by apple even if thier answer is, we know there is a problem and don't have a solution. That would at least keep some of us from spinning our wheels all day long trying to solve it on our own.


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## ishwara (Jul 12, 2006)

I had Comcast come by to do a routine check of my Internet speed today. they sent him out for free, as I was threatening to change to DSL.

He brought his PC laptop and measured speeds around 4 MB/sec - which is the level of service I am paying for. He used speakeasy.com for his tests and also dslreports. All yielded the same results.

He measured at the modem and in two remote rooms. I have a CAT6 LAN system - not wireless. Results were the same everywhere.

However, both my G3 and my G4 clocked dowloads at about 380 kbs. I have tested Safari, Firebox, 10, 100, half duplex and full duplex. There are slight and inconsistent differences. I did not run enough tests to have a legimate sample to average. However the differences - if any - are not worth worrying about.

According to my database, I have a Motorola SB4100 Cable Surfboard modem. I have had it for several years.

I am running Mac OS 10.4.7

I was shocked to learn how fast I could be downloading if I had a PC. I doubt I have ever had download speeds approaching half a MB - much less 4 mb. I am sure I would have noticed.

We had a very strange observation. On the G3 only, uploading was in excess of 7 MB/ second. We ran this test several times. It actually appeared that the test had not run at all, since the speed was blazingly fast. But each time it posted a speed at the bottom of the page.


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## ishwara (Jul 12, 2006)

I did not notice any effect after installing Broadband Tuner 1.0


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## Satcomer (Jul 12, 2006)

I had the same experience with Motorola cable modems in the past. For over a year I changed put cables, routers and such with no change. I then decided on a word from a friend to use ANOTHER brand of cable modem. Strangely my cheap D-Link Cable modem macs my Macs go back to regular speed just like my Frankin PC running XP. Before changing I contacted my ISP to verify they support the modem I bought. After this experience I urge anyone within my ear shot of my voice to stay away from Motorola cable modems.


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## redraider (Jul 12, 2006)

well I have a RCA digital broadband modem, model dcm425 and am experiencing the same issues people with motorola modems are experiencing.


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## bobw (Jul 12, 2006)

Could be a router problem. I've seen this with Comcast.

I have Comcast with a Motorola SB 4220 and a Netgear wireless 814 router. Both my Macs, one wireless and my PC get the 4MB speed. No difference for either Mac or PC for me.


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## redraider (Jul 12, 2006)

On the tests I ran I took my wireless router out of the picture. my router is not the issue. You can see all the tests I ran at the link
http://www.macosx.com/forums/showthread.php?t=272957


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## sunyata (Jul 18, 2006)

I just switched from DSL to cable using Comcast and am experiencing the same thing. On my PC I am getting between 8 - 10M, and on all the Macs, its between 800K and 1.3M.

Quite frustrating. I'm about to go buy a new modem, but am worried it wont do the trick.

What is the status of this issue?


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## ninepoundjammer (Jul 24, 2006)

This is indeed a problem with certain modems, hard as it is to believe.  I even spent about an hour on the phone with apple support trying to get them to take it seriously.  While they admitted there was likely an issue, their position was that it was the modem manufacturer's problem.  Even if it is, I'd like them to show some sort of concern, which they didn't.

I've had tried three modems, a linksys?, Motorola SB5120, and Motorola SB5101.  SB5120 makes Linux, WinXP and Mac perform similar.  The other two modems squash the Mac performance while leaving Linux/WinXP unaffected.  Unfortunately the SB5120 doesn't play nice with Comcast and goes down a few times a week.

Suggestion, keep trying modems till one works properly.  Call apple and ask why they don't care about you.


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## TimF (Jul 25, 2006)

You bet I'm calling Apple. This problem just happened to me today. The 3 year-old Terradyne (sp?) rented modem from Comcast started getting flaky with dropped packets, etc. The Comcast tech said it was old and I should swap it out for a new Motorola SB5101.

