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MacPro Overclock


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WHAT? Of course that there's an overclock, read again, he changes the fsb of the xeon from 1066 to 1333, so in that way the cpu clock comes from 1.86GHz to 2.33GHz....that's it an 25% more of perfomance dude!

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I think Core 2 processors are locked to work in single CPU mode only, unless you find some hardware workaround to enable it to register as a Xeon to enable physical multiprocessing. After that, it's all up to the CPU features and if it's entirely compatible in operation with a Xeon... good idea though, I might want to read up more if that's even possible ;)

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  • 11 months later...
Do you have a download link for that?

It's on the page he linked. I just tested it and to my surprise, it actually works.


Mac Pro (early 2008)

1x 2.8GHz Quad Core Xeon



Geek Bench

2800MHz: 5471

3150MHz: 6191

3220MHz: 6417 - unstable

3270MHz: No boot


I didn't test any settings long enough to determine if they were stable or not. I know 3220 is unstable since I got a kernel panic within 5 minutes. If there's a kernel panic, or the computer won't boot, the computer will automatically set everything back to the standard settings.

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Thanks, I found it.


It does work but system profiler doesn't see the changes.


Is there a way to update the profiler?

Will I have to use OSX86 methods?


GeekBench 2.0.17

Platform: Mac OS X x86 (32-bit)

Operating System: Mac OS X 10.5.3 (Build 9D34)

Processor: 2 Intel Xeon E5462 @ 2.80 GHz

Model: Mac Pro (Early 2008)

Motherboard: Apple Inc. Mac-F42C88C8 Proto1

Memory: 10.00 GB 800 MHz DDR2 FB-DIMM


Speed: Score

2800Mhz: 8005

3003Mhz: 8993

3101Mhz: No test done - failed to reboot

3108Mhz: 9079 - rebooted fine seems stable - keeping this speed - tested under Vista x64 score of 7963 with windows version of GeekBench. CPU-z Confirms clock speed of 3107.9Mhz at peak speed.

3206Mhz: 9184 - Failed to reboot - felt like the best speed improvement.

3402Mhz: 8461 - Failed to reboot

3444Mhz: Instant Kernel Panic


Highest Stock OS 10.5.4 - 3.2Ghz MacPro3,1 @ GeekBench is 10736

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In a rare example of the PC's performance tuning culture translating to the Mac, a new utility has surfaced that lets Mac Pro owners overclock their systems beyond Apple's official specifications.



The German edition of ZDNet has posted a utility dubbed Zdnet Clock Tool that allows owners of the Intel-based Mac workstations to push the clock speeds of their Xeon processors significantly higher -- with leaps from 2.8GHz to 3.24GHz for more recent systems.


Proven to work by those in the Mac Communityin the Mac community, the approach also increases the speed of the system bus and the memory as a result, though Apple's choice of hardware ironically suits it better to the process than many gaming-oriented parts for Windows computers: as the Mac Pro must use RAM with error correction, it prevents an excessive overclock from ruining data on the hard drive by making sure that only valid data leaves system memory.


The clock difference is enough to provide a tangible "free" upgrade in performance to the systems, though this isn't always measurable. In synthetic tests such as Geekbench, the software can incorrectly report similar performance even though timing the results proves that they're above what would happen at Apple's officially rated clock speeds.


However, unlike most overclocks, the technique requires a certain degree of trickery and carries an extra amount of risk. The current version of the tool works by loading a kernel extension into Mac OS X on boot that forces the clock speeds upwards immediately after the system starts. Without it, the Mac Pro would immediately revert back to its stock speeds the moment the system is rebooted, according to ZDNet. The initial beta app can also sometimes be overridden when the Mac comes out of sleep mode.


Like most overclocking, the technique is also limited by the nature of the hardware. At present, the German experimenters are unable to push past the 3.24GHz barrier without an inherently unreliable system. The faster processor speeds eventually overwhelm the memory and prevent it from correcting every error, triggering a kernel panic in Mac OS X that forces a reboot. High-performance third-party memory that operates above spec is described as the only real solution to this problem.


System time also falls out of sync without the expected clock rates and can't be corrected even by calibrating the computer online, the testers say. Instead, a reboot is necessary to at least temporarily provide accurate timekeeping.


While very much a beta version and potentially dangerous -- the possibility exists that the system won't start up correctly -- the utility is the first known that modifies core system performance on Intel-based Macs. Until recently, most overclocking utilities for Macs have dwelt on ramping up clock speeds on video cards to eke out more 3D performance for games.

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Guys, I have a question for you folks. I have installed leopard on my office HP xw8400 workstation and it works perfectly stable. Right now it has 2 GHz Intel Xeon 5130 on one cpu slot (the other is empty, which may be sometimes I will think of filling). I came across people overclocking xeons as well. Of course, the above mentioned zdnet overclocking utility (for mac pro) would not work for osx86 machine. Is there any other way it could be done. The thread link at the top mentions about putting a tape over 6th pin on last row. Is that all is required? I have read at other places that two pins may be required.

here is one for 54xx


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