SLI Not performing as expected.

tommybhoy · 11 Dec 2011 at 23:05

Maybe your 650w PSU doesn't provide enough wattage causing the cards to lose power?

http://www.guru3d.com/article/geforce-gtx-570-sli-review/13

Surveyor · 11 Dec 2011 at 23:05

@ Mackey18

You've gone a bit overboard with your signature, 4 lines of text only.

Are you playing BF3 at 2560x1440?

The resolution doesn't seem to have been mentioned so far.

Mackey18 · 11 Dec 2011 at 23:10

Tommy those drops are due to the Benchmarks changing not due to power drops.

Surveyor, yup 2560x1440. And I'm changing my sig.

I just can't work out why performance is so bad. I don't believe that the CPU can be so limiting.

Mike

Surveyor · 11 Dec 2011 at 23:14

Why don't you try it with just 1 GTX 570 and then see what difference it makes adding the second.

Mackey18 · 11 Dec 2011 at 23:18

I don't really have the time now, but ok will try that. Could I not just disable SLI and see, creating the same effect?

Mike

tommybhoy · 11 Dec 2011 at 23:23

Ok, then your gpu's are scaling fine.

Yes turning off sli would achieve the same thing.

But before you try that as you are running on 2560x1440, try BF3 with everything ultra, except switch AA Defered to off and see if your fps improve.

If there is an improvement then it's vram related.

Sasahara · 12 Dec 2011 at 02:34

I would guest it's Vram and PSU related, you really need more vram as bf3 on that res can use up to 2.5gb as some people have seen with their 3GB 580's.

Running sli GTX570's on a 650 W, even a decent one will be on the limit, this could have a slight effect on performance maybe -5%.

Combining alll issues, Vram being the main one + the no overclock that seems to be the reason.

The SLI was working as expected on 3D Mark, it's low just because of the no overclock.

Threepwood · 12 Dec 2011 at 02:43

Silly question time

have you got V-sync on or off?

Drop the clock down to 4GHZ imo, temps will be fine then.

You should be able to check the Vram suggestion by running the game in a lower resolution and comparing one and 2 cards.

jonnylaris · 12 Dec 2011 at 03:44

WTF 650W PSU for 570SLI? That's just crazy dude and its definatley your problem!

You need MINIMUM 750W for 570sli, i would however recommend 800+

Threepwood · 12 Dec 2011 at 05:03

^^ ha! well spotted, obvious is obvious!

Mackey18 · 12 Dec 2011 at 05:30

So you guys thinks it the v-ram on the GPUs not getting enough power? Surely if it's only a 5% decrease its not our main problem, but ok I'll buy a new PSU at some point.

Cheers guys,
Mike

Mackey18 · 12 Dec 2011 at 06:29

If this is simply down to a lack of VRAM, I'm slightly upset, as I spent over £1000 and I can't even play BF3 on max. Are there any tricks I can do? I think I read somewhere that if VRAM is completely used, system RAM can act as a buffer.

Mike

MeatLoaf · 12 Dec 2011 at 07:54

I dont think its lack of vram as my pair of 470s run BF3 on ultra no probs at all at 1920@1080. May be a problem if youre on a higher res.

Lack of overclocking on the CPU will be the main culprit i think

Mackey18 · 12 Dec 2011 at 10:49

Well I'm on a 2560x1440 display but yea you're right I think it's the CPU and possibly the power supply, so I'm going to buy CPU cooler and a new 800w PSU for next week. I'll then OC my CPU to 4.6GHz and see how that goes. If that doesn't work, I'll be distraught.

Mike

Lunawolfy · 12 Dec 2011 at 12:32

Surely running 1.5G cards at that enormous res on max just isn't happening! Severe lack of VRAM at that massive res.

Stick the res down to something more human (1920x 1080/1200) and see how that goes

James J · 12 Dec 2011 at 12:42

Lunawolfy said:
Surely running 1.5G cards at that enormous res on max just isn't happening! Severe lack of VRAM at that massive res.

Stick the res down to something more human (1920x 1080/1200) and see how that goes

Vram has sod all to do with BF3 though as it uses a mesh system which calculates LODs on the fly based on your available Vram. This is regardless of the lowest or the highest settings. If it was metro 2033, I'd agree on a potential vram issue, but not with BF3 as it'll just use whats available and change the LOD on the fly.

Threepwood · 12 Dec 2011 at 12:55

Vram has sod all to do with BF3 though as it uses a mesh system which calculates LODs on the fly based on your available Vram.

/grabs popcorn.

garsands · 12 Dec 2011 at 13:12

shadesofgrey said:
/grabs popcorn.

I was about to bite, but luckly I stopped when I saw your post

arc@css · 12 Dec 2011 at 13:17

+1 in respect of psu.

tommybhoy · 12 Dec 2011 at 13:19

James J said:
Vram has sod all to do with BF3 though as it uses a mesh system which calculates LODs on the fly based on your available Vram. This is regardless of the lowest or the highest settings. If it was metro 2033, I'd agree on a potential vram issue, but not with BF3 as it'll just use whats available and change the LOD on the fly.

How do you explain the differences with the 2 6950's when 4xMSAA is applied?

It's probably going to be an even wider gap in CrossFire, especially higher than 1080p.

It's simple to find out with the op, as suggested earlier, try the game using both the settings above, if there isn't a problem with high settings, but there is with 4xMSAA, then he has his answer.

1.5Gb vram's the sweetspot with BF3, any less and you begin to struggle on full ultra, especially @2560x1440.

(The popcorns in the micro

)