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BCLK, QPI and 5850 vid card

  • Graphics Cards
  • QPI
  • Overclocking
Last response: in Overclocking
December 23, 2009 11:08:46 PM

My question is about video card performance, using the ATI 5850.

I am planning a new build on the ASUS P6X58D board, using the Core i7 920 CPU. I see that I would be able to bump the base clock from 133 to 166 to achieve DDR3 1333, keeping the memory multiplier at 8x. But this will also increase the QPI from 4.8 to 6.0 GT/s. The Core i7 965 XE comes with a stock QPI of 6.4 GT/s, so I'm guessing its OK to overclock the QPI to 6.0 GT/s, is that right?

Several forums indicate that the 920 "hits the wall" at 2.67 GHz in terms of FPS, but I can't tell how they pushed the CPU clock. They may only be increasing the CPU multiplier, leaving the QPI at the same setting, resulting in the same number of gigatransfers per second. It seems to me that would produce the same fps result. Or is there really some bottleneck at the X58 IOH chip?

Finally, XFX makes two versions of the 5850 vid card. The Black Edition is overclocked from 725 to 765 in its core clock. What the heck does that mean relative to the GT/s coming from the QPI? Would it be a mistake to overclock the 920 to BCLK = 166 and also use the overclocked videocard? Or, do you need to overclocked videocard to take advantage of the greater number of transfers per second from the overclocked QPI?

More about : bclk qpi 5850 vid card

a c 381 U Graphics card
a c 289 K Overclocking
December 23, 2009 11:28:11 PM

This should help

here's the best settings for 167:

BCLK = 167
Mem Multiplier <> Mem Speed = 8 <> DDR3-1336
Uncore Multiplier UCLK Freq. MH16 <> 2672
QPI Multiplier <> QPI Freq.= 18 (36) <> 6012
CPU Multiplier <> Speed = 21 <> 3.50
December 24, 2009 2:23:49 AM

Thanks, I'll give those a try. The question though is whether the ATI 5850 video card will benefit from the higher QPI frequency (6012 vs. 4800 stock), or alternatively, whether the video card might stutter due to the higher rate of data transfer.