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SLI conflicting with different amounts of graphics memory?

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  • Graphics Cards
  • Memory
  • SLI
  • Graphics
Last response: in Graphics & Displays
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May 9, 2010 5:58:54 PM

Hey all, i just bought an msi twin frozr GTS250 off of new egg,. there are two versions, one with 512meg memory and the other with 1gig. other than that, the specs are the same. i bought the 512meg version since it was a steal with the rebate that was offered, but later i might want to get another and SLI them. since its basically the same card but with different amounds of ram, if i want to SLI would i have to get another 512meg version? or could i get the 1gig card and sli it with the 512meg since its pretty much the same

thanks all, i still have a lot to learn haha

More about : sli conflicting amounts graphics memory

May 9, 2010 6:48:56 PM

You can SLI them. Though you will only be using one cards memory.
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a b U Graphics card
May 9, 2010 6:53:43 PM

when you do, make sure the one with more memory is in the primary PCI-E slot so you can use the one with more memory.
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May 9, 2010 11:17:21 PM

oh so when you SLI two cards, it uses the graphics processing power of both, but only the memory of the first?
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a c 88 U Graphics card
May 10, 2010 12:03:22 AM

nope... it only uses as much memory as the smaller one has on both cards. so if you sli 512m with 1g, it will only use 512m on both cards, the extra 512 on the 1g card will be 'wasted' and not used
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a b U Graphics card
May 10, 2010 12:07:56 AM

Read lower post...
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a c 88 U Graphics card
May 10, 2010 12:14:15 AM

lol wut?

so where does the secondary card store all the data if not in the memory on the board? SLI link isnt wide enough to transfer enough data fast enough from the primary cards memory to the secondarys gpu??
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a b U Graphics card
a b } Memory
May 10, 2010 12:19:12 AM

AMW1011 said:
No, it will use whatever memory the primary card has. If the primary card has 2GB of memory, and the secondary has 1Gb then ti will use the 2GB. It doesn't matter what amount of memory, or even if the memory works, on the secondary card because it is completely unused. Only the primary card's memory matters. You are getting it confused with clock speeds and shaders.


it can't do this as both cards nee to use their own memory to create frames in sli, it reverts to the smaller size since the secondary card can't access the extra memory of the primary to make up for lost memory (not to mention it couldn't use the other cards memory since that card would need it for itself)
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May 10, 2010 12:23:05 AM

Wow, your right that sounded way off.

What I meant was that in SLI and Crossfire, each frame is rendered by the separate GPU. So the frame rendered on the GPU1 will have 2GB to use while the secondary will have 1GB to use. This will only be throttled when it creates irregular speeds. This is because the primary GPU has more to store on it's memory than the secondary. So the 2GB on the primary card will have an advantage, at least this is how I know it.
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a b U Graphics card
May 10, 2010 12:28:35 AM

Nope they are right:

Quote:
Can I mix and match graphics cards with different sizes of memory?
When purchasing a second graphics card, you should try to match the memory size so that you are ensured full value and performance from your purchase. However, while it is not recommended, NVIDIA does offer the flexibility to run graphics cards with different sized memory by using CoolBits. Using CoolBits (value set to 18), you can force both of the cards to use the lower of the two memory sizes and operate them together in SLI mode. When dissimilar memory sizes are enabled to work together using CoolBits, the effective memory size for each card becomes the smaller of the memory sizes. Instructions to enable this feature can be found here.


http://www.slizone.com/page/slizone_faq.html#c19

I was under the impression that since there is more load on the primary card's memory that it would have an extra 1GB to use for that while the rest is used for the same rendering as the secondary, guess not.
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May 10, 2010 12:28:36 AM

mindless728 said:
i wouldn't think they would do this just because when the game starts using more than 1GB vram (im using your example of 2GB + 1GB) the card with 1GB might make its frame way too late (after the 2GB card) making it pretty much useless. So it would make sense to just limit the amount of vram to the lowest common card


Right this would cause horrible micro stuttering, but the primary card has to store more information than the secondary card, which is what causes what people call microstuttering now, I thought extra memory on the primary card would alleviate that a bit, but I guess not.
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a b U Graphics card
a b } Memory
May 10, 2010 12:28:57 AM

AMW1011 said:
Wow, your right that sounded way off.

What I meant was that in SLI and Crossfire, each frame is rendered by the separate GPU. So the frame rendered on the GPU1 will have 2GB to use while the secondary will have 1GB to use. This will only be throttled when it creates irregular speeds. This is because the primary GPU has more to store on it's memory than the secondary. So the 2GB on the primary card will have an advantage, at least this is how I know it.


i wouldn't think they would do this just because when the game starts using more than 1GB vram (im using your example of 2GB + 1GB) the card with 1GB might make its frame way too late (after the 2GB card) making it pretty much useless. So it would make sense to just limit the amount of vram to the lowest common card
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a b U Graphics card
a b } Memory
May 10, 2010 12:32:54 AM

AMW1011 said:
Right this would cause horrible micro stuttering, but the primary card has to store more information than the secondary card, which is what causes what people call microstuttering now, I thought extra memory on the primary card would alleviate that a bit, but I guess not.


i don't see why you would need all that much memory for sli for the primary card, just enough for the frame, just a little under 8MiB (1920x1080x32bit)
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a b U Graphics card
May 10, 2010 12:40:59 AM

An extra 1GB would be complete overkill, but it would make for slightly smoother gameplay. I guess keeping out the rendering path from the rest of the memory would be a coders nightmare, now that I think of it.
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May 10, 2010 12:50:59 AM

so i should just get another 512mb version for sli-ing later then is what ive gotten from all this :p  thanks guys
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a c 273 U Graphics card
May 10, 2010 3:33:35 AM

AMW1011 said:
Right this would cause horrible micro stuttering, but the primary card has to store more information than the secondary card, which is what causes what people call microstuttering now, I thought extra memory on the primary card would alleviate that a bit, but I guess not.

IMHO micro stuttering is down to lack of cache on the CPU.
samwelaye said:
so i should just get another 512mb version for sli-ing later then is what ive gotten from all this :p  thanks guys


To be on the safe side yes, the reason I say that is because the GTS250 is the 9800GTX+ and a 1GB GTS250 cannot be SLi'd with a 512MB 9800GTX+ but it will SLi with a 1GB 9800GTX+.
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May 10, 2010 3:42:02 AM

Back when the micro-stuttering scare was in full swing I was debating whether or not to get 2 8800 GTS 512mb or an 8800 Ultra. I did a good deal of research and I found that there were a few things that contributed to it and that it really wasn't a big deal in the end, which I now know to be true.

MM, can you post a link that supports that? I've never seen the cache blamed, but that doesn't mean it isn't true.
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May 10, 2010 3:47:07 AM

AMW1011 said:
Back when the micro-stuttering scare was in full swing I was debating whether or not to get 2 8800 GTS 512mb or an 8800 Ultra. I did a good deal of research and I found that there were a few things that contributed to it and that it really wasn't a big deal in the end, which I now know to be true.

MM, can you post a link that supports that? I've never seen the cache blamed, but that doesn't mean it isn't true.

I've come to that conclusion after seeing so many posts and articles over the years where it has cropped up and the common denominator has always been a crap CPU or a CPU with very little onboard cache.
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May 10, 2010 3:49:30 AM

too many "best answers" to choose one haha. either way thanks for all the feedback
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