Originally Posted by xxbassplayerxx
In my experience, 3D performance degrades sharply above 222 BCLK. It seems others have been able to validate my findings as well.
To be clear, what we confirmed in testing earlier in this thread showed that it wasn't BCLK per se, but rather QPI speed.
Noting that QPI can be run at 22X (and 24X) as well as at 18X, I lowered the BLCK and increased the QPI multi. Sure enough, you get the same massive 3D performance drop right around where QPI crosses 4000 as measured by CPU-Z (8000 in bios). In this case, it dropped at 182 BCLK for me with QPI set to 22X (Yielding 4004 QPI in CPU-Z). There was a little fuzziness - approaching in 1mhz inc, I was able to delay the drop until 183, but not repeatedly. It's roughly the same.
Not having another 1366 board in hand to try, I can't be sure it's an Asus only thing (or RIIIF only thing) - or even that it's not a CPU thing since it's a QPI issue. However, it seems likely to be board specific, and it seems to be an artificial limit. I am curious to know what happens when 4000 QPI is crossed in another board (Gigabyte for instance), just to nail this thing down.