Would I benefit from adding a 2nd HD5870 in my x4 Slot?

[LifeOnMars]

I'm currently running 1 HD 5870 and gaming at 1920x1440 and 2048x1536 resolutions. Not having any major problems with games quite honestly apart from the obvious titles which are more GPU demanding. Would I see any major benefits, framerate wise, in adding a second card?

I only have a spare x4 slot on my mobo as it's only the P8P67 standard edition. Therefore it would be running in x16 and x4 mode for the crossfire setup. What sort of performance hit would it be as opposed to a full x16/x16 or x8/x8 setup?

HD 5870's are relatively cheap in the UK now so money is no major biggie other than the fact it may not actually give me any gains?

I think my PSU would be enough to power the two in crossfire with my setup but what do you guys reckon?

Or, do you think I should just wait for an all new uber card around the time Battlefield 3 is released?

Look forward to your input people

EDIT - I play alot of BFBC2, would like a boost in Metro/Crysis as well etc. As I say, the usual candidates.

 

[cadaveca]

I don't think it'd give enough to make a difference, TBH.

You will quite literally only get 1/2 of what you would using 8x8 wit hthe second card..so say in 8x8 you'd get an extra 20FPS..you'll only get 10.

Mind you, the last time I tested was on 775...

 

[LifeOnMars]

I don't think it'd give enough to make a difference, TBH.

You will quite literally only get 1/2 of what you would using 8x8 wit hthe second card..so say in 8x8 you'd get an extra 20FPS..you'll only get 10.

Mind you, the last time I tested was on 775...

Yeh, that's what I was thinking. Very tempting to try it though, just for shits and giggles.

Would it allow extra image quality if nothing else, such as more AA? Just thinking it would be worth picking up a dirt cheap one to try out. I suppose I could always flog it on if it doesn't work out.

 

[Mussels]

yes, you would get a large difference. i wish people did research before offering bad advice.


will edit link in with details shortly.


http://www.techpowerup.com/reviews/AMD/HD_5870_PCI-Express_Scaling/1.html

while this was with a single card, it shows that 4x @2.0 bandwidth is enough for a 5870 - so therefore, it wont hamper crossfire performance either.

 

[cadaveca]

You know, to be honest, I'm not too sure how good newer drivers will work. I did not work well for me, at all, as it introduced some "stutter" I just couldn't deal with.


And now I don't have 2 5870's...just one. I suppose I could toss in my 6950's, and see what's up, but becasue Crossfire scaling is a far differnt thing for them, I don't think it'd really tell ya much.

See, thing is, it depends on the rendering mode, because if each card does alternate frames, the lack of PCIe bandwidth is going to make the card on the 4x slot have issues jsut getting the frames up to the master card. And it's more than just rendered frames that goes form card to card...

Most signel cards, @ 4x, don't show much of a loss, but Crossfire is much different, as the cards need not only to communicate with the CPU, they also need to talk to each other, and the Crossfire Bridges jsut don't provide much bandwidth for the res you are running.

yes, you would get a large difference. i wish people did research before offering bad advice.


will edit link in with details shortly.

You could drop the attitude, there Mussels. I've tested, like i siad, on 775, and no, it did not work well. It's not bad advice...you need to do your own research, brother.

 

[Mussels]

You could drop the attitude, there Mussels. I've tested, like i siad, on 775, and no, it did not work well. It's not bad advice...

w1zzard himself tested it. your 775 problem was related to the CPU not having enough power, not the slot bandwidth.

 

[cadaveca]

w1zzard himself tested it. your 775 problem was related to the CPU not having enough power, not the slot bandwidth.

W1zz tested Crossfire? It's not the same as running a single card.


AMD has even admitted, that for high resolutions, 4x links are not enough. 3870x2 is the perfect example

 

[Mussels]

W1zz tested Crossfire?

he tested the 4x slots to see if they hampered anything, and i personally tested crossfire with them as well. i had less than 5% increases from 16x/4x to 16x/16x, and only had boosts when i OC'd the CPU (and that was a 4.3GHz wolfdale, still CPU limited)

 

[cadaveca]

You were running 1920x1440 and 2560x1600? I'm sorry Mussels, but you do not understand what the problem is. The problem is NOT PCIe bandwidth from CPU to the cards. It's the available bandwidth from card to card.

 

[Mussels]

and while its mostly still relevant, w1zz did do SLI scaling tests on 580's.


http://www.techpowerup.com/reviews/NVIDIA/GTX_480_PCI-Express_Scaling/24.html


again, no real difference.

 

[cadaveca]

Sli is NOT the same inter-card communication as Crossfire is.

 

[Mussels]

Sli is NOT the same inter-card communication as Crossfire is.

i'm telling you (and the OP) i've tested it, and had the results i've given. there is no performance loss at 4x @2.0


if you dont want to believe it, fine. but at least let the OP make up his own mind. i've at least given some evidence to back up my case. you havent.

