Intel P45 to make overclocking more complicated

Posted on Monday, May 12 2008 @ 22:31 CEST by Thomas De Maesschalck
Bit Tech talked to MSI motherboard engineers and Tony Leach from OCZ and heard overclocking will become an increasingly more complicated art. The site says that if you want to overclock on a Intel P45 based motherboard you'll need to master GTL Reference Voltages, CPU VTT and its relation to GTLs, Clock Skews and CPU PLL Voltages to get a stable overclock.
It’s a case of spending a lot of time increasing the CPU VTT (not over 1.35V – you’ll kill the CPU) and CPU PLL (not over 1.7V, because again you'll kill your CPU) and tweaking the GTL Reference voltages for the CPU and North bridge to be around 61-63 percent of VTT for 45nm CPUs and 67 percent for 65nm.

This is particularly noteworthy with quad-core processors because, if you’re finding core two and three drop off under Prime95 load, it’s down to the fact that the two CPU dies are not identical and while core one and four can hit the FSB you’ve set, cores two and three are having trouble. Tweaking the GTL can sometimes give them better stability.

Leach even went as far as to say you’ve got to find points on the board and check the actual voltages with a multimeter, because we’re talking some extremely minute changes and if there are elements of vDrop from the board or vDroop when the CPU loads the BIOS can be inaccurate.

Next you HAVE to play with the clock skews – MSI will have these on its P45 boards, Asus has them on its current X38 and X48 boards, while both DFI and Gigabyte also have them on their X48 boards. Basically as the data has to jump from the front side bus domain to the memory domain this window becomes smaller and prone to more jitter, the faster you increase either the front side bus or memory frequencies and timings. By adjusting the skew you can realign these clock signals and suddenly stability should return again – a good board will have less jitter in its signal generation and finer skew adjustments than one that's not as good.
More info at Bit Tech.

About the Author

Thomas De Maesschalck

Thomas has been messing with computer since early childhood and firmly believes the Internet is the best thing since sliced bread. Enjoys playing with new tech, is fascinated by science, and passionate about financial markets. When not behind a computer, he can be found with running shoes on or lifting heavy weights in the weight room.

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