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To: Joe NYC who wrote (256337)	9/25/2008 9:11:58 PM
From: pgerassi	Read Replies (1) \| Respond to of 275872

Dear Jozef: Sounds like the nVidia BIOS has a hysteresis plus a very quick onset to full fan speed. At low fan speeds, the GPU heats up real quick, thus quickly passes the high speed set point in the GPU temp/fan speed curve plus on the upside no hysteresis is applied. At that point you get 100% fan speed. Then as the temperature drops as the heat rate being sunk exceeds the production, the hysteresis keeps the fan from dropping its speed to match the temperature. This keeps the fan speed high until the hsyteresis period is over. When it happens, the temperature is below the lower set point and the fan reduces to your manual setting. Where upon the temperature quickly increases again and the cycle repeats. What the AIB or GPU BIOS maker should have done is flatten the curve so that the fan speeds gradually up as the GPU temps rise. The slope should equal what the GPU at max TDP given the HSF thermal mass causes the temperature to rise. Thus the fan speeds up slowly and allows the GPU to find a stable operating point given the load. Hysteresis is not needed when the slope is low enough. The only problem with that is that even at low loads the fan is spinning faster than what the HSF needs at that GPU temp to keep it there and thus is noisier than what the competition does at the same HSF size. That is the price for a stable system than what results from the typical oscillating system. The other way these things work is that the nVidia GPU needs lower GPU temps to work right. With a smaller delta, the onset has to be fast or else the max GPU temp limit is exceeded due to the fan accelerates slower than the temp rises. This can be fixed with a lower high speed fan setpoint or by increasing the thermal mass of the HSF. The latter results in a heavier GPU and bulkier card than the competition. ATI GPUs though tend to have higher maximum temperature limits. This increases the delta to ambient and allows for a smaller heatsink or a slower fan to deliver the operating temperature even with a higher thermal power output. Thus even with higher power usage, the ATI board could be quieter than the nVidia ones. It is also the reason why the 9600GSO may offer the same performance as a 4670, but its power usage is higher and it is bulkier than the 4670. If it is so bothersome, perhaps you should send it back and switch to a different brand or GPU. Check the reviews before you buy. They may steer you away from annoying examples. Or you could go to an aftermarket HSF combo. Pete