Bottlenecking 5870s/PSUs

StopNotWorking

Would a Q9550 @ 3.6Ghz bottleneck crossfired 5870s? Also would a 750w Corsair TX be enough to pull them? The CPU is undervolted to 1.2V and it's 100% stable at it so it's not pulling anything over stock. Only 2 HDDs attached as well

I've heard people saying it would work and others saying it wouldn't so I thought it would be best to have a bit of a banter over it

deceit

I've got an i7 930 overclocked, 6gb ram 3sticks, 2 hd's with one 5870 running easily on a 600 watt psu. The max they consume is between 188watts. I've also had it running with an overclocked e8400 on a 500watt psu so it should be fine once not much other stuff is put in to draw power.
The below is taken from there site
"500 Watt or greater power supply with two 75W 6-pin PCI Express® power connectors recommended (600 Watt and four 6-pin connectors for ATI CrossFireX™ technology in dual mode)"

lmimmfn

deceit wrote: »

I've got an i7 930 overclocked, 6gb ram 3sticks, 2 hd's with one 5870 running easily on a 600 watt psu. The max they consume is between 188watts. I've also had it running with an overclocked e8400 on a 500watt psu so it should be fine once not much other stuff is put in to draw power.
The below is taken from there site
"500 Watt or greater power supply with two 75W 6-pin PCI Express® power connectors recommended (600 Watt and four 6-pin connectors for ATI CrossFireX™ technology in dual mode)"

How are you testing the consumption? if you look at this admittedly very handy chart a 5870 consumes 148-200Watts on full load - http://mark.zoomcities.com/images/gfx/GFXpowerchartbybrandgen.png

OT: Im not sure about the improvements to power consumption of the 930 over the 920 however a 4.1/4.2Ghz 920 is supposed to consume about 270Watt( and my electricity bill definately points in that direction lol ). A very good 600W PSU rated at 85% effeciency can sustain a constant 510Watt( unless your PSU is quoted as 600W @ 85% effeciency? ). 200W for 5870, 270W for OC'd 930 and youre damn close to unsustainable power required from your 600W PSU.

I have my 920@4+Ghz, 3 gig ram, Xfi sound card, 7 harddrives, 5850 OC'd + 8800GT OC'd, DVD drive plus 5 or 6 USB devices and i would say im easily on the 600W mark on full load. Im sure i have other stuff connected also just cant remember lol.

OT and to OP - it depends on the PSU and the amps on the 12v rails tbh. a corsair 750W should easily be capable of running 2 5870's.

The 9550 will bottleneck them @ 3.6Ghz. I had my 5850 on a system with a Q9550@4.1Ghz and moving to i7 i got around 5-15% performance improvement( mainly on min FPS but max FPS also went up by about 5% ). So 2 cards will definately bottleneck, its a known fact that SLI/Crossfire setups on i7 are the bomb as the extra memory bandwidth of the i7 benefits( i5 not so much due to the x8 PCIE when in dual card setup ).

Solitaire

lmimmfn wrote: »

a 5870 consumes 148-200Watts on full load - http://mark.zoomcities.com/images/gfx/GFXpowerchartbybrandgen.png

Pics that I can view or it didn't happen

But seriously, even the TDP is ~160W and in practice they rarely stay around there for long. In most games that aren't Crysis a HD5870 probably doesn't draw much past 100-120W (average) under full 3D load. A 200W result is either heavily OCd, peaking abnormally high under a GPU-killer bench like Perestroika or just plain wrong. Or a bit of each.

A very good 600W PSU rated at 85% effeciency can sustain a constant 510Watt

No. A "very good" 600W PSU can sustain at least 600W. Otherwise its RMA Time. Of course, the 12V capacity would vary anywhere between 100W and 600W depending on topology; generally a "very good" PSU would be using VRMs and could tug 564-588W on the 12V rail(s) alone.

Komplett-Tech: Ryan

If you want to get picky, a very good 600w psu will be alot closer to 800w, Corsair are well known for this with their 1kw being a 1.28kw psu and their 1.2kw being a ~1.5kw jobbie.

deceit

lmimmfn wrote: »

How are you testing the consumption? if you look at this admittedly very handy chart a 5870 consumes 148-200Watts on full load - http://mark.zoomcities.com/images/gfx/GFXpowerchartbybrandgen.png

OT: Im not sure about the improvements to power consumption of the 930 over the 920 however a 4.1/4.2Ghz 920 is supposed to consume about 270Watt( and my electricity bill definately points in that direction lol ). A very good 600W PSU rated at 85% effeciency can sustain a constant 510Watt( unless your PSU is quoted as 600W @ 85% effeciency? ). 200W for 5870, 270W for OC'd 930 and youre damn close to unsustainable power required from your 600W PSU.

I have my 920@4+Ghz, 3 gig ram, Xfi sound card, 7 harddrives, 5850 OC'd + 8800GT OC'd, DVD drive plus 5 or 6 USB devices and i would say im easily on the 600W mark on full load. Im sure i have other stuff connected also just cant remember lol.

OT and to OP - it depends on the PSU and the amps on the 12v rails tbh. a corsair 750W should easily be capable of running 2 5870's.

The 9550 will bottleneck them @ 3.6Ghz. I had my 5850 on a system with a Q9550@4.1Ghz and moving to i7 i got around 5-15% performance improvement( mainly on min FPS but max FPS also went up by about 5% ). So 2 cards will definately bottleneck, its a known fact that SLI/Crossfire setups on i7 are the bomb as the extra memory bandwidth of the i7 benefits( i5 not so much due to the x8 PCIE when in dual card setup ).

It wont give out 510 watt, it just mean that it will take the extra 15% on top of the 600 to generate 600watt. I havent came accross any psu other than nameless brands and ocz that only give what they state. The corsair 750 he has will be giving him at least 800watt unless something is wrong with it. I've an xilence one which is 80 rated and was outputting 720 full draw, (maybe just got lucky with it) more than my 780watt ocz which was erratic over 700watt. Had them tested in my old job as my psu was giving me problems (ocz one).