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Old 08-09-08, 10:49 PM   #36
uber nub
Join Date: Apr 2007
Posts: 24
Default Re: GTX280 stuck at 3d speeds even at desktop.

I believe I understand the reason behind certain problems such as particular clock frequencies and problems related to them. Apparently the G200's use the internal PLL Ref Clock Gen where it can, and where it can't it falls back on the Southbridge PLL Clock Reference which turns out runs lower than the 108MHz reference clock internally. This inturn appears to cause clock calculation errors and resonance in the clock domain for both the GPU and the SB intermittently (sometimes more other times less). It appears I've fixed the problem on mine simply by running PCI-E Frequency at 112MHz. That allows for a small percent of out-of-phase clock correction. Intel SB's generally handle upto 120MHz at most on the SATA bus. 117-118 is safer bet. This will mean increasing the SB voltage slightly to compensate for raise in PCI-E frequency. 0.050-0.075V is more than adequate. If you want to see if this is the problem or not. Set your PCI-E frequency in bios to 108MHz and see if any random weird behaviour occurs. Slow downs, timeouts, graphical glitches, out of sync screen drawing, display adapter not recovering and requiring a reboot, delays / hanging in keyboard or mouse use, etc.

In a perfect world PCI-E at 108MHz would be right, but since at least on my card Nvidia did a poor job of insulating the circuit board electronics from interference, jitter, resonance, etc from external sources it causes more problems for everything else due to the chatter which happens intermittently on the 104-109MHz frequency range.
Asus Rampage Formula X48 Rev 1.xxG 0408 Bios / Q6600 G0 3.46GHz 1724MHz FSB / 4 x 1GB DDR2-1150MHz / GTX280 739/1512/2664 / Coolermaster Stacker 832 / Corsair HX1000 1000W PSU
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