I've seen this problem come up time and again and I was wondering whether there is a different approach to it. Yesterday I bought and installed a new graphics card in an attempt to moderately upgrade my PC. The new card is an ASUS built ATI HD 5450 (the precise model is Asus 5450 Silent). Everything is all fine and well until I start playing a game, any game at all. The screen starts distorting and flickering uncontrollably making it impossible to play a game. I tried uninstalling and reinstalling the 10.6 drivers (didn't work) I checked for a missed power supply to the card (there is no external power supply to it) and then I tried down-clocking the card. I had read that a simple reduction of 25 Mhz should work (the memory is clocked at 800 so I tried 775) but I had to reduce both GPU clock AND Memory to 500 MhZ (via Catalyst Manager) for this to work. After the down clocking everything works fine but I didn't pay for a 500 MHz clocked card!! Is there anything I'm missing here or should I return the card back?
I'm writing this from the office so I don't remember my PC stats but I do have a 650W PSU so that shouldn't be an issue.
Haven't done that but neither the screen nor the cable gave me any trouble whatsoever with the previous ATI card I had onboard. Besides, what would the monitor or the cable have to do with the fact that everything works when I lower the clock speed on the GPU and the card RAM?
Thank you all for the replies. Yes it was most likely a heat problem, the service guy from the shop that I bought the card said so after having tested it. Since this card doesn't have a dedicated fan of it's own (has a heatsink instead) it can cool itself less efficiently than a card with a fan on it. Since I live in a country with a rather warm summer (Greece) the ambient temperature is allready around 30 C and this compounds the problem even further.
The service guy said it probably had a faulty heatsink (or so he said) and refunded me . As for my tower, I thoroughly cleaned it before installing and I do have 3 fans installed (that's as many as it will hold) in it to help with the airflow. My cables are all tidy and strapped together to keep clear from the fans. The temperature of the card never rose above 46C (or so Catalyst Manager told me) and I don't think that's an extreme temperature.
I bought a TwinTech GTS 250 Green Ed SVGA (nVidia based) which sports a massive fan on it. Will install it later today, see what happens. My old card ATI based card (HD 2600 Pro) had a dedicated cooling fan on it and never once failed me.
I still can't help thinking though that it might have been faulty overclocking by the manufactorer which causes this card to malfunction. I read a lot of threads here about ATI HD cards which need to have their clocks tweeked downwards for them to work properly.