Ideal power supply for this system


Apr 30, 2012
Hey there, people of Tom's Hardware.

I've read your power supply recommendations in your sticky and I'm getting mixed opinions between yours and other sites with similar guides - so of course I'm wary. You see, I have a friend who built a computer some time ago. There were several problems with the computer when it was built, but those boiled down to a misplaced CPU and a random piece of software causing DPC latency that disappeared without a trace.

However, he then bought an AMD HD Radeon 6850 - specifically the XFX brand. It requires a 500w power supply, and has a single PCI-E power connector requirement. However, he bought a Corsair CX500 and the computer would randomly turn off at different points during usage. Power supply issue, we thought! He bought an OCZ ZS 550w. Same issue occurs. The only similarity between the two power supplies are they have roughly the same amount of watts on the 12v rail, despite one being 500w and the other being 550w.

We have exhausted many possibilites now, including that of the card being at fault (we tried his card in my computer with an OCZ GameXStream 850w). We will be trying his computer with my power supply tomorrow, and since we've exhausted pretty much every possibility, we're expecting to need yet another new power supply. So what would you guys recommend?

Full system specs:

AMD Phenom II x4 840
4GB DDR3 1333MHz Single-Channel
XFX AMD HD Radeon 6850
500GB 7200RPM Barracuda
DVD Drive
ASUS AM3 Motherboard.

Thanks in advance.


The HD 6850 should pose no problem for either of those PSUs. I think you need to look elsewhere for the problem. The HD 6850 only requires 125W at maximum use (something you would rarely reach) at +12V. That calculates to 12.4A on the +12V rail. The Phenom II x4 840 is only a 95W processor, so it won't add that much to the load. Allowing for the normal +12V devices usually found in a system, a 500+W PSU of good quality should not be an issue.


Apr 30, 2012
But then what would be the issue? I mean the card works fine in my system of higher wattage (i7 920, 6GB DDR3, 850W GameXStream PSU), and his older graphics card the 5570 works fine in his computer. It's only when the graphics card is put in that we get regular turn offs at weird points - and we've tried reinstalling drivers from scratch and the like. There isn't amazing airflow in the case, and it is quite a compact case for the components (the 6850 is an absolute pain to get in because of the space constriction) and the PSU does get reasonably warm during use, is it possible that the PSU is getting too hot because of high strain/bad airflow and is reducing the wattage it can output? If so, what would be the logical solution?
Check the system event log and see if there is an error associated with the shutdowns. You can also modify the restart/shutdown behavior so that you get the BSOD instead of a shutdown. Google the error code and let us know what the error code is...i'm betting event id 41.

Modify the restart behavior for the computer. To do this, follow these steps:
- Right-click My Computer, and then click Properties.
- Click Advanced system settings.
- Click the Advanced tab.
- In the Startup and Recovery section, click Settings.
- Click to clear the Automatically restart check box.

This will let you get the BSOD when your computer reboots/shuts down. To check for errors on previous shut downs you can check the system event log:
- Click the Start button .
- In the Search box, type Event Viewer and hit enter
- In the list of results, double-click Event Viewer.

Either psu shouldn't be heating up ( didn't mention wether 1 or both ) with the load being putting on it by those specs
Take the case side off, point a house fan at the pc and try running it
If it doesn't crash you know you have an airflow/heat problem