Clock 1.0 Mac Pro Overclock Tool Results?

Discussion in 'Mac Pro' started by xgman, Jul 1, 2008.

  1. xgman macrumors 601


    Aug 6, 2007
    I know there is another thread but I thought maybe just for results to compare:,39038647,39192217,00.htm

    Can anyone who has tried this on a 2008 mac pro post their results?
    I imagine the more ram and the more cores will make it tougher to do, but I am very excited to see how this works on my MP.

    edit: on my 8core 3.2, 3.312 seems to be very safe. Much over that and I get a kernel crash after errors. Overclocking 8 1GB sticks of ram is going to be very hard no matter what. The cpu's could probably go much further even without more voltage.
  2. xgman thread starter macrumors 601


    Aug 6, 2007
    Exclusive: ZDNet overclocking tool enhances performance of Mac Pro

    Downloading and using ZDNet Clock

    ZDNet Clock is easy to install. After downloading, you simply click on the ZDNet-Clock icon to start. Then the chipset and the clock chip are detected. The superuser password has to be entered at this point. The only computers currently supported are those equipped with Intel 5000 or Intel 5400 chipsets. That means all Mac-Pro and Xserve models with Intel processors. If the computer is not recognised the program closes with an error message.

    The console can be used for diagnosing problems. It is to be found under "Applications – Utilities – Console". The ZDNet-Clock messages can be found in the "All Messages" window, see figure 3. When the chipset and clock chip have been detected the application appears as shown in figure 1 and figure 2.

    The main control is the slider control, with which the frequency is set. The left-hand stop is always the standard frequency of the clock chip. "Underclocking" cannot be achieved with the GUI. Three frequencies are displayed above the slider control. "Bus Clock" displays the frequency that is actually generated by the clock chip. The front-side bus is also clocked with this frequency. As current FSBs are four times as wide as the original Intel FSB, Intel always indicates the quadruple frequency. ZDNet Clock calls this frequency the "Marketing Clock".

    If you move the slider control completely to the left, 1333 MHz or 1600 MHz should be displayed there, depending on the model. The "CPU Clock" value should show the standard frequency of the CPU. To raise the frequency you slide the control to the right. You should not overdo it when overclocking for the first time. A good first move is to increase the "CPU Clock" by 10 MHz.

    If you push the slider all the way to the right, to the maximum frequency, and click on the "Apply" button, the computer will certainly crash. The optimum CPU frequency with which stable operation is possible has to be worked out individually for each computer.

    Increasing the front-side bus frequency raises the clock speed of the CPU without having to change the multiplier. The frequency of the Northbridge (MCH) is raised at the same time. So the memory is always overclocked as well. In the case of the Mac Pro, the CPU will normally tolerate higher overclocking than the MCH. As the Mac Pro uses fully buffered DDR2 memory modules (FB-DIMMs), which have error checking and correction (ECC), it is easily possible to feel your way up to the maximum stable overclocking frequency.

    The console is used for that purpose. The "All Messages" window contains not only the messages from ZDNet Clock but also entries relating to corrected memory errors. Immediately after changing the frequency, entries relating to corrected errors will mainly appear, that are designated as a "correctable fbd error" or as "recoverable parity errors". They are caused by the switching of the frequency. The CPU and MCH briefly encounter synchronisation problems. This is normal, and there is no need to worry about it.

    If further memory errors appear in the console after successful overclocking, this is an indication that you have exceeded a stable threshold with the overclocking. It makes sense to carry out a test after switching clock speed. Longer running benchmarks can be considered in this context, such as the prime number search program mprime. If no errors occur for several hours, you can assume secure operation.

    In order to keep the effect of memory errors resulting from frequency switching to a minimum, ZDNet Clock overclocks the computer in steps of 1MHz (FSB). Tests have shown that an increase in the FSB by a large amount and the associated increase in the CPU frequency, for example raising the CPU clock speed from 2800 MHz to 3200 MHz, often puts the RAM modules so seriously out of synchronisation that more bits 'topple' than error correction can pick up. This leads to a controlled crash. The memory modules report the error via NMI, the kernel acknowledges it with panic, see figure 4.

    The result of step-by-step switching is that it takes some time for confirmation to appear after clicking on the Apply button. If you prefer direct switching, this can be selected by ticking the "Use Rapid Overclocking" checkbox.

    Whether the switching can be successfully carried out depends very much on the RAM modules used. The first-generation tester (Mac Pro 1.1) is equipped by Apple with modules from Positivo Informática. In this case overclocking only works in very slow steps. The 2008 model (Mac Pro 3.1) comes with preinstalled Hynix modules. In this case, switching also works with "Rapid Overclocking" turned on.

    ZDNet has also tested modules that do not come from Apple. Tests with modules from CSX equipped with memory chips from Elpida are disappointing. They run the Mac Pro clocked at 2800 MHz at a maximum of 2835 MHz. On the other hand, marginally more expensive proprietary modules from Kingston and Transcend (TS2GAPMACP8U-T) display no problems.

    Problem with standby mode

    After waking up the Mac Pro from standby mode, the clock chip is reset by the operating system to the standard setting, with the result that the computer runs at the standard clock speed again, despite the overclocking frequency. Repeated overclocking with ZDNet Clock also only works again if the kernel extension associated with the utility is first loaded from memory. That can be achieved very easily via terminal, by inputting the following command:

    kextunload -b de.zdnet.kext.overclock

    This bug will be remedied with a later version of ZDNet Clock.

    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.

Share This Page