Bitcoin Forum

Ok, so at the moment I have the following:

2500k
AsRock z68 Extreme 4 motherboard
1 SSD
3 HDD's
2 x 5870's overclocked to 975 core and 320 mem

That is running from a Corsair AX750 PSU (80plus) - http://www.anandtech.com/show/4011/corsair-ax750-80plus-gold


As my motherboard has 3 PCIE16 slots, I'd ideally like to add another card (probably a Sapphire 5850 Extreme).   My question is, can my power supply handle it? :D

Just wondering if anyone has tried anything similar on a 750W PSU?   I have the advantage of having a good, efficient PSU, but still I'm not sure if it'll handle it.

Thanks!!

EDIT:  I've also just realised that my PSU caters for dual graphics cards (ie, it has 2 PCIE cables, both with dual plugs at the end).   I'm not sure how I'd add a 3rd card as I'd need another 2 PCIE plugs for them...   can you get molex to PCIE adapters or something?

Yes you can get Molex to PCI-E converter plugs.You can usually find these in the package of your GPUs.If not,you can buy them for little money from practically any computer shop (online or retail)

As it looks like you heavily OC your cards,I'd recommend an upgrade of PSU to be on the safe side.

Most cards can use at least 200W,A Radeon HD6990 can use as much as 450Ws (when the switch is in Overclocked position on hte board itself),normally its about 300W I think.Radeon Hd6990 is basically 2 GPUs on 1 board,so getting 2 radeon HD6990s ould give you 4 GPUS.

Since you plan to add another GPU,I'd strongly recommend upgrading your PSU to a higher wattage.Anywhere in the (at least ) 850W range wouldn't hurt.I'd say in your case,you'd benefit from a 1000W PSU,that way you can have 4 cards with heavy OC (except for the Radeon Hd 6990 cards,as they suck down power like no tomorrow and need an even beefier PSU to run them)

I hope my advice helps you

Doing some math at the moment you're draining about 450-500W from 12V line. Adding a 180-190W for the 5850 O.C. leaves you with only 40/60W on 12V rails. Not a good idea (disks use 12V too)
Using molex adapter is OK as long you try to use short cables and good quality ones: 190W are 16A, if the cables you use thick wires you can damage them, or ever start a fire.

you're going to be cutting it close. if the cards weren't overclocked i'd say yes but with overclocking like that you're best off looking into getting at 900w+ PSU

That's my recommendation to the poster :-)

because GPUs,especially when overclocked are power hungry hogs (well mine certainly is esp with unlocked shaders and heavy OC)

Fair enough, thanks guys, I think I'll just forget it and stick with what I have.    I've only had the Psu a couple of months so can't really justify upgrading it right now.


Shame I didn't know about Bitcoin back when I bought it :D

The Corsair should be able to handle another 5850, especially if you don't clock the hell out of it.

I was drawing about 275VA on a 5870 924/308 stock voltage with a standard 80+. So actual draw is about 220W. Adding a Sapphire 5850 Xtreme and swapping to 750W 80+ Silver PSU took me to 470VA with the 5870 at 930/310, 5850 at 924/308, actual draw about 438W or 218W for the additional card and CPU 1/3 load due to updating to the bugged Catalyst 11.6B, so that makes the 5850 about 200W overclocked or 160W at 725/300.

So estimating from that (since running only one of my 5870 or 5850 at those clocks reaches the same 303~305W at the wall), I'd say a stock clocked 5850 would bring your system total to roughly 600~650W. Even if all of that was +12V, it's 87% of the AX750's +12V capacity. Pushing it but still within safe limits I would say.

Well, recklessness and impulse buying are my forte, so I went and ordered an AX1200 from Amazon last night :D   Oops :)