I was getting 2-4 Megs (on an 8 Meg connection) with the flaky modem, but it was periodically choking and dying, performance-wise. So I was excited to be able to get some blazing speed from a new modem. NOT!

The Speakeasy test, among others, was showing me throttled back to 2 megs or less, just as described here. I called Comcast support and they showed the modem working flawlessly. My Mac was directly connected, but same results through my Linksys WiFi. My Mac is a MacBook Pro 17", 2GB RAM, 100GB 7200rpm HD. The very best laptop that Apple has to offer today.

So I ran to get my ancient Compag Armada, plugged it into the modem and lo and behold, 4-5 megs average easy. WTF! I say, and on a whim I launch Parallels Desktop for Mac on my MBP. Parallels has Win XP Pro, SP 2. The speed tests were averaging 6-8 megs (and better) to servers all across the country.

Now even if these online speed tests are not that accurate, you gotta see that something is very wrong with Mac OS X, especially Tiger, with this Motorola modem. And other modems, apparently. This really sucks if Apple won't acknowledge the problem.

Where can I find a list of Comcast compatible modems? I certainly won't put up with this.


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## ninepoundjammer (Jul 25, 2006)

So, I've been working this issue for about 7 months now, and may have made a breakthrough today.  Since my Motorola SB5120 has connection problems I called motorola to see about either a firmware upgrade or warranty on it, since I purchased it 7 months ago.  They said that the "T3 time-out" error I was getting on the modem logs indicated a problem with dropped packets on the comcast head-end (CMTS).  The working hypothesis is that packets off my PowerMac are for some reason dropped more frequently than those off my WinXP or Linux boxes.

Great to see that the first two comcast techs that came out had no clue what this error meant.  I'll need to get another clueless comcast guy out and beat that one into sending out a real line tech.

Should have occured to me long ago that my modem connection issues might be related.  Just strange that only the OS X machine is affected.  May not be Apple's fault after all.  Almost makes me feel bad about the hard time I gave the "Genius" at the Genius Bar this morning... nahhh... if those guys are geniuses...

Keeping my fingers crossed...


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## ditti (Jul 27, 2006)

In researching a solution to my slow speed problem, I landed here. When talking to Charter cable service customer rep earlier today about upgrading to 10 mbps... I mentioned that I never noticed any big difference in speed when I upgraded  from 3 mbps to 5 mbps several months ago. She told me how to run my first speed test today, and when I gave her the results... she  said she's sending tech tomorrow morning to check the lines. Tonight I thought I'd test my two PC's and found they're running almost 4 times faster than my Mac G4... so the search began to find out why. Just so you guys know... I'm running Mac OS 9.2 and using Motorola SB5100 Surfboard Modem. The problem doesn't seem limited to Mac OSX. Think I'll try that cheap D-Link modem I read in earlier post if Charter says its compatible.


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## luservegas (Jul 28, 2006)

I am also having the same problem. I previously had a Motorola SB5100, and I was getting max speed on my Comcast 8/768 connection. I just recently moved and the tech installed a SB5101 Modem. Speeds dropped through the floor to about 1600kbps. On my PC, I am getting about 8000kbps. I tried dealing with Comcast tech support, but that's really a lost cause. I went out and bought the newest Linksys Modem, a BEFCMU10 ver.4 and had the exact same problem. I did some research on different speed tests and found one that tested on port 8500. The speed was almost 8000kbps and QOS was around 90%. On the tests which utilized the http ports, speed was about 1600kbps and QOS was somewhere around 60%. I decided to try downloading a live version of Ubuntu to rule out the mac hardware as being a problem. I started doing a download via my browser, averaged about 300kB/s. I restarted the computer (I had the idea to try a PCI Ethernet card, so I shutdown before the DL finished. Needless to say the PCI Ethernet card did not work.) I went back to the Ubuntu site and this time I downloaded a torrent - when I started DL the same distro via bittorrent, the speed went back to about 8000kbps. It's a bit of comparing apples and oranges, but I got to thinking and it seemed like all of these speed problems occured when http ports were being used. I did some more research and stumbled upon something about name servers causing some latency. I decided to try using public name servers instead of Comcast's DNS servers provided with DHCP. The speeds in the Speakeasy test are now in line with the tests that I get on the PC, right at my max provisioned speed.

