Why advantage of SLI, Crossfire, multiChrome is questionable

[Blín D'ñero]

From PC Games Hardware:

Micro Stuttering
Video proof: Micro stuttering may destroy the performance gains from current multi GPU technologies
Why the advantage of SLI, Crossfire and multi Chrome is questionable

The phenomenon

Triple-SLI: Problems with micro stuttering is obvious and cannot denied (Bild: PCGH)Here the disclosed problem starts: multi-GPU systems often do not succeed in displaying regular distributed frames; it comes to large time intervals between individual images - "micro stuttering" - despite supposedly fluid frame rates. One example: frame 1 is followed by frame 2 after 10 milliseconds, which corresponds to a cadence of 100 Fps. Frame 3, however, is to be seen only 40 milliseconds afterwards, followed by frame 4 after 10 ms.

The result is disastrous: The subjective frame rate of a multi-GPU system is in this extreme case below a single card, although the displayed Fps are higher. This behavior is primarily critical at low frame rates, such as the aforementioned 30 Fps. The less Fps, the greater the possible intervals between them and a regular distribution gets even more important.

Solutions?
Reliable solutions do not yet exist, but AMD and Nvidia are informed. The problem probably stems from the methods used on the allocation of computing work on multiple GPUs. With Alternate frame rendering (AFR), the first GPU calculates the first frame while the other calculates the second one and so on. Apparently a tool is lacking to provide these frames with the appropriate harmony so that they are displayed regularly. Upcoming graphics driver could provide the necessary balancing.

Hmm... i was often tempted to get Crossfire, especially with the new 3870X2 card, but held it off till today. I don't regret it. Still sitting on my saved money for the convincing best solution. I'll only go Crossfire or X-fire when it gives a better result than a single card in all available games. and i mean the subjective result, the experience, feeling of the game running completely smoothly, during gaming. Not just the clinically measured fps.

[BTOG46]

I feel exactly the same way about it, I don't mind dropping a few fps for a smoother and more immersive experience in a game.
Plus, a lot of games can give problems with dual cards, and as often the only way to fix things is to disable one of the cards, it makes spending the money on a SLI or Crossfire seem questionable.
But hey, think of the bragging rights twin or even triple cards give you.

[Blín D'ñero]

Crossfire/SLI have always been a choice, next to single. It used to take not very long before a single card came outperforming the dual gpu system.

But this time it is different, said AMD/ATI: X-fire is the way to go. What bothers me is that they release a card (that should prove that gracefully convincing) later than promised ( i can live with that, a patient guy) but before the drivers MAKE it the best solution on Earth. I mean: there is this 3870X2, and i don't have a reason to buy it yet.

[BTOG46]

3870X2

I've already had to deal with someone having problems with this card in the Ubi Settlers 6 forum.

The game isn't happy with SLI or Crossfire, and gives graphical glitches, the normal solution is to disable one card, and now it seems the 3870X2 has the same problem, but not being familiar with the new ATI card, I can't really think of a way round this that doesn't involve losing the benefits of a high end card.

[Blín D'ñero]

But it's not high-end; it's a dual mid-end card. And the best performer in a small list of games. For games that don't like it, he/she should disable crossfire (on the fly, in CCC), that's the workaround and should give at least the single 3870 performance (hopefully, because in some games it is even less than a normal single card )...
And pray that a future Catalyst includes a fix. Sad but true.



Source

Complete review starts here

[BTOG46]

The control centre can disable one of the GPU's as if it were two separate cards on Crossfire?
I hadn't realised that, I told you I was unfamiliar with this card.

[Blín D'ñero]

Yes, i have a screenshot of that somewhere, hang on....

[EDIT]..haven't found it yet.... Anyway, i seem to remember that ticking Catalyst A.I. off also disables crossfire...


Btw: learned that if one has this option in the BIOS:
Advanced -> Chipset -> North Bridge -> PEG Link Mode. Should stay on "Auto".

[Blín D'ñero]

Ahh.. this comes close and should work as well i suppose:

4 seperate GPUs (of course this is X-fire / two 3870x2's so Vista, but in XP/ one 3870X2 you should have 2 seperate gpu's) listed in Control Panel > Device Manager. I'd say: right-click one of the two gpu's to shut it off and crossfire should stop working... hence single card.

[Cobsy]

Print screen button for the win? or was it not your picture :p

[BTOG46]

hmm, do I detect a hint of sarcasm flavour spam.