Exclusive: ZDNet overclocking tool enhances performance of Mac Pro

Most PCs enable overclocking through the BIOS. Not so ZDNet Clock: The tool increases the bus clock speed, and thus also the frequency of the memory, only after the operating system has been started. The disadvantage of the former method with many motherboards is that a jumper has to be set if you have overclocked excessively. When overclocking by means of a tool, all it takes after a crash is to switch the computer off and on again. So it would seem that overclocking with a utility is the better option. The problem with the incorrectly running system clock demonstrates that this is not the case under Mac OS.

Safe overclocking with the Mac Pro

On the other hand, one problem that makes overclocking risky on most other computers, namely memory errors, does not occur in the Mac Pro. If you overclock a computer whose main memory does not have error correction, switching the frequency can lead to some serious malfunctions. If the memory errors, which always occur shortly after setting the new frequency, affect a few bits that contain, for example, the code of the file system driver, the result may be the complete loss of hard disk data. If, on the other hand, the computer is overclocked into RAM with the aid of the BIOS before loading the operating system and before shadowing the BIOS, this risk is eliminated.

As the Mac Pro has memory with error correction, overclocking after loading the operating system can do little damage. Either the errors are corrected or the kernel causes a controlled crash. For safety’s sake a stability test should be carried out with mprime after overclocking. As a rule, the memory does in fact drop out before the CPU, but you can play it safe if the stability test compares calculated results with previously known results. The best overclocking results are achieved with ZDNet Clock for the Mac Pro if the machine is equipped with brand-name memory. If you think, Apple modules are overpriced, you should use branded memory such as by Kingston or Transcend. In contrast, the no-name modules also used in the test permit only minimal overclocking.

  • Download ZDNet Clock Tool 1.0 for Mac Pro
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    36 Kommentare zu Exclusive: ZDNet overclocking tool enhances performance of Mac Pro

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    • Am 29. Juni 2008 um 7:09 von Matthew

      Underclocken fuers MacBook
      Auch wuenchenswert waere die Moeglichkeit einen Processor zu underclocken. Die MacBook Pros naemlich laufen sehr warm (deshalb auch sehr laut) unter voller Belastung. Optimal waere wenn der underclockte Rechner eine grosse Aufgabe langsam waehrend der Nacht bearbeiten koennte, ohne dass der Ventilator sich kaputt spinnt.

    • Am 30. Juni 2008 um 15:47 von Gerry Conway

      Unable to download – no file in ftp://ftp.zdnet.de/pcpro/download/swlib/08/ZDNet_Clock.tar.bz2/ directory.
      There is no file in this directory for download.

    • Am 1. Juli 2008 um 12:51 von Arne

      I cant download!

    • Am 1. Juli 2008 um 14:50 von James K. Boodley

      Overclock nicht arbeit mit Mac Pro 3.1
      (nur ein bicien Deutch)

      Ich habe ein MacPro mit 2 x 2.8GHz quad-core Intel Xeon (model 3.1), 4GB RAM, und OS 10.5.3. Overclock nicht arbeit: "You can’t open the application ‚ZDNet Clock.app" because it is not supported on this architecture." Was ist loss?

      Hilfe, bitte. Vielen dank!

      (My high school German is rusty so here’s the English version:)

      I have an eight-core Mac Pro with two 2.8GHz Intel Xeon quad-core processors, 4GB RAM, running OSX 10.5.3. When I try to run Clock, I get the error message "You can’t open the application ‚ZDNet Clock.app" because it is not supported on this architecture." I’ve tried removing the non-Apple RAM I have installed but still get the same message.

      Any help would be appreciated. Thanks!

      Kind regards,

      James Boodley
      (Ithaca, New York, USA)

      • Am 15. Dezember 2016 um 0:02 von mario


        did you solved this problem with ZDnet overclocking because i have the same problem/error message.

        It would be nice if you have the answer for me to solve this problem.

        please let me know if you have.

        best regards,


    • Am 3. Juli 2008 um 16:43 von Matt

      Faster time
      Something to keep in mind when using this, your system clock is going to run fast. That is your time clock will get ahead of itself proportionally to the amount you’ve overclocked your mac pro.

