# > Overclocking G4 867mhz...



## tumbleguts (Jun 12, 2005)

Having done the research and found (too) many sites on how to overclock the G4 867mhz processor in my Quicksilver - I've decided the time has come to go ahead. However one question remains...933mhz or 1ghz.

I orignally planned to overclock to 933mhz (one jump). My reasons: 
> the 7450 cpu already runs quite warm - one jump is probably enough.
(Although a different cooling fan could fix this...)
> the L3 cache SDRAM is rated for 250mhz.
867mhz = L3 217mhz. 
933mhz = L3 233mhz
1ghz     = L3 250mhz.
From what I've read it seems that in many cases the L3 cache became disabled when this processor was overclocked to 1ghz. That is why I was only planning to go to 933mhz. But if 1ghz is possible I would certainly like to try. Can I downclock the L3 cache?

Does anybody have any information or experience with this?


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## Zammy-Sam (Jun 13, 2005)

I have only one spoiling comment on this:
If the G4 867mhz is too slow for you, do you really think 933mhz or even 1ghz will be different? And is that worth to damage the system and completely lose it? Why not add more ram (if possible) or just save for a new system?


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## chornbe (Jun 13, 2005)

'zactly. Simply not worth the real and considerable risks, IMHO.


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## tumbleguts (Jun 13, 2005)

> eh, that is slightly a "spoiling" comment...

Although, thank-u for your concern. I can understand if overclocking is not a familiar thing, it could be seen as more trouble than it is worth. Generally I have found Mac users not to be too accepting of hardware modifications such as overclocking the processor. However, let me assure you that I have covered the risks and have quite a bit of experience. I have overclocked every Mac I've owned starting with my beige G3 333mhz (to 366), then a G4 466mhz (to 533), and a G4 733mhz (to 867)  - and every one of those overclocks have been both wildly successful and very, very stable. Apple is traditionally very conservative in setting their processors and usually for good reasons. They have a reputation to uphold, and their products are considered reliable workhorses. As a consequence, they set their processors slightly below the achieveable speeds.  So, I have found that with adeqate cooling most processors are able to make two jumps (clock-ups) in speed very easily.

It's not so much that the current G4 867mhz is too slow - it's more about maximising what I have. 933mhz isn't really much much difference - but it does provide nearly 9% performance increase. Sure, that's not a lot - but like I said; if I know it can safely do that speed (with proper cooling) well, I want to take advantage of it. As for RAM, I already have 1.5GB CL2 SDRAM installed (can't take anymore). And that raises another point. Using CL2 RAM over CL3 RAM gives approx. 5-8% increase in RAM performance. Just as I was prepared to spend a little more money obtaining CL2 RAM, I am prepared to take a "well considered" risk on getting the most out of my current processor. The "real and considerable" risks may exist for those who have never attempted the fine soldering required to perform this mod, but for me who has both experience and confidence - it's no risk at all. Once I overclock I throughly test the cpu for ANY signs of unstability and provide the adequate cooling that is needed to prevent any damage. I do an enormous amount of research before I attempt any hardware mod - and risks would definately exist for those who do not know what they are doing. Yes, I could save up for a better processor (and to be honest, I'm already doing so), but until that happens I'm the kind of guy that likes to tinker... 

Which brings me back to my original question. I am planning to overclock my G4 867mhz processor (more for my own satisfaction rather than a huge increase in performance). From my research it seems that 933mhz is very achieveable but there have been conflicting reports of 7450 cpu's overclocked to 1ghz. This is manly due to the fact that the L3 cache is maxed out at that speed. 

If anyone has any information or experience in overclocking a G4 867mhz to 1 ghz, please let me know. Lets not turn this thread into a "should or shouldn't" - because I'm going to do it regardless! But, (as a part of my research) if others have some practical experience and knowledge with this before I go ahead - I would love to hear from you. If anyone else wishes to obtain information on overclocking their Mac processor, I would be happy to help.


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## Zammy-Sam (Jun 13, 2005)

tumbleguts said:
			
		

> I am planning to overclock my G4 867mhz processor (more for my own satisfaction rather than a huge increase in performance).


If only you started your thread like this... I would have spared you with my unusable comment.