If someone else with this problem can try this out and see if it helps with their speed issues, I'd love to hear the results.

I just added the following DNS Servers in the field in SysPrefs/Network - Built In Ethernet, TCP IP. Field is DNS Servers (optional).

4.2.2.1
4.2.2.2


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## captaincanuck (Jul 30, 2006)

Hi guys,

I too have the same problem with slow download speeds, I currently have an SB5100 modem from Shaw Cable up here in Canada.  I switched over to cable from dsl and have 7Mbps down/1Mpbs up.

Everything is fine on my winxp computers on my network, I recently bought an intel imac and now have a macbook as well.  Both suffer from the slow download speeds.  I can get the advertised speeds on my windows pc's but not on my macs.  

what's interesting is running xp on parallels on my mac yields fast speeds downloading thru apple's website and running speakeasy's speedtest.  OS X seems to be capped b/w 2-3Mbps for download and upload speeds aren't affected.  So its not the actual hardware because xp thru parallels is fine, so it has to be OSX that is doing something...

Another interesting thing I found is that if I run a multipart download on OS X the speeds are fine.  Using the 'downloadthemall' extension on firefox, I can get the 7Mbps speeds in OSX if I run a multipart download, so it seems something is happening in OSX that stops it from downloading at full speed with a single download thread.


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## luservegas (Jul 31, 2006)

Changing DNS Servers is only a temporary solution - speeds revert back to the slower speed after a couple of hours. I just went out and bought a D-Link Modem and everything is back to normal. Not sure if the Linksys uses the same chipset as the SB5101 (Broadcom BCM3349.) I emailed Linksys support about this problem, and they're assertion was that something was wrong with my Macs. I still haven't heard back from them after explaining the situation again.

Bottom line, stay away from the Linksys and the Motorola SB5101. The SB5120 supposedly works fine, but it seems like people haven't had good luck with it syncing with comcast. D-Link DCM-202 works like a million bucks.

There are several other threads on other forums: dslreports.com and macfixit.com - do a search for sb5101 macintosh.


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## ditti (Aug 1, 2006)

Thanks luservegas... I look forward to trying the D-link!

P.S. When the Charter techician showed up... I knew I was in trouble when I showed him my printed Speed Test Result page just like Charter's customer service rep told me to and he asked where I got it. I told him that Charter's customer service rep told me to go to the Charter site and run the test. Charter's technician didn't know they had that capability! Guess we both don't know much. He then asked me to go to Charter's site to show him where I ran the test! Said he learned something new. Anyway, he called one of Charter's two technicians who know a little something about Macs and he didn't know why my Mac was running slower than my PC. Also interesting... he said that the tech guys find that Motorola modems work best with Charter, but then again, they don't see many Mac users!


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## bobw (Aug 8, 2006)

From MacFixIt;

Motorola cable modems operating more slowly with some Macs than with PCs
There appears to be an issue affecting some Motorola SurfBoard cable modems that results in lower throughput speeds when the devices are connected to Macs than when the devices are connected to Windows-based PCs.

Several posters to an Apple Discussions thread note that Motorola Surfboard 4200, 5100 and possibly other models deliver significantly lower throughput on Macs when compared to PCs -- generally with Macs achieving about one-third of the bandwidth available to PCs.

Poster salientis has received an official response from Motorola regarding the issue, acknowledging its existence:

"Engineering is still investigating, but has identified a possible issue between Apple computers and certain networking configurations. Due to the fact that multiple devices are involved, the root cause is not yet known. We are continuing to investigate and will take the appropriate action once the cause and correction are known."

