Previous 1 2 3 Next 33 Replies Latest reply: Jul 2, 2008 8:43 PM by Ecker
heycarlos Level 1 Level 1 (0 points)
Well, they claim you can OC a 2.8GHz mac pro to 3.2GHz safely using this utility.

I've downloaded the app and will post results as soon as I can.

One caveat -- no performance improvement in Xbench (or other benchmarks) but the article seems to address this and suggests a stop watch to see the real-world performance gains since the Mac clock is tied to the system clock.

From the article:

+Unlike Windows, Linux and many Hackintosh versions, Mac OS uses the bus clock speed as the time source. It is compared with real time when booting up. Nor does time correction by means of the Mac OS NTP daemon succeed: It simply no longer works with a large discrepancy between the bus clock and real time.+

+Whereas programmers of the IBM PC XT had to be forgiven for using the bus clock speed because of inadequacies of its Intel 8253 timer module, it should be reasonable to expect more from Apple, who now only offer computers with modern HPET timers. After all, multimedia applications use the HPET module. So videos do not run faster after overclocking.+

+The only option for "normalising" the time of the Mac Pro again is to restart without switching off the computer. ZDNet Clock is fundamentally "reboot-proof". But there are a few snags. The latest series of the Mac Pro (Mac Pro 3.1) can indeed be overclocked in the ZDNet test up to 3241 MHz while remaining stable. But a reboot without crashing is only possible up to 3178 MHz. Carefree overclocking fun does not exist beyond this frequency.+

Here is the article and download to the utility:,39038647,39192217-1,00.htm

Mac Pro 8-core 2.8GHz, Mac OS X (10.5.3)
  • Philip Scherzinger Level 1 Level 1 (5 points)
    I have a Mac Pro 2.66GHz (MacPro1.1). I do indeed suffer the problems not being able to reboot when changing the clock speeds, but I still did some testing with this tool.

    I was surprised that I am able to clock this computer up to 3.20GHz while being incredibly stable and reporting no parity errors. I could even clock it up to 3.28GHz which is the max and there are no sudden kernel panics, just some parity errors on one of the memory modules I installed.

    I have 6GB of RAM, with 2GB originally coming from Apple.

    This looks promising and I look forward to future updates. Glad to see that the newer Mac Pro's have success even when rebooting.
  • EdZeke Level 1 Level 1 (0 points)
    My Geekbench 2.0.17 32bit specs & results:

    MacPro dual quad-core 3.0
    OS X 10.5.3
    16GB RAM (TransIntl RAM)
    Nvidia 8800 GT 512MB RAM

    Overclocked to: 454 bus, 1816 Marketing bus, 3405 CPU Clock
    Rebooted fine
    Geekbench result after overclock: 10294
  • Louis M. Cohen Level 1 Level 1 (140 points)
    How do you get yours to reboot again normally? I tried the utility but don't want to use it anymore, and now my Mac Pro won't reboot unless I shut it down completely; during a standard reboot the sleep light pulsates and nothing happens.
  • Philip Scherzinger Level 1 Level 1 (5 points)
    It's been noted that the first version of Mac Pros (MacPro1.1) with Dual-Core chips cannot reboot. They must be shut down, and then can be started normally. However, this resets the clock speed back to defaults.
  • asbissonnett Level 1 Level 1 (5 points)
    I am unfamiliar with this type of utility and have a question. I have the 1st gen. mac pro running 10.4.11. So, by using this utility is there any potential harm that can be done to the computer due to overworking it, and what are the chances? Also how hard would it be to set up?
  • Ludacrisvp Level 1 Level 1 (60 points)
    You would need to upgrade your operating system to Leopard in order to use this utility.
    That would be Mac OS 10.5.x
  • Matthias Wahl Level 1 Level 1 (100 points)
    I have the "Original" 8-Core Machine (MacPro 2.1) with 3.0GHz.

