SLI and Cross Fire

I'm aware that there were topics on the old forums about this but I never took the time to read them since I wasn't considering multiple GPUs.

So what exactly are the Pros and cons of Nvidia SLI and and ATI Crossfire?
How much do they improve performance graphics wise?
How about crunching wise?
For crunching is it better to use this feature or individually?
How will boinc see the cards if you run this feature?

Also taking the fact I do some gaming on Cassandra would it be better to use separate cards or to join them?

This one is simple...

For gaming SLI/Crossfire is the way to go, for crunching there is an overhead and you will get slightly less done when in crossfire/sli mode. For me the simple answer is on my gaming box my cards stay in crossfire mode and crunch when I am not gaming and take the small cobble hit. On my standalone crunching boxes I leave the cards as singles. BOINC sees each card as a single regardless of SLI/Crossfire configuration.

+1 to #2...

The only caveat is that if you are are running two 5970s in the same box without a super high-end motherboard, you HAVE to run Crossfire to get them to work at all. Learned this one the hard way...

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Originally Posted by Maxwell

+1 to #2...

The only caveat is that if you are are running two 5970s in the same box without a super high-end motherboard, you HAVE to run Crossfire to get them to work at all. Learned this one the hard way...

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Why was that?

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Originally Posted by Aux10

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Originally Posted by Maxwell

+1 to #2...

The only caveat is that if you are are running two 5970s in the same box without a super high-end motherboard, you HAVE to run Crossfire to get them to work at all. Learned this one the hard way...

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Why was that?

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I have a theory about this since my discussion with Maxwell on this topic... Keep in mind it's only a theory.

From what I have read my understanding is that the 5970 is basically two processors on one card; my first theory is that when running (2) 5970 on one board that his may confuse (for lack of a better term) the CPU into thinking that there are 4 cards running in only (2) slots and it doesn't know what to do with what appears to be redundant information.

The second theory is that on many low end motherboards, eventhough they have 2 or more PCI-E slots on them, not all of the slots run at the same speed they may be operating in x16, x8, x4 or x1 modes.

Now this all may make complete sense except for one thing... I just made all of that up. Sounded pretty good though, right? :-?

I made it all up except the last part and half of the first part. ;)



Seriously though... I don't know what kind of motherboard that Maxwell has but it may have something to do with the PCI-E modes. I bought a MSI 890FXA-GD70 and if you look at the specs eventhough it has (5) PCI Express 2.0 x16 slots, they run in different modes: (2) x16, (2) x8, (1) x4.

I was looking for a new motherboard for my two 4850's when I noticed this issue.

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Originally Posted by STMahlberg

I bought a MSI 890FXA-GD70 and if you look at the specs eventhough it has (5) PCI Express 2.0 x16 slots, they run in different modes: (2) x16, (2) x8, (1) x4.

I was looking for a new motherboard for my two 4850's when I noticed this issue.

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Off topic: I have the P55-GD65, I can personally attest that the MSI GD series is a good quality product line. (Please note, I'm a scaredy cat so I don't oc my boards.)

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Originally Posted by Aux10

Off topic: I have the P55-GD65, I can personally attest that the MSI GD series is a good quality product line. (Please note, I'm a scaredy cat so I don't oc my boards.)

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I've owned a couple of MSI boards and have been pleased overall. I'm with you on OC; I was nervous as heck seeing what my AMD 955 could do, I got it from 3.2 to 3.7 before it crashed but I used AMD's OC utility which takes it in real small steps.

I run it at it's normal speed though, I can't afford to loose this system before I have a backup since I use my rig for work too. Now once I have The Annihilatrix running, I might get a little more daring. :)

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Originally Posted by Maxwell

+1 to #2...

The only caveat is that if you are are running two 5970s in the same box without a super high-end motherboard, you HAVE to run Crossfire to get them to work at all. Learned this one the hard way...

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Originally Posted by Aux10

Why was that?

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Originally Posted by STMahlberg

I have a theory about this since my discussion with Maxwell on this topic...

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The truth: Gremlins, Hobgoblins and creepy crawly things...... >:) >:) >:)

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Originally Posted by Fire$torm

The truth: Gremlins, Hobgoblins and creepy crawly things...... >:) >:) >:)

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lol

So any ways how big of a hit will I get for using SLI?

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Originally Posted by Aux10

So any ways how big of a hit will I get for using SLI?

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It shouldn't be much. If you want, to, by all means use it.