PCGH: Micro stuttering on multi GPU solutions

[weeds]

nvidia does ?
they don't !

there is a tool that let's you choose the profile, but that does not come from nvidia.

Anyway, you can change it with Ati by just renaming the executable... it's really that easy.

You can choose any of the SLi rendering modes ( Single GPU, Split Frame rendering, AFR1, AFR2, SLi8x, SLi16x, SLi16Q, SLi32, SLi32Q AA ) right from the NVCPL. You can set any of the modes globally or change the mode in any existing profile. As Saaya said you can also create profiles and choose any mode. No third party tool needed. Nvidia also has a load balanceing on screen display that is very helpfull in seeing what mode works best. There was a time when you couldnt change modes in the NVCPL but that was long ago,in the 6 series. Nvidia offers far more accessibility, control and tweakability over SLi then ATI and Crossfire. ATI talked about adding the same type of user contol in CCC over a year ago but it has never come to pass. A shame really.

Renameing executables also disables any app specific fixes and optimizations. Really not an acceptable way to get a game working right.

SLi Modes available in NVCPL

[v_rr]

I think that some games look to have slutter but the problem is that the second core goes to 2d cloks -> 3dclock ->2d clocks -> 3d clocks and that provoque slutter.

There are some games that happens that and actually it look simple to resolve that clocks problem.

[saaya]

cadaveca, please calm down, if there is anybody from amd/ati reading this thread your only scaring them off from posting and maybe offering to help with your comments.

afaik the data isnt sent twice to both cards in sli/xfire, its more like raid where both cards receive the same set of data.

[KoHaN69]

Talking about filming it, I think if a CRT (120Hz+) with a high refresh rate is used the footage would be more revealing.

[Eastcoasthandle]

For those with X2's have you tried this

[Jungle+=]

It works on all rv 670's and 680's. The only thing im not sure about is if it affects both cards.

[Dirtbiker14519]

I figure I would bump this thread before it gets too old, as I have just gotten into Crossfire (I sold my 8800GTX for 2 HD3870s, worst decision ever ), and have noticed the "micro stutter" in Crysis.

I usually hang out at Guru3D, and I made a thread there seeking a solution for the problem. I recieved an interesting reply:

I have seen this first hand I build about 2 systems a day. I sell customized systems on e-bay and at a local shop so i mess withem a bit before they go out. Some allow you to change your BIOS PCIE speeds to match each other for example the current system i'm on I can run PCIE at 4X matched or 8X matched. it does allow 16X X 8X but the system will only run it at 8X by 8X. But even on this system when I run 8X by 4X micro stutter is very appearent. So thats why I asked you to try it. I have tried 16X matched with no performance difference than 8X by 8X i did not even notice performance difference at 4X matched. When the buses are matched there is no stutter. I thiink it's only when you get to ultra high resolutions will there be a performance hit. So it's just from my experiance but I could be wrong but so far with every system I have seen mismatched PCIE speeds the Micro stutter is more appearent if you had a HD 3870 X2 as well you would see that even though crossfire is enabled the micro stutter is not appearent. So this is just theory on personal experiences.

Source: http://forums.guru3d.com/showthread.php?t=257553

So it looks like this issue might be more prevalent in systems that run at
16x/4x PCE-E bandwidth such as the P35 or P965 chipset?

[L7R]

Hey, nice find! I have P35 so that could be why there seems to have people who doesn't recognize it?
Oh, Welcome to the forums! And sorry about your loss (8800GTX).

[L7R]

Seems your first priority is to get rid of those awful 8.3 cats. Downgrade to 8.2 if you haven't already tried? At least it should help those corruption issues. Remember to use drivercleaner (in safemode) after uninstall AND reboot.

[Dirtbiker14519]

I don't get any curruption in Vista x64, but I will take your advice and try them out in XP (although I hate to install old drivers).

Lets try to keep this discussion on topic though, as the micro stutter is my main concern .

[STaRGaZeR]

For those with 3870X2s, if you're overclocking make sure your cards have the exact same clock in both core and mem. I had this issue, but sometimes all was good. I figured that the two cores had to be at the same clocks to work in armony. If not, micro stuttering appears.

BTW, have you tried the lastest 8.4 beta to see if the second core is always at 3D speeds? That was one of the greatest problem I experienced when I had the card, and it seems it's now fixed.

[Dirtbiker14519]

Yeah, the 8.4betas (aka the 8.3 hotfix) didn't help at all .

[Katzenschleuder]

The lack of interest into this serious matter really makes clear how this community is driving into a totally wrong direction.