So far, the best workaround for this issue appears to be use of a modem from another manufacturer, or an older Motorola modem (outside the 4000 and 5000 series')


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## ]Michael[ (Aug 14, 2006)

I use to have a Moto SB from Comcast and I got sick of losing the connection.  I disconnected it and hooked up my Terayon that I got for free from Cox cable when I lived in Las Vegas.  It worked great all year.  Never lost the connection once.  About a week ago my connection went from the average of 800 KBs (up to 2 MBS) to an average of 56 KBs.  No idea why but, I'm getting quite frustrated. What use to download in minutes now takes hours.  I have tried tweaking and I checked all the connections.  There is no reason for it. And I'm out of ideas of what to do.


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## ]Michael[ (Aug 14, 2006)

I guess the results I got from one site explained it.

_
Checking for Middleboxes . . . . . . . . . . . . . . . . . .  Done
running 10s outbound test (client to server) . . . . . 3.54Mb/s
running 10s inbound test (server to client) . . . . . . 5.64Mb/s
Your Workstation is connected to a Cable/DSL modem
Information: Other network traffic is congesting the link_

Typical Comcast/Monopoly.  Bill everyone more and more and the let the infrastructure be over taxed and useless.


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## gsahli (Aug 16, 2006)

Also from Macfixit (and versiontracker):
http://www.versiontracker.com/dyn/moreinfo/macosx/14943

"What's new in this version:

    * Add "Motorola SURFboard" preset that sets net.inet.tcp.delayed_ack=0 for use with DOCSIS capable modems. "


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## Doughboy (Aug 18, 2006)

gsahli said:


> Also from Macfixit (and versiontracker):
> http://www.versiontracker.com/dyn/moreinfo/macosx/14943
> 
> "What's new in this version:
> ...



So could one just do this ? ...

sudo sysctl -w net.inet.tcp.delayed_ack=0

I am going to try at lunch, will report back!


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## nels0360 (Aug 18, 2006)

Something very strange is going on here.

I have a Linksys Cable modem v4.  I have tried two different ones and they behave the same.  With the Linksys modems, any speed test I run comes in at 1000-1500 kbps on a Mac.  But if I download acrobat reader from adobe (very fast), it will come in around 1MB/s which is where my Comcast should be.

If I switch to a Motorola Surfboard 5120, all the speed test register properly and all download are fast.  Any ideas?


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## Doughboy (Aug 19, 2006)

I tried that delayed ack to 0 and it didn't make any difference!


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## kwojcik (Aug 20, 2006)

After reading all the postings on all the different sites (and there are ALOT) about the Macs being slow and PC fast, I have noticed that there are differences and similarities.
1. I noticed that it is NOT a modem manufaturer specific issue.
2. I noticed it is NOT provider specific, but it seems to be regional within the provider.
3. There have been reports of success with certain modems from RCA and Motorola, and some others.

The reason I looked all over for this research was the fact the my brother had contacted me with this same issue. He is on a Comcast connection in SE Pennsylvania and was running a Linksys "All-in One" WCG200 modem/wireless router. He did all the tests (Mac vs. PC) and tried all the fixes suggested to no avail. Referring back to my observations earlier, I found that there was only 1 common factor with all the modems that "fixed" the speed issue. That is All the modem that works had TurboDox in them. I had him go out an buy a Motorola SB5120 modem (TurboDox enable) modem and have it provisioned by Comcast. His speed went from and average speed of 1Mbps to 12Mbps directly connected to it.
So my logical conclusion would be that the Cable Providers are doing something with TurboDox and for some reason the Macs don't play nice if a TurboDox modem is not in line. I live in Central Delaware and I have a Motorola 4100 series (I believe) and a Netgear FWG114P router and get 8Mbps. At a site in Northern Delaware (on a different system) My PowerBook speedtests at 1.5Mbps while the PCs get 8-12Mbps. This is where the Regional observation comes into play as this site was also Comcast.

