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Started by thrifty_shopper | | 7 answers
Graphics card not recognized -- need new PSU?
I've inherited a PC at work, but I can't get the included graphics card recognized by Windows 7 and it doesn't produce any output. Even though a collegue stated the setup worked before, I think the PSU is underpowered.

CPU: AMD Athlon II 935
Mobo: Gigabyte GA-MA785GMT-UD2H
GPU: AMD HD 6990
PSU: OCZ 500W (two 12V rails)

I tried the card in my home PC (650W PSU). On bootup (before driver installation), the fan spun to max rpms twice (I'm guessing once for each GPU on the card). It produced output and was recognized in Windows (drivers automatically downloaded). So the card works.

In the work PC, the fan spins, but doesn't spin up to max rpms during boot. Since the fan also spins without the PCI-E power plugged in, I'm guessing it's not receiving enough power. The PSU has one 8-pin PCI-E power cable and there is a 2-molex to 6-pin PCI-E power cable plugged into the other 8-pin power connector. The BIOS is set to use any PEG (PCI-E) graphics first, then the integrated graphics.

I'm going to try putting another graphics card in the work PC to ensure the PCI-E slot works. If it does, am I correct in assuming the PSU is underpowered and I should buy a 600W, single-rail replacement?

Thanks.

Update: I tried with a HD2600 and it works fine, so I think the card is underpowered. I'll use the onboard video now and keep an eye out for a good quality 650W (or so) PSU on sale.
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a b ) Power supply
a b U Graphics card
October 15, 2014 9:51:32 PM

thrifty_shopper said:
Thanks for your input. I found a Corsair Ax760 760w Module Psu on sale. I know it's more than I need, but it was $30 on Amazon.ca! I bought two. :-)


All late, but no problem :)  you have more than enough to crossfire. The chart I used earlier actually was the total wattage it drew for the system adding up to 400 watts on load with full rig, adding another 150 gives up to 550 total, but it's bad to have your PSU working hard all the time since it reduces it's life span. The AX is a tier one PSU so you are perfect :) 
October 15, 2014 4:24:56 PM

Thanks for your input. I found a Corsair Ax760 760w Module Psu on sale. I know it's more than I need, but it was $30 on Amazon.ca! I bought two. :-)
a b ) Power supply
a b U Graphics card
September 18, 2014 6:23:37 AM

Tradesman1 said:
TDP is like 375 on the card alone, AMD recommends 750 as did Guru3D in a review they did

http://www.guru3d.com/articles-pages/radeon-hd-6990-rev...


http://www.xbitlabs.com/articles/graphics/display/radeo...

The card alone actually draws in 400 on load, so then I have no idea how he powered those cards on his other RIG o-o, here is the charts and here are the benchmarks. "AMD recommends" means they assume you have some No Name uncertified PSU running in your RIG
a b ) Power supply
a b U Graphics card
September 17, 2014 7:14:06 PM

Tradesman1 said:
A 6990 normally calls for a min of a 750 PSU



Isn't that for a no name brand PSU? And they usually draw a TDP of 300 watts.. So together they will need around 650 watts. Or maybe 700 watts, but one card doesn't need 750 min lol.
a b $ Windows 7
a c 132 ) Power supply
a c 212 U Graphics card
September 17, 2014 6:46:26 PM

A 6990 normally calls for a min of a 750 PSU

Best solution chosen by thrifty_shopper

a b ) Power supply
a b U Graphics card
September 17, 2014 6:38:16 PM

thrifty_shopper said:
I've inherited a PC at work, but I can't get the included graphics card recognized by Windows 7 and it doesn't produce any output. Even though a collegue stated the setup worked before, I think the PSU is underpowered.

CPU: AMD Athlon II 935
Mobo: Gigabyte GA-MA785GMT-UD2H
GPU: AMD HD 6990
PSU: OCZ 500W (two 12V rails)

I tried the card in my home PC (650W PSU). On bootup (before driver installation), the fan spun to max rpms twice (I'm guessing once for each GPU on the card). It produced output and was recognized in Windows (drivers automatically downloaded). So the card works.

In the work PC, the fan spins, but doesn't spin up to max rpms during boot. Since the fan also spins without the PCI-E power plugged in, I'm guessing it's not receiving enough power. The PSU has one 8-pin PCI-E power cable and there is a 2-molex to 6-pin PCI-E power cable plugged into the other 8-pin power connector. The BIOS is set to use any PEG (PCI-E) graphics first, then the integrated graphics.

I'm going to try putting another graphics card in the work PC to ensure the PCI-E slot works. If it does, am I correct in assuming the PSU is underpowered and I should buy a 600W, single-rail replacement?

Thanks.


The cards maybe underpowered, it also depends if your PSU is CFX/SLI ready, but in any case it would be good to another 650watt PSU, but get a bronze certified one. You should be fine. Also if you add the math. Each card draws 150watts. 150+150=300+ the tdp of CPU which is 95=395+ the HDD and everything else probably around 450-470 or the like, but if your PSU is probably a no name brand and not 80+ it won't produce the desired output of wattage, so it would be best to upgrade. But test the PCIE slots first.

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