HD 4870's running hot ... very hot! Could it be the PSU?!?

Question

I bought a new custom-built rig last week ... here are the specs:

Asus Rampage Formula

OCZ Reaper PC-8500 (4 gig)

Q9450 (2.6 GHz)

2 Sapphire HD 4870's in Xfire

Aftermarket cooler on each card: Accelero S1 Rev. 2 (passive)

OCZ Pro Xstream PSU (1000 W)

Vista Ultimate x64

I started monitoring my GPU temps using GPU-Z, and noticed that my idle temps were low (around 60 C), but the "VDDC Slave" temps were all over 100 C, and under stress, they reached close to 160 C.

I started having BSOD and "no signal to monitor crashes" when playing any games so I sent the system back to the company for testing. While I suspected faulty installation of the aftermarket cooler (esp. the VRM coolers), they concluded that it was a faulty PSU, and have upgraded it to a better one. I'm skeptical that this will cure the problem completely.

My question is: Is it possible that a faulty or underpowered PSU can cause such drastic temperatures, and if so, how? I'm going back to discuss it with them later today, and am interested in hearing some advice. Thanks in advance!

Answer 1

Its possible. The harder the PSU has to work, the hotter it gets. That heat can build up in the case, affecting the temperatures of your other hardware. It doesn't matter how good your aftermarket cooler is... if its surrounded by hot air, it wont work effectively.

Answer 2

I know source of your answer

Answer 3

Hmmm. I have the same board running 2 4870s. I show 54 degrees on the VDDC slave right now. Could very well be the PSU was pumping too much voltage into the cards. Cards run warm at idle but dont go up very much even when overclocking or playing Crysis. I'm using a PC Power and Cooling Turbo Power 860 860watt PSU which is made by OCZ. Really something interesting about your PSU. In June when Anandtech did a review of the 4850 cards, that use the same chipset as the 4870, the NV770, they said that OCZ 1000watt PSU couldn't handle 2 4850s:

(first paragraph under the "load power chart")

http://www.anandtech.com/video/showdoc.a...

In the forum I brought it to Anandtech's attention that you only need a 550watt PSU to run 2 4850s in CF and that PSU either had a bad rail or a compatibilty issue with 4850 cards like the Coolermaster 750 Pro has with P35 boards. Althou the PSU is on the certified list for 2 4870s in CF its something to ponder.

Answer 4

No, you need to change the fan to run at a constant duty cycle of 50% or more.

You might also think about putting on an after market cooler since the stock one is pretty lame.

If you elect to go with the after market cooler, make sure you get heat sinks for the memory chips

Answer 5

1. make sure you have both slot tabs on the back of the case removed from behind the cards.  By that I am meaning the tabs that cover the PCI slots you should have 4 removed 2 for each card.  Now my 4870 idled at 80C and crashed, I started reading that you needed to make a profile in Catalyst Control Center and then go into that profile and edit the fan speed % from 15% stock to 60%.  Now I couldn't get that to work, so I plundered around and happened to come across that my ASUS 4870 has an additional software package called SMART DOCTOR, there I found you could change the fan speed and also make it do what it needed to in accordance to the heat of the GPU's.  I am not sure about Sapphire cards whether they have any tools like that or not, but the fan speed does have to come up to cool that card.  And for the numb nutz that claim you need an aftermarket cooler, mine is running 48C all the time even after 4 hours of running Flight Simulator X...  No a PSU isn't going to change the heat...