      Just keep it in mind :)

    • Am 3. Juli 2008 um 23:44 von Samos

      OK 2 or 3 times, suddenly won’t work anymore…
      … since I made the "kextunload -b de.zdnet.kext.overclock" trick in a root user terminal. ??? …

      Is there any reverse action ?

      It worked great before, on MP 3,1, I’m disappointed

    • Am 7. Juli 2008 um 11:22 von Per S Jørgensen

      Computer: MacPro 2.1 Crashes
      Can`t take the bus clock to more than 340 MHz before it crashes that`s only 7 MHz up
      ; (

      • Am 11. Juli 2008 um 10:36 von ZDNet

        Bad Ram=Bad Overclocking
        As mentioned in the article, oc depends on the memory-modules. A lot of users do have problems with RAM from OCW when they try to overclock their Mac pro. Apple-Ram is ok for oc. Modules from Transcend and Kingston are even better.

    • Am 9. Juli 2008 um 23:37 von BDJ

      This screws the system clock
      Overclocking my MacPro results in my system clock running too fast. At the end of one day my clock will be 20 minutes ahead.

      • Am 11. Juli 2008 um 10:49 von ZDNet

        Try to reboot
        If you have a MacPro3.1 (2008-Model) you can reboot to get the clock running correct. For earlier version of mac pro there is right now no solution.

    • Am 14. Februar 2009 um 17:34 von dave

      time fix
      if people are worried about the system clock getting out of sync, just run this in the terminal:

      sudo ntpdate -u

      If you download Lingon and make a launchdaemon, you can have it do it automatically every x minutes.

      • Am 28. November 2009 um 21:05 von JUN

        AW: time fix

    • Am 29. April 2009 um 12:00 von Cmyk

      Funktioniert nicht mit MacPro Quadcores (Nehalem)

    • Am 3. Juni 2009 um 21:31 von Mariano

      Mac Pro 3.2 Overclocked at 3.6 working perfect!
      I overclocked my mac pro 2008 generation at 3.6 and works perfect. I will keep trying more, but my question is how to keep the computer overclocked after shoot it down. I mean, do I have to overclock the computer after each time that I turn it off? There is any way to make a permanent overclock?
      Any way,
      Thanks for this tool!

      • Am 5. September 2009 um 23:41 von Enrique

        AW: Mac Pro 3.2 Overclocked at 3.6 working perfect!
        It worked fine until I upgraded to Snow Leopard.
        Now it tells me that it’s not compatible with OS.

        • Am 7. September 2009 um 11:42 von Cyrano

          AW: AW: Mac Pro 3.2 Overclocked at 3.6 working perfect!
          try with kernel 32 bits and after reboot on kernel 64 bits

          • Am 8. September 2009 um 2:24 von peanutplanters

            AW: AW: AW: Mac Pro 3.2 Overclocked at 3.6 working perfect!
            I cant get this to run on Snow Leopard either… any plans for an updated version? Or a work-around for the version check?

            • Am 10. September 2009 um 16:33 von Cyrano

              AW: AW: AW: AW: Mac Pro 3.2 Overclocked at 3.6 working perfect!
              start on leopard
              overclock your computer
              re-boot on snow leopard

              for me start on snow leopard 32bits (default)
              overclock my computer
              re-boot on snow leopard 64 bits (keys 6+4)

            • Am 12. September 2009 um 20:27 von peanutplanters

              AW: AW: AW: AW: AW: Mac Pro 3.2 Overclocked at 3.6 working perfect!
              Boot into Leopard? That’s not possible once you’ve upgraded to snow leopard. And the overclock only lasts until your computer gets powered down.

            • Am 14. September 2009 um 13:10 von Tails

              AW: AW: AW: AW: AW: AW: Mac Pro 3.2 Overclocked at 3.6 working perfect!
              It is possible. The overclock resets only if you shutdown your mac, not if you restart it. Just boot into Leopard, overclock it and then restart it through Snow Leopard.

              I use it that way and it works. Although I have encountered some kernel panics on Snow Leopard at overclock speeds which didn’t give me any trouble through Leopard before. So you’ll probably need to do the tests again if the machine is stable through snow leopard.