So, If your are have the slow speed issues, It may be worth trying a TurboDox capable modem. Either buy one or try to get the Cable Company to replace yours with a newer model that has TurboDox.

Good Luck to anyone that has the speed issues and I hope that my experiences help someone (even if it helps one person reading this, It was worth all the effort).


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## redraider (Aug 21, 2006)

Just a FYI for anybody that might have been reading this thread. I kept doing
more reading and I read about the dlink dcm-202 cable modem, you can buy it at best buy. It's got turbodox on it. I upgraded the firmware on the modem (requirement for comcast users) then I plugged it in, called comcast. I had them register the mac of the modem, it took them 15 minutes to get the modem registered and connected, got on the internet. Gees what a difference this modem makes. I went from a average download speed of 256kb/sec to 850kb/sec on my imac. My pc and mac peaked at 1.2mb/sec when downloading files. I haven't run a speed test yet on dslreports but I will soon.


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## Doughboy (Sep 29, 2006)

Hooray! OSX update 10.4.8 fixed this problem!

Here is my speedtest on speakeasy just after the update using Firefox...

Download Speed: 9538 kbps (1192.3 KB/sec transfer rate)
Upload Speed: 939 kbps (117.4 KB/sec transfer rate)

I also got similar results with Safari!


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## ]Michael[ (Sep 29, 2006)

Doughboy said:


> Hooray! OSX update 10.4.8 fixed this problem!
> 
> Here is my speedtest on speakeasy just after the update using Firefox...
> 
> ...



Same here.
Download Speed: 12419 kbps (1552.4 KB/sec transfer rate)
Upload Speed: 356 kbps (44.5 KB/sec transfer rate)

I'm going to be very afraid to run the next update for fear it will revert to the 50-150 KB/s I was getting for the last 5 months.


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## zaxcom (Sep 30, 2006)

Are these new speeds being seen only Comcast or on other systems now that Apple made the fix. I am hestitant to go over to Time Warners office and get one of the newer modems for fear it may still not work, and I may not be able to get my old modem back again.


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## simbalala (Sep 30, 2006)

zaxcom said:


> Are these new speeds being seen only Comcast or on other systems now that Apple made the fix. I am hestitant to go over to Time Warners office and get one of the newer modems for fear it may still not work, and I may not be able to get my old modem back again.


Go get one and hang on to your old one till you're happy.

With the volume they purchase modems at one month's subscription probably pays for the thing. They don't really care.


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## Doughboy (Sep 30, 2006)

zaxcom said:


> Are these new speeds being seen only Comcast or on other systems now that Apple made the fix. I am hestitant to go over to Time Warners office and get one of the newer modems for fear it may still not work, and I may not be able to get my old modem back again.



I am on Shaw Cable in Western Canada, therefore it fixes other systems too. I wish Apple would have made it clearer in the release... like say something such as a fix for performance issues on some DOCSIS modems.

I have a Motorola DOCSIS modem and Shaw Extreme (10Mbps/1Mbps)


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## zaxcom (Sep 30, 2006)

Well its almost a full fix, but not really.  I went down to Time Warner and picked up a brand new modem. Its an Ambit, much smaller than my 4 year old Ambit. This new Ambit uses the same Broadcom chip set as the Motorola. Brought it home and ran several speed tests on several sites.

With my old Ambit I can max out at my cap which is 5mb. Testmy.net and the local RR test all hit me at 4.99mb.

I put the new modem on next.  In the past the best I could do with this modem before the Apple fix was 3mb. Now with the fix it maxed out at 4.5mb.  While this is a huge improvement over the old speed, it still falls short of my old modem.  I ran the tests many times to make sure it was not a momentary thing.

I put the old modem back on and was right back at full speed.  So I am going to stick with the old modem.

