VisionTek HD 4850 Crossfire Overheat?

Hi! Hopefully someone could enlighten me because I've done tons of research and I cant seem to find the source of this issue. My older gforce card died and since my mobo was kinda meant for ati cards, i purchased two radeon 4850 for crossfire. Here are the PC specs

OS: WinXP Pro 32bit
Processor: Intel E6850 Core2 Duo 3.0 GHZ
Motherboard: ASUS MAXIMUS FORMULA / SE LGA 775 Intel X38 ATX Intel
RAM: 1GB x4 but of course XP only uses three
Power supply 680w

The only new components are:
VisionTek HD4850 x2 (one is the older 1slot model and the other is the newer 2slot) connected with crossfirex

After installing both cards I originally had an issue where they would overheat and pc would just completely shut off, so after a little research I found that the stock fan speed sucked so I adjusted that to around 65% for both cards. Temp seemed to be normal range on both cards, 1slot 4850 was 50C idle and 70C under load. the 2slot 4850 has a bigger heatsink so that was 40C in idle and 50C under load. Both of those numbers I believe are normal depending on the case temperature but correct me if I'm wrong please~

After resolving issue with cards overheating, the processor started overheating to around 70C in idle and would shut down under load. i guess from the increased heat within the case? or maybe a coincidence? Anyway this was fixed by just applying a little thermal grease, then processor went back down to 30C on idle and 45C under load.

With those two issues out of the way, I finally got a chance to use my pc and test my cards under heavy gaming for longer than 5 minutes without it shutting down, only to have it shut down 30 minutes later. After it shut down I checked the temp on the both gpu, one was 70C other was 55C, and the cpu was only at 44C so the heat was normal I believe. I'm thinking it may be the power supply that does not have enough watts to support this machine but 680W is kinda alot and i dont have anything else lying around to try except 400W supplies. Any ideas or suggestions that I haven't tried yet?
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  1. It seems your temp situation has been handled well.

    In order to know if the Power Supply is the likely culprit, we'll need to know it's make & model number and it's age. Also, tell us how many drives (hard disk and optical), fans, as well as additional components are running in the system. It helps to have as complete a system description as possible.
  2. WD500GB SATA
    7 fans, 5 powered directly by psu, 2 connect to mobo
    only other component is a linksys pci wireless n card

    and of course how could i forget to post psu specs originally heh
    Suntec 680 Switching Power supply
    Manuf 2004 but purchased early 2008
    Model: Hammer 300
    AC Input: 100-120/200V-240V 7.0/3.5A 50/50Hz
    AC Output: 100-120/200V-240V 2.0/1.0A 50/50Hz
    DC Output:
    +3.3V +5V +12V -12V -5V +5V sb
    40A 45A 28A 0.5A 0.5A 3.0A
  3. mikansei said:
    DC Output:
    +3.3V +5V +12V -12V -5V +5V sb
    40A 45A 28A 0.5A 0.5A 3.0A

    That Codegen PSU is a much older PSU design. The 3.3V and 5V rails are WAY more than is needed on modern PC's, and their over-inflated 3.3v and 5v amperage is the ONLY reason that PSU is rated at such a high wattage. You only have 28A on the 12V rail, and that is where the graphics card(s), hard drives, optical drives, fans, and other components get their power. I have to say it's just not enough 12V power for your setup.

    For a replacement, I recommend going with something of better quality with a minimum of 50A on the 12V rail (rails combined if multi-rail). I'd suggest searching on, but I don't know your location, so you may not be able to shop there. Antec, PC Power & Cooling, Corsair, SeaSonic, Cooler Master, Enermax, Silverstone, and many other quality PSU makers all have ~600W models that absolutely belittle your current PSU's 12V power output. They're also far more efficient, even at high load and higher temperatures.

    Search for something that also has all the necessary PCI-E power connectors you'll need, whether they be 6-pin, 8-pin, or 6+2-pin combo-fit type. If you need a little help in that department, feel free to ask.

    Edit: 50A might be a bit much, but it's an easy safe point. Something 40A or more should suffice, but the more, the merrier.
  4. +1 RazberyBandit.

    And I would suggest you take one card out while you search and wait for the new PSU to arrive. Older, cheaper supplies often lack protection and can damage or even wreck and entire system if they fail.
  5. Excellent :)

    I have been using only one card in the meantime, the problem doesn't occur with only one card so thats what made me originally think it was a psu issue but thanks alot for the advice!
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