    Runns fine till 374MHz (Bus Clock), 1.498 MHz (MB Clock) and 3.374 MHz (CPU Clock). But I'm not able to reboot at any speed but the original one

    I use 4GB Apple RAM... an wondering if it could be possible to use the (new) 800MHz RAM as well...? Maybe this would solve the problem...? At least could give me a higher range to overclock my Bus Clock...!?

    Does the new RAM work with my machine, or am I stuck with the 667MHz models...?
    For example - my old G4 500 Dual uses 100MHz Bus Speed and works well with 133MHz RAM...
  • Phil108 Level 1 Level 1 (0 points)
    Tried the app.
    Just freezes at launch.

    Own a MacPro Dual-Core 2.66 (MacPro1.1) with 8GB RAM.

    No idea why.
  • lunelson Level 1 Level 1 (0 points)
    Hi Philip,

    I have the same model as you (Quad 2.66, MacPro1,1), I read the notes on ZDNet and I'm curious about what this means "not being able to reboot" --

    does it mean that once you overclock, the reboot command doesn't work? Or that it causes a crash?

    Are you forced to do a hard shutdown each time (pressing and holding the power button)?

    If one has to do a hard shutdown then I guess I can't use it. It will throw all my RAID 1 volumes out of sync.
  • The hatter Level 9 Level 9 (60,880 points) would restart before using it in Safe Mode, to make sure everything is clean and as few startup and background processes run.

    I didn't follow my own advice and ended up having to spend an hour with Disk Utility and Disk Warrior cleaning up my own mess

    .... but, it did run, and I could inch it up ever so slightly, not enough and obviously not something I'll do again for awhile.
  • ZeB (France) Level 1 Level 1 (0 points)
    One of the main author of the well known website MacBidouille succeed to overclock until 3.7GHz ! (and it looks stable)

    Screenshot :
  • kentech Level 1 Level 1 (0 points)
    Christopher, thank you for this smartly-designed utility. But before I experiment anywhere near the edge for my 2.8 MHz 2008 Mac Pro, I would love to understand a couple of things:

    (1) Over a warm Restart, or alternately a cold boot, how are the overclocking parameters retained (or not)? Is the kext in the temp directory the source? Do the parameters NOT survive a cold restart. Which leads to . . .

    (2) If one goes a bit to far out on that limb and the Mac goes wonky, how does one safely reboot into the original speed settings? I.e. how does one recover instead of another reboot into a crash? Or do the parameters NOT survive a cold reboot?

    Is that why the overclock.kext is in the private/temp/ directory? Does it get deleted on cold boot?

    I guess a little more detail about the locations and inner workings of the utility's generated files would be nice to have and would increase my confidence.
  • Philip Scherzinger Level 1 Level 1 (5 points)

    Once you overclock and reboot, the power light will flash rapidly and will not start up. You have to hold to power button to manually shut off the computer. Once you do this, your computer will start up normally, but the clock speed is reset back to default settings, which is 2.66GHz for you and me.

    Only the newer Mac Pro's which were released in early 2008 will be able to reboot, as of now. I saw some mention of the author of this program looking into a fix for our models?
  • TV Pete Level 1 Level 1 (55 points)
    I tested this interesting little utility earlier, but unfortunately my Mac won't go above 2.84GHz before it falls over. I have tried this 4 times and the second time it froze at just 2.828GHz. The other failures consisted of the screen greying from the top, and the machine informing me it would need to be restarted. The fourth attempt I increased the fan speed to 50% (extremely noisy in the very quiet environment I live in!), and it went to 2.842GHz before it just froze.

    I was running the console throughout, and saw no warning of the impending failures.

    I have 8 x 1GB RAM, so all 8 slots are filled, and the utility I run under widgets always shows significant temperature differences between the memory slots, not huge, about 20ºF. The memory consists of the 2 original Apple 1 GB sticks and 6 x 1GB from OWC.

    If it's not clear, this is the Jan 2008 model MacPro3.1!
    I'll try taking out the extra memory later today and retesting to see what happens

    Message was edited by: TV Pete
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