SLI Difference in RAM

Oompa

Limp Gawd
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Apr 23, 2006
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If I had 2 8600GTSes, but 1 had 512MB and the other had 256MB, could I still use SLI?
 

Dan_D

Extremely [H]
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Feb 9, 2002
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59,176
If I had 2 8600GTSes, but 1 had 512MB and the other had 256MB, could I still use SLI?

I don't think so but even if it did work you'd be limiting yourself to a single 256MB frame buffer doubled on each card. In other words you'd only have the smaller memory amount available. So the 512MB card would only use 256MB of RAM also.
 

cereal_killer24

Limp Gawd
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Nov 26, 2005
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I remember back in the day some one had sli 320mb gts and 640mb gts. I believe they modded the 640mb gts bios to 320mb in order for the sli to run. As Dan said, you would limiting yourself with the 256mb of ram.



 

Oompa

Limp Gawd
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Apr 23, 2006
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I don't think so but even if it did work you'd be limiting yourself to a single 256MB frame buffer doubled on each card. In other words you'd only have the smaller memory amount available. So the 512MB card would only use 256MB of RAM also.
Hm, alright thanks. I was hoping that that it would just drop the 512MB card to 256 but it would still work. Guess I'll be stuck with this single 8600GTS 512mb.
I remember back in the day some one had sli 320mb gts and 640mb gts. I believe they modded the 640mb gts bios to 320mb in order for the sli to run. As Dan said, you would limiting yourself with the 256mb of ram.



How could I modify the BIOS?
 

Betrayer00GT

Limp Gawd
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Feb 25, 2007
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350
Yes, you could.

You would end up running, effectively, with a pair of 256MB 8600GTS cards when in SLI.

This is the same issue that was run into when the 8800GTS 320 and 640 were the two cheapest DX10 cards. You can mix different RAM amounts, and different clock speeds, but which ever is smaller/slower is what the larger/faster card is adjusted to (automatically, by the drivers) when SLI is enabled. You only run into problems when the drivers are not aware that the only differences are clock speed and/or amount of ram. Like an 8800Ultra may still be considered a "different card" by the drivers vs an 8800GTX, even though you could flash one with the other's BIOS and potentially get SLI to work that way.

So, it seems to me, you can have 32SPs running with 512MB of ram for the frame and Z buffers, as well as for textures, or you can have 64SPs total in SLI and 256MB of ram for the frame and Z buffers as well as for textures. I think there are many games that would do better with less RAM available, but more SPs (at least at 32 vs 64), even when they are combined with the inefficiencies of SLI. It will depend on your exact circumstances though, of course.

But, why not just experiment? Good luck!
 

Oompa

Limp Gawd
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Apr 23, 2006
Messages
376
Yes, you could.

You would end up running, effectively, with a pair of 256MB 8600GTS cards when in SLI.

This is the same issue that was run into when the 8800GTS 320 and 640 were the two cheapest DX10 cards. You can mix different RAM amounts, and different clock speeds, but which ever is smaller/slower is what the larger/faster card is adjusted to (automatically, by the drivers) when SLI is enabled.

So, you can have 32SPs running with 512MB of ram for the frame and Z buffers and for textures, or you can have 64SPs total in SLI and 256MB of ram for the frame and Z buffers as well as for textures. I think there are many games that would do better with less RAM available, but more SPs, even when they are combined with the inefficiencies of SLI.

But, why not just experiment? Good luck!
This is great news. I had 7900GT 256mb SLI, but one card died and I had it RMAd, since they were different vendors I ended up with a single 7900GT 256MB and a 8600GTS 512MB. My friend has a spare 8600GTS 256MB that he'd be fine with trading (just going into a kids machine), so I wanted to make sure it'd work before having to pester him. The 7900GT 256MB SLI performed noticeably better, so even if the cards are still limited to 256MB, I'm sure they'll do better than my single 8600GTS with 512MB.
 

MrGuvernment

Fully [H]
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Aug 3, 2004
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20,309
i think you could, but it could only use 256mb


why bother? it isnt worth it, unless you already own both cards, otherwise sell one and get a 9600 or something
 

Betrayer00GT

Limp Gawd
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Feb 25, 2007
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This is great news. I had 7900GT 256mb SLI, but one card died and I had it RMAd, since they were different vendors I ended up with a single 7900GT 256MB and a 8600GTS 512MB. My friend has a spare 8600GTS 256MB that he'd be fine with trading (just going into a kids machine), so I wanted to make sure it'd work before having to pester him. The 7900GT 256MB SLI performed noticeably better, so even if the cards are still limited to 256MB, I'm sure they'll do better than my single 8600GTS with 512MB.

Ahh, then I would definitely "pester him". Try it. Worst case is you could just "pester him" again to put it back (if he even cares, which he might not - right?).

Your 8600 series cards are a bit different than the other stuff out, now. Only 32SPs was a really limiting factor for them. Way more so than 256MB vs 512MB, IMO. There is only now a 64SP card out, the 9600GT. That took way too long, and people like you suffered since all there was (most likely) when you bought yours was 32SPs w/512MB ram or 96SPs with 320MB of ram for ~50% more $. Too much of a jump, in SPs and cost, one to the other - that's for sure.

Bad Nvidia!

Anyway, try it. Plus, let us know how it goes!
 

Oompa

Limp Gawd
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Apr 23, 2006
Messages
376
So I got the 8600GTS today. It's been awhile, but it finally rolled around. I've connected them both, and they both are working fine, but SLI won't pop up. GPU-z says that SLI is available, but I can't find the option in the nVidia settings, and the little balloon that should pop up didn't. I've tried putting the 512mb card as both the master and the slave card, both have accomplished the same thing. Am I out of luck or am I missing something?
 
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