While Apple has solved most of the problem Motorola and Broadcom have both admitted on other sites (and in an internal memo to Time Warner I had privy to) that there is a bug in the design of the chip that only affects Apple computers. Motorola says they are working on a fix. Motorola did suggest turning off Delayed ACKS as one fix, but that did not fully solve the issue either.


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## Doughboy (Oct 2, 2006)

zaxcom, were you able to speed test both modems under a different OS (windows or linux for example) to rule out a flaw in the new Ambit modem.


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## zaxcom (Oct 2, 2006)

The windows machine was fine, Only the Macs showed the difference.


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## bobw (Oct 2, 2006)

Comcast

MacMini 1.4.2 PPC  OS X 10.4.7   - 2754 kbps 
G4/2GHZ - OS 10.4.8 - 5150 kbps


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## ]Michael[ (Oct 2, 2006)

Never mind


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## zaxcom (Oct 3, 2006)

I am taking a chance. I saw that NewEgg has the Moto 5120 on sale for $49. Wanting to use a more modern and DOCSIS 2.0 modem, I ordered one. It should get to me tomorrow and I will post my results. If it does not work I have a month to send it back to NewEgg.


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## zaxcom (Oct 5, 2006)

Got the 5120 today, hooked it up and was running at full speed. I am reaching my upload and download caps. I think this shows that the Broadcom based modems do not work well with Macs, but the TI based ones do.  I am a happy puppy.


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## bamamatt (Oct 26, 2006)

I'm having a similar problem...Slow web page loading, however, I get fine speed tests. 

The issue is just a terribly long delay on OS X before the page begins to apprear in the browser, and then when it finally begins, it seems to come in bursts, and takes forever to finish the whole page.

I have the Motorola SB4100 running on Charter cable.  My XP machine works fine.  All upload/download tests are fine on both XP and OS X.  It's just the slow web page loading (long delay before start). I even downloaded the latest FireFox, to test it, but no help.

I'm running OS X 10.4.8 (the ltest update did not fix my problem, as reported by others with the slow upload/download spped problem).

This is a strecth, but it worked: I loaded WinGate Server on the XP machine, and assigned the HTTP proxy on the Mac to point to the XP/Wingate Server, and boom! web surfing is now fine.  But, I do not want to keep my home network set up that way.

A Linksys router sits between the machines and the cable modem. The performance is the same on OS X even if I remove the router and go direct to the modem.

It sure seems like that stupid Motorola modem. Some say 10.4.8 fixed the problem of upload/download overall speed, but I don't know about this slow web browser surfing problem. It hasn't fixed it for me.  The XP box is always fast, but the Intel iMac is usually slow.

Some people named this DOCSIS thing in the Motorola SB 4100 as the culprit and say that a D-Link DCM-202 modem will fix the problem, but it seems to be DOCSIS also, so I do not know if I should buy one just to find out. Plus, how can I know is that modem will work on Charter cable. Is there a chance it will not?

Any advice will be greatly appreciated.


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## KenDRhyD (Oct 27, 2006)

One thing that can be considered is the placement of a router, even a wireless router, between the computers and the cable modem. Since all immediate communication would be between the computer and the router, the actual cable modem should not enter into the issue (other than the router-cable communication issue, which has not semed to be much of an issue for me to date).

I have used cable modems in the past, and the use of the router not only permitted multiple computers to seamlessly share the internet connection, it significantly reduced the connectivitiy issues. These days I am using DSL from a Canadian phone service supplier, but the wireless router still isolates the computers from the specifics of the DSL account, and I am running at full speed (subject to network traffic).


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## bamamatt (Oct 27, 2006)

I *DO* have a router between the two machines (1 XP and 1 iMac) and the modem.

Problem on the Mac machine still happens as stated earlier.


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## zaxcom (Oct 27, 2006)

As I stated before, the only cure seems to be getting a modem that does not use the Broadcom chipset. The Motorola 5120 uses a TI set, and it works perfectly with my Macs.


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