About Mac Intel Overclocking: Tips and RecommendationsAs overclocking of Mac Pro is now available and other Apple hardware should follow soon, we have decided to provide some tips and recommendations:



A bout Overclocking in general…

- All CPUs are produced from the same fabrication lines and only final validation tests or OEM requests define their clock frequency.

- Intel has historically always defined a large tolerance for the CPU clock speed, giving room for 'safe' overclocking, and in many cases one could gain 30% frequency overclock without playing with CPU voltage.

- voltage is a key point. The higher it is, the higher the CPU will release heat. But the higher it is, and the higher the CPU can be overclocked frequency-wise. However, playing with the voltage could destroy your CPU, so luckily ZDnet Clock does NOT allow changing voltage parameters, so the risk of destroying your CPU with such application are strongly reduced.

- If have been playing with overclocking over years, and many of you have been applying our procedures to boost performance levels of your graphic cards. If theoretically, overclocking might reduce the lifetime of a product, we have never experienced such serious effect, and when we did, it was only in cases where we have been changing/playing wit the voltage too.

- the main risk remains the instability of the overclocked computer, it would be useless to gain 20% raw performance improvement if your computer freezes every 30 minutes!



and Mac Intel in particular

In the past, we mostly played with PowerPC overclocking by modifying the multiplication factor of CPU. For several years, Intel has locked this factor on its CPU, and the only way to overclock such CPU is to increase the frequency of the bus.



Technically, this is much more interesting as all components are then working faster, not only the CPU, but also the FSB, as well as the memory. But on Mac Pro, the latest might quickly become the limiting factor< Indeed, the FB-DIMM is a particular memory format, featuring a controller chips on each module, and this is the limiting factor when performing overclock of the bus frequency, as this chips has a strong tendency to already heat a lot in standard conditions (that’s the reason why FB-DIMMs feature heatsinks).



If you want to try overclocking your Mac Pro, start the procedure and test with only 2 RAM modules installed, with the smallest RAM capacity Only when all test have been successfully completed, then you can add additional modules of equal or larger capacities. You might have also to test all your pairs of RAM modules to define the overclocking limit of each ones.



ZDnet Clock directly access to the chips controlling the bus frequency, so it should be completely transparent for Mac OS X. Only careful test, and especially simultaneous video encoding/decoding will allow you to define figures about performance gain.



Last but not least you will have to pay attention to the Error Correction Code of the FB-DIMM. Indeed, ZDnet Clock will provide a log file of such ECC memory parity which will increase with the overclock. The file is located and entitled: /var/log/system.log. If ECC dramatically increase with the overclock, if the computer seems to remain stable the overall performance might not increase much further as correction of RAM errors will become the main limiting factor especially in memory exchange and addressing. So, when performing the overclock procedure, pay attention to the ECC, and stay below the point where the reports of EEC dramatically increase following an increased in frequency.

(Via HardMac.com.)