Now that you can purchase a 9800GX2 for less than $300, I decided to jump on board as it’s dual-GPU is capable of the same horsepower as two 8800GT’s in SLI mode, but requiring less heat and less power.
Preliminary folding numbers for this beast is about 5500 PPD on a single core. If you run it in SLI mode, the GPU client will only use one of the two GPU’s. When set to multiple monitor mode, folding on both cores produces in most cases over 10,000 PPD
Guides to folding on multiple GPU’s
In regards to Windows XP – you can run 2 clients by just disabling SLI-mode
In regards to Windows Vista – you will need to have 2 monitors plugged in (1 on each gpu) for the separate gpu’s to be recognized. One user has posted work-arounds, in case you don’t have extra monitors around.
Two things of note regarding the power requirements for this card.
1) You’ll need (1) 6-pin PCI-e power connector AND (1) 8-pin PCI-e power connector
Most new PSU’s are starting to include an 8-pin PCI-e power connector, but if you don’t want to spend $150+ on a new 700W+ PSU, then you can buy an adapter from BFG that does the trick (fits perfect on the EVGA card as well), just be sure you have at least (2) 6-pin PCI-e connections, and a GOOD QUALITY (good amps, good efficiency) PSU.
2) You DO NOT need a 700W+ power supply like nVidia states.
My system includes a Core2Duo E8400 cpu @ 3.0Ghz, 2x dimms of memory, 3x hard drives, dvdrom, and the 9800GX2 all on an Enermax Liberty 500W Power Supply (w/ 8-pin adapter). Using my Zalman ZM-MFC2 fan controller (that reads power as well). My idle power is at 215W, and under 100% cpu & gpu load, reaches only 290W. Now with a good quality 500W power supply (with 80%+ efficiency & 20 amps on each rail) you should be just fine. Though results may vary.