Cable Modem- Macs Slow, PC Fast

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.
 
well I have a RCA digital broadband modem, model dcm425 and am experiencing the same issues people with motorola modems are experiencing.
 
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.
 
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?
 
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.
 
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.
 
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...
 
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.
 
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
 
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.
 
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.
 
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!
 
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')
 
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.
 
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.
 
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?
 
You must log in or register to reply here.
Back
Top