Computer Shuts Off with Games (seems related to hd4870) *fixed*

I recently upgraded my rig, only keeping a couple of old components (See below).

I am on my second hd4870, the first was the MSI model and the replacement is the Asus model. At first I thought I just had a bad card... but I was wrong.

During heavy loads, like Crysis for example, after a couple of hours of playing, the computer shuts itself off. It goes Black, and the power cuts completely. Then the comp reboots itself after a brief respite. This only happens with the 4870 installed, as I have tested this with 2 Crossfired 1950GT's, and not been able to replicate.

(Keeping my system specs in mind) I believe my problem is one of three; either my card is over heating (I read it can handle up to 90c before being in danger, but I never break 75c & Idle at 48-49c ), I am starving the system of the appropriate ammount of power, or my Ram is being driven to a limit it cannot handle. Then again, it may be something I am totally missing.

Please, help me figure this out. I already RMA'd one card, I would like to avoid damaging this card, or being forced to wait another 6 days for a replacement

Mobo- Asus Rampage, formula http://www.newegg.com/Product/Prod [...] 6813131284
Processor- Q9550 (may be eating too much power?) http://www.newegg.com/Product/Prod [...] 6819115041
VGA- hd4870 http://www.newegg.com/Product/Prod [...] 6814121277
Ram- A-data 1gb x 3 (about to be 4) ddr2 800 (yeah I know, cheap ass ram)
PSU- Thermaltake Toughpower 750w (not enough juice?) http://www.newegg.com/Product/Prod [...] wer%20750w
HD- 300gb Velociraptor
Msc- 3 low powerd fans, stock heating setup on everything but the the q9550.

BEFORE YOU ASK- All drivers are up to date! Latest Bios! Does not only occur in Crysis, happens with all manner of video intensive software, such as 3dmark. GPU settings are stock. Nothing is OC'd on the system.

Thanks in advance!

Sounds like a PSU related issue, but 750 watts is more than enough. You specs load will take around 450-500 max. Can you try swapping another PSU from a friend?
Next thing I will look into is the RAM. Would borrow a friend's RAM and test it out with just 1 bank only.

Is your rig OC'ed?

DVD drive idle is like... 5-8 watts only....lol
Take your vga card to a friend's house and try it out then.
A Q9450, 4GB ram, 2 HDD, 4870x2 crossfire uses around 550/600 watts load. - off the wall is 800
So your PSU is actually fine. Might be a problem with the amps on the rails.

If you want to test the RAM, try using 1 bank of ram only. I've had issues where MemTest works fine, but gaming doesn't.

Well, it wasnt due to the configuration of cables. I wanted to make sure I didnt have anything loose in there.

The current psu is a replacement for the same brand/model, which broke very shortly after I had purchased it almost 2 years ago. Wonder if my thermaltake 750w is up to it's old shinanigans. Has a 5-year waranty parts&labor... I really hate waiting for sh** like that tho. Rather play FO3 in dx10...

I have been running with bios set to default ever since these problems began. I noticed that advanced/advanced chipset settings/memory remap feature was set to enabled. I looked it up, and that feature is only meant for 64bit OS. I am using vista 32bit. I turned it off, but no luck, still crashes after playing for a little while. Is it possible that the default setting could have damaged the card/mobo? (would be the dumbest thing I have ever seen in BIOS if it is.)

I will try obtaining a test psu, but I doubt I will find anyone who even has the minimum requirements for this rig, (without spending $$$).

Otherwise, I will try running memtest on it, see what happens. (making the disk right now.)

Thanks for the replies and ideas. Anyone else have any?

i dont think its ur PSU, i think ur chipset is running hot and the pc is shutting down to prevent damage

After 5 hours of running Crysis, I am happy to report, my problem appears to be gone.

After installing the new antec 1000w power supply, no more random shut down/reboots. http://www.newegg.com/Product/Prod [...] 6817371012

I ran memtest86 for 18 cycles no prob, and heating on the entire mobo has been fine through testing.

The weirdest part about all of this, is that gpu-z shows my hd4870 actually running, over all, lower temps now. I barely broke 60c this time under heavy gfx loads, where as before it would really work that fan to stay around 65c-70c. I still dont like the fact that fan control appears to be largely software reliant, as on boot ups where I was in bios/dos/whatever seems to really heat up the card, showing a temp of 77c when I finally get into windows. Time to find a new heat-sink, but that's a topic for a new thread.

On the old PSU, the PCI-E power cables had a wire in all six of the ports. The new one has only 4 out of the 6 ports wired. Not sure if this has anything to do with it, I may in fact be underpowering my card (pardon my lack of power cable knowledge.)

Everyone I spoke to agreed that my psu should have enough power, except a couple of people who speculated the psu may be having some problems (seems so). I was also told by somebody at fry's, that he would put at least 800w on this rig (seems so as well).

I had already returned the original Thermaltake shortly after purchase, using the manufacturers waranty, as it burnt out after about a month. The replacement it seems, may have had some issues too. Still under waranty, I might just get it replaced and keep it for future self inflicted head aches.

Thanks everyone for the info, and I hope this helps those of you who are suffering from similar issues.

*Please note, I did not get the model with the 6 12v rails, as I had originally stated I would be buying. This one has 4, and works great.