The State of Linux NVIDIA Overclocking

Moving onto a card that can churn out a few more frames per second, we have the Prolink PixelView FX5900XT Golden Limited. The memory modules on this GeForce FX card are Hynix HY5DU283222AF-28 and runs at 700MHz (2 x 350MHz). An after market Arctic Cooling NV Silencer 3 cools the memory and VPU for this card.

In the past, under Windows, we've pushed this card to 464/926 in CoolBits and have run it fully stable and free of artifacts. The stock speed in 3D mode is 390/700. In order to overclock the card while in 3D mode, you must specify to NVClock which program to use. To compare these stock and overclocked results, we used glxgears and ran it for 20 seconds (taking an average of the four frame rates). After compiling the 0.8pre CVS, we were presented with the new NVClock GTK interface. This interface was much more visually appealing than we had seen with the 0.7 on the TNT2. The different menu options available to view are Hardware, nVidia GeForceFX 5900XT, Overclocking, AGP, and VideoBIOS. Unfortunately, when overclocking the card, the GTK GUI limited the 5900XT overclock to 487/875, as that is 25% higher than the stock speed. Knowing we could push the RAM much higher, we resorted to the command line nvclock commands and to specify the 3D program to use. When entering a clock speed higher than 25%, the force parameter (-f) must be used. However when attempting to go much higher than 25%, the screen would lock-up, forcing us to reboot. After tampering with NVClock, we found our overclocking barrier for the FX5900XT to be about 425/850, which is substantially lower than we had expected considering we reached 464/926 on CoolBits. However, after forcing these new speeds, and typing nvclock -i, to display the NVClock information, the core was running at 390 MHz, instead of the 425MHz we specified. The memory frequency however was in tune with the 850MHz we specified. No matter what other programs or frequencies we tried, the core would remain at 390MHz. We imagine this is a glitch with 3D mode overclocking and NVClock, hopefully it will be resolved when 0.8 is finally released.