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## TommyWillB (Jun 13, 2005)

Zammy-Sam said:
			
		

> I have only one spoiling comment on this:
> If the G4 867mhz is too slow for you, do you really think 933mhz or even 1ghz will be different? And is that worth to damage the system and completely lose it? Why not add more ram (if possible) or just save for a new system?


I have a QuickSilver G4 with 1GB of RAM.

I recetly bought an iBook G4 1Ghz with only 256 MD of RAM. I was completely surprised when the little iBook outperformed my QuickSilver.

However, creating a new user account on my QuickSilver performed faster. So I think the fact that my QuickSilver has been upgraded so many times, and has a huge pile of user modifications and preference is slowing it down.

I've been seriously thinking of doing a clean rebuild of my machine's OS, etc on it's 2nd internal drive. I'm not sure how that'd compare to overclocking, but but seems a lot safer.

The undercurrent that nobody seems to talk about is that with OS X we seemed to have inherited that very annoying WinDoze-like issue of the machine getting slower over time. That's why WinDoze folks are always wiping and rebuilding thier machines. I'm quite dissapointed that we now need to do the same thing with our Mac's.


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## tumbleguts (Jun 14, 2005)

Granted, the processor is only one hardware part of many that enables a Mac to perform faster. Other system bottlenecks include; hard drive (one that many overlook), memory, and graphics card. Then there is the speed of add-on hardware such as the CD-RW or DVD drive and speed of connection ports. Even after all that, you can have the fastest hardware, but if your software is not configured well - performance will elude you. Lets go through this one by one.

Hard drive. Many have stuck with their stock (and usually noisy) 5400rpm drive and wonder why their computer is so slow. A faster 7200rpm drive certainly does wonders. Keep in mind that the ATA interface on Quicksilver's is ATA/66 - roughly meaning 66MB/sec. Given that most 7200rpm drives max out between 35-45MB/sec sustained transfer rate - the ATA/66 is fast enough. You may have an ATA/100 (or above) drive, but connecting it to a PCI ATA/133 card isn't going to make that drive transfer faster. If you want better hard drive IO performance you are going to have to go ATA serial or SCSI. I personally got a Adaptec 39160 64 bit SCSI card and connected up two 10Krpm (quiet and cool) SCSI drives. I'm happy to report that I'm getting a transfer rate of between 115-130MB/sec from a boot-able RAID - nice.  

Memory (RAM). Depending on how you use your computer, more memory can certainly speed things up. 512MB is considered the absolute minimum for running Mac OS X - sure, you can run it on less but you will definitely suffer a performance hit. If you like to have many applications open at the same time and switch between them - more than 512MB is desirable. Having between 1GB and 1.5GB of RAM is very healthy - and many have been surprised at how having "enough" RAM increases performance. Using CL2 (over the more standard CL3) RAM can yield a 5-8% increase in RAM performance. It's small, but you'd be surprised at how you notice little things like that. When I switched from 1GB of CL3 RAM to 1.5GB of CL2 RAM my computer was suddenly noticeably "snapper". And programs like Photoshop really started to fly.

Graphics card. These days we are starting to consider the graphics card as a second processor. Think about it, there is an enormous amount of processing work that has to occur in order to display the visual material of modern interfaces and GUI rich operating systems such as Mac OS X. Now, with the introduction of "Quartz" - this is even more so. A fast, powerful graphics card slotted into that AGP slot can do wonders. I replaced the stock nVIDIA Geforce 2 with an ATI 8500 Radeon 64MB. With double the VRAM and the graphics processor and memory operating at nearly twice the speed (mine clocked at 300/300) - it makes using my Quicksilver much more of a pleasure. Everything loads a lot quicker and graphic intensive applications don't choke...

After those hardware items have been attended to, adding a faster optical drive and adding connection PCI cards such as USB 2.0 can be of benefit. Both of what I have done. As you can see from a hardware perspective there isn't much left to tinker with besides the CPU. (I"m planning to eventually pop in a dual CPU upgrade - but unfortunately I'm not made of money!) I love my Quicksilver and over this last weekend have performed cooling enhancements/mods including a opening up air holes, installing a fan controller, and more efficient fans. I'm happy to report that my Quicksilver is much quieter and the temperature inside the case never gets over 30C anymore.