 

[LifeOnMars]

Awesome. As I say, they are pretty cheap anyways so it should be fun trying it out. I'm seeing that a 600w PSU is needed for HD 5870 crossfire so I should be OK on the PSU front right?

Will post benchmarks with and without crossfire at 2048x1536 when I get it. (If I beg the missus that should be within the next week)
Either way I'm gonna go for it.

 

[LifeOnMars]

Don't sweat it, if I get crap performance gains, I can always sell it on

OOps, . meant to edit the last post not post again, sorry Mussels

 

[cadaveca]

i'm telling you (and the OP) i've tested it, and had the results i've given. there is no performance loss at 4x @2.0


if you dont want to believe it, fine. but at least let the OP make up his own mind. i've at least given some evidence to back up my case. you havent.

Don't take my word for it. you didn't even read my posts, did you, where i said the situation might be far differnt now than before, as I tested on 775? Man, some nerve.

ran X16-X4 at first on this setup i have now. Ran fine. increase in performance for sure. not as good as X8-X8 but still better performance than 1 GPU

 

[Mussels]

Awesome. As I say, they are pretty cheap anyways so it should be fun trying it out. I'm seeing that a 600w PSU is needed for HD 5870 crossfire so I should be OK on the PSU front right?

Will post benchmarks with and without crossfire at 2048x1536 when I get it. (If I beg the missus that should be within the next week)
Either way I'm gonna go for it.

go easy on the AA at 2048x1536, you'll run out of Vram on 1GB cards. i managed 5870 crossfire on a 600W for a while and it ran fine, but it shut down if i ran furmark (never in games, even BC2) - so avoid the overkill stress testers.

 

[cadaveca]

Oh, BTW, if those x4 lanes are off the southbridge, they are only half speed on some boards, so equivalent to a x2 link.

No matter for P67 though. they will come off the southbridge though. I mean, I got the same board here, I could fire it up and tell you how 6950's scale.

 

[Mussels]

Oh, BTW, if those x4 lanes are off the southbridge, they are only half speed on some boards, so equivalent to a x2 link.

almost got it


its that on some boards they run at 4x 1.0, and not 2.0 - so yes, half the bandwidth/equal to 2x @2.0

 

[cadaveca]

No, mussels, they are half-bandwidth 2.0. Remember, I'm the motherboard reviewer...knowing such things is my j-o-b. they are PCIe 2.0, 2.5GT, on P55-based boards.

 

[LifeOnMars]

Oh, BTW, if those x4 lanes are off the southbridge, they are only half speed on some boards, so equivalent to a x2 link.

No matter for P67 though. they will come off the southbridge though. I mean, I got the same board here, I could fire it up and tell you how 6950's scale.

That would be great Dave. Very interested to see the results.

 

[cadaveca]

Give me two shakes to fire up the rig. What game would you like me to use?

 

[Mussels]

No, mussels, they are half-bandwidth 2.0. Remember, I'm the motherboard reviewer...knowing such things is my j-o-b. they are PCIe 2.0, 2.5GT, on P55-based boards.

not impossible for them to cheap out on the links. afaik it was just that they ran 1.0 links at some point along the way, screwing with the available bandwidth even if the 'slot' was 'rated' at 2.0

 

[LifeOnMars]

Give me two shakes to fire up the rig. What game would you like me to use?

A couple perhaps mate. BFBC2 and Crysis 1 if possible.

BTW you two are killing me with your toing and froing. Would love to be sitting in a bar with you two having this discussion / argument

EDIT - Here's how it reads on the Asus site for my mobo but it is adjustable in the BIOS. -

*The PCIEX16_2 slot shares bandwidth with the PCIEX1_1 slot, PCIEX1_2 slot and USB3_34 connector. The PCIEX16_2 runs at x1 mode by default for system resource optimization.

 

[cadaveca]

not impossible for them to cheap out on the links. afaik it was just that they ran 1.0 links at some point along the way, screwing with the available bandwidth even if the 'slot' was 'rated' at 2.0

No, we already has this discussion on here, it's what's different from P55 to P67, really, and why the drives and USB 3.0 can be slow.


For example, the P7P55D-E that I reviewed featured a PCI-E switch to provide full bandwidth to the USB 3.0.

Check it out for yourself, the stuff's on the manufacturer's pages and in Intel whitepapers.

A couple perhaps mate. BFBC2 and Crysis 1 if possible.

BTW you two are killing me with your toing and froing. Would love to be sitting in a bar with you two having this discussion / argument

Just a discussion. Doesn't bother me one bit. Mussels and I do this quite often, it's how we show our love for each other.


It wil ltake me a bit to get the Crysis into my STEAM on the other rig, but numbers for both coming up.

 

[LifeOnMars]

No deeper love than techie love

Nerds and our words huh