            • Am 17. September 2009 um 21:32 von xgman

              AW: AW: AW: AW: AW: AW: AW: Mac Pro 3.2 Overclocked at 3.6 working perfect!
              Anyone know how to request the author of this take a look at 10.6?

            • Am 18. September 2009 um 1:44 von xgman

              AW: AW: AW: AW: AW: AW: AW: AW: Mac Pro 3.2 Overclocked at 3.6 working perfect!
              Actually, never mind it works fine in Snow Leopard, at least in 32 bit mode.

            • Am 30. September 2009 um 18:20 von peanutplanters

              AW: AW: AW: AW: AW: AW: AW: Mac Pro 3.2 Overclocked at 3.6 working perfect!
              Please explain how you boot into Leopard after upgrading to Snow Leopard? Unless you have 2 separate installs.

            • Am 30. September 2009 um 18:21 von peanutplanters

              AW: AW: AW: AW: AW: AW: AW: AW: Mac Pro 3.2 Overclocked at 3.6 working perfect!
              And xgman, how did you get it running in 32-bit snowleopard? When the application runs, it clearly states that it only supports 10.5.x

            • Am 4. November 2009 um 3:17 von peanutplanters

              AW: AW: AW: AW: AW: AW: AW: AW: AW: Mac Pro 3.2 Overclocked at 3.6 working perfect!
              Seriously, I am utterly confused… I’ve googled this issue over and over and it seems like I’m the only one with this problem. I cannot get this tool running in 10.6.x AT ALL. I’ve used 32-bit mode, doesn’t work. I dont see how people get this to work UNLESS they have a 10.5.x partition which they boot to run this program. If someone is running this in Snow Leopard, please give me some help on how they got it working.

    • Am 15. Dezember 2009 um 18:44 von Tim

      ZDNET Clock version 2
      Could someone make a 64-bit version of this? It won’t run when my Mac Pro is in 64-bit mode, running Snow Leopard.

      • Am 21. Dezember 2009 um 13:36 von chobar

        AW: ZDNET Clock version 2
        +1 for that

        Seems a shame that it doesn’t work on 64-bit Snow Leopard :-(

    • Am 8. Januar 2010 um 22:41 von stevew

      64-bit bitte
      Ein weiterer Antrag für ein 64-Bit dieses Tool zu kompilieren, bitte. (If only for Folding@home)

      • Am 26. Februar 2010 um 2:49 von Al

        AW: 64-bit bitte
        Could you please advice if it possible to over-clock Mac Pro 4.1


    • Am 27. Februar 2010 um 5:08 von Brien MacDougal

      Please make a overclocking tool for MacBook Pro 13 Inch 2GB ram 2.26 GHz.

    • Am 29. Dezember 2010 um 22:47 von RedEyes717

      kext module is missing – error under Snow Leopard
      Hi Guys,
      I did try all of the methods above, with no success at all.
      I’m under Snow Leopard and I’m keep getting the error ‚kext module is not found ..‘ (from the console messages).
      is there any workaround for this?

      thank you all.


    • Am 7. August 2011 um 21:22 von MM

      Lion + 64 bits
      Any chance of seeing this us full tool ported to compatibility with Mac Os X.7 (Lion)?

      • Am 9. August 2011 um 8:50 von Quicksilver

        Please 64-bit Version for Lion
        This would be VERY apprechiated. I use this tool for years and I love it. BTW: Overclocking in Snow Leopard and restarting in Lion doesn’t work for me.

    • Am 25. September 2011 um 18:09 von Enrico Sbardolini

      A prayer
      I would just like to use RAM at 800MHz instead of 677MHz on both iMac and MacBook Pro Core 2 Duo, 2.4GHz, with 800MHz FSB (2007).

      I think it would be a small thing to do for a utility of this power.

      Thanks, hoping at least one answer.

    • Am 18. September 2012 um 22:13 von Erwin Mul

      64-bit, running a macpro 1.1 on mountain lion (through chameleon) would like to try this.
      I had a freak unintentional overclock to 3.6Ghz from 2.0 after the first run of ML… Geekbench through the roof. Never reproduced it…

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