In terms of keeping Mac OS X in order - I  back up all of my working files on to another drive and re-install Mac OS X on the boot-able RAID every 4-6 months. This ensures that the operating system never gets buggy and keeps it mean and lean. Over time you learn not to install everything (except what you need) which keeps the system performing faster and more effortlessly. I routinely run cleaning utilities such as Disk Utility, Mac-Janitor, Panther Cache Cleaner (yes, haven't got to Tiger just yet...), and TechTool Pro. Regardless of whether your hardware is up to scratch or not, a poorly segmented hard drive and bloated operating system will severely impact on performance. Furthermore, it has become a well known fact that OS X gets faster with each 'major' release, but gets slower with every 'minor'  (point) update. Keeping your operating system clean and functional has always been part and parcel of the Macintosh experience. Even with older OS systems such as mac OS 9 - if you didn't keep things clean it wouldn't just get slower, it would "crash". Thankfully we are better off now.

I'm very happy to help people get the most out of their Mac's, however I did originally create this thread to obtain information specific to overclocking a G4 867mhz - and I'm thinking that we might have got a little bit off topic. Yes, as discussed above, many factors influence a machine's performance. And in my case there is nothing else hindering the Quicksilver other than the CPU. The moral of this story is that if other hardware or your software configuration is not operating as well as it could - NO overclock is a substitute.  

> I want to know if anybody out there has successfully overclocked their G4 867mhz to 1ghz?
> Also, is there a utility to downclock the L3 cache in Mac OS X? 
(See original post as to why I would want to do this...)


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## tumbleguts (Jun 14, 2005)

Okay - to clarify what I want to know:

> I want to know if anybody out there has successfully overclocked their G4 867mhz to 1ghz?
> Also, is there a utility to downclock the L3 cache in Mac OS X? 
(See original post as to why I would want to do this...)

It seems that the G4 867mhz _IS_ able to be successfully overclocked to 1ghz but there is a problem with the L3 cache. Because at that speed the L3 cache (1/4 of processor speed) is at 250mhz - and the SDRAM chip is only rated for 250mhz. 
This results in two things; 
a) the L3 cache runs but can be unstable, or 
b) the L3 cache is disabled. 

Most (researched sites) suggested using "Powerlogic CPU Director" to downclock the L3 cache. However the current version of CPU Director will not allow a non-Powerlogic card (like my original Apple 7450) to use the pull down menu to change the L3 cache (in either OS 9 or OS X).

Does anybody if there is an older version of CPU Director available that will allow me to do this - and if so, what version is it, and where can I download it from?
Is there another utility that I can use to change the speed of the L3 cache?


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## tumbleguts (Jun 14, 2005)

Okay - I'm getting good at answering my own questions...

I found this site:
<http://macmod.com/content/view/75/2/>

"While overclocking to 933 MHz was a walk in the park, at 1 GHz an annoying issue appeared: L3 cache was usually not activated at startup, either silently with OS X, or with an alert box with OS 9. At first I suspected the L3 cache chips, but then saw that they were rated for 250 MHz, so that probably wasn't the source of the problem. I then considered raising the 7450's core voltage. A 0.05 V boost was enough to get correct L3 cache activation. Long story short: my overclocked Motorola 7450 CPU had heat problems, and the only solution, save in winter, was to run the Power Mac G4 with the case open, which is inelegant. Replacing fans with more efficient ones wasn't enough; the Quicksilver case's design isn't suited for evacuating lots of heat. So a kind of common mod performed on PC cases, the infamous blow hole, was in order. (A blow hole was added just above the heatsink.) Long overdue update: Unfortunately when came summer, I had to back down to 933 MHz because of the heat... So the blow hole gave me a few more months of gigahertz operation, but not twelve months."

I guess that answers this thread... Summary;
> A G4 867mhz can be overclocked to 933mhz.
> When overclocked to 1ghz - the core voltage needs a 0.05 V boost to allow correct L3 cache activation.
> When overclocked to 1ghz - the processor suffers from heat problems and becomes unstable.


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