before my friend buys a graphics card from me, I suggested we test it out in his tower. The card (a 9800 GTX+ with one 6-pin power connector) fit in the case, but we had trouble finding enough power plugs. His power supply doesn't have a 6-pin connector, but an adapter came with the card that substituted two 4-pin connectors (the plug color was white) for the 6-pin. His power supply only had one 4-pin connector. We plugged that in and the 6-pin into the 9800 GTX+, curious to see what would happen. The computer started up well enough, the 9800 powered on (the fan was running), and it went to desktop just fine. Problems occurred when we tried to run a game. We started up minecraft (just to see), and there was lag when he went into open areas.
I'm curious whether or not having a half-powered graphics card would possibly damage the system or the card. Thanks for reading all this!
The PSU may not be able to provide enough +12V amperage (even though that GPU doesn't need too much). What brand and model, not just wattage, is his PSU? A quality modern PSU has full range active PFC (no little voltage switch) and 80+ certification for efficiency. If his PSU is just some cheapie that came in a case, it probably isn't up to the job, regardless of how many watts the label claims it can produce. Seasonic, Antec, Corsair, and Enermax are among the quality brands in the 430W-550W range you would want to consider.