Thousands of threads about making SuperPI and 3DMark runs, but fewer and fewer about things that matter for stuff that computers are there for.
This is like spending most of you time tuning your car engine to produce the most possible RPMs in the garage, while not caring about the fact that it won't drive faster than a Fiat Bambino on the road.

It is really sad to witness such a waste!

[Dirtbiker14519]

@Katzenschleuder: Theres not much we can do man. Everyone who has this problem probably sent a ticket to ATi informing this of this problem, and other than that all we can do is wait.

[Katzenschleuder]

The problem is that this issue gets close to zero attention in the community and media compared relatively to unimportant news like a 3DMark record that tops the previous one by a couple hundred points, or a new CPU that is 3% faster than the previously fastest!

This issue kills 30% and more of the effective frame rates with SLI/Crossfire systems in most game scenarios! Not just with some hardware setups, but with ALL of them.

Thats more than 30% of your money spent on SLI/Crossfire cards TOTALLY WASTED!
And all we see in conclusion is a hand full of articles of German speaking websites.

That's totally insane!

[Dirtbiker14519]

I agree, but like I said unless someone has contacts to ATi or nVidia engineers, theres nothing we can do.

Oh, BTW, I mentioned earlier that I had a problem with microstuttering in Crysis with 2x 3870s and a P35 board, and I got it verified by ATi engineers that the P35 is the culprit. Unfortunately I am not in direct contact with the so I can't get further information.

[Katzenschleuder]

and I got it verified by ATi engineers that the P35 is the culprit

He was wrong based on ATIs own words. Both - ATI and NVIDIA - claim that it is caused by a kernel space timer issue in the OS.

[KoHaN69]

Well, can we get someone with two 3870s and a P35 to switch to an X48/X38 board?

Redawgc187's mismatched PCIE speeds hypothesis makes sense.

[Dirtbiker14519]

Someone already did on rage3d (i think). If I can find the post i'll be sure to post it.

[Dirtbiker14519]

Update: I found it .

http://www.rage3d.com/Board/showthread.php?t=33912003

Post #9 includes what most of us want to see .

[Katzenschleuder]

Update: I found it .

http://www.rage3d.com/Board/showthread.php?t=33912003

Post #9 includes what most of us want to see .

All what this guy wrote is empirical evaluation that has no value.
The problem is measurable and exists with all hardware setups.

Again, this has nothing to do with the mainboard used for sure.
ATI and NVIDIA confirmed the problem and both said that it is related to a kernel space timer/scheduler problem in Windows.

The problem is that this issue exists SINCE YEARS and was NOT FIXED.
So we finally need some big media attention on this issue, because it kills most of the real performance that we expect from SLI/Crossfire by evaluating FPS measurements in hardware reviews.

[cadaveca]

Well, can we get someone with two 3870s and a P35 to switch to an X48/X38 board?

Redawgc187's mismatched PCIE speeds hypothesis makes sense.

But it's not correct, I have the exact same stutter from 975x, 965, RD600, P35, and X38. I got so many boards from trying to sort out the issue, in the end with no success.

when this thread originally started, my tickets were simply closed by ATI. NOw that is not the case; I've had some good contact from them, and I feel confident that a fix will happen.

[generics_user]

i can confirm that on 16x/4x the stuttering gets much worse, while it is there i only get one barely noticeable stutter in 5 minutes on the X16/x16

i also tried CF in the X4 slot (x16 physically), average fps didn't drop that much but stuttering gets worse-

my cards also have different sock clocks and when i don't sync them with CCC the stuttering gets worse

in my opinion the whole stuttering problem is a flaw in the idea of SLI/CF which seems to get worse when mismatching cards/clocks/LINKS

EDIT: i'm using XP64 so i can try xp and vista tomorrow if you want too, maybe there is a difference between different OS

[KoHaN69]

But it's not correct, I have the exact same stutter from 975x, 965, RD600, P35, and X38. I got so many boards from trying to sort out the issue, in the end with no success.

when this thread originally started, my tickets were simply closed by ATI. NOw that is not the case; I've had some good contact from them, and I feel confident that a fix will happen.

So what what operating system and what environment does this occur in?
XP 32bit?
XP 64bit?
Vista 32bit?
Vista 64dbit?
Linux 32bit?
Linux 64bit?
(I don't think there are sli drivers for mac)

[Katzenschleuder]

This problem can be reproduced consistently on all Windows versions.
Does SLI/Crossfire work on any other OS?