SLI GDDR3 + DDR3?

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makaseo

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Sep 17, 2012
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Hi guys, stumbled across this forum while looking for an answer to my question and thought you guys could help!

My friend currently has a EVGA 9800GT, 512MB of DDR3 with an SLI bridge connector.

He's looking to upgrade his performance a bit and found another 9800 GT for quite cheap, but it's an MSI variant with 768MB and isn't sure if it's DDR3 or GDDR3. For some reason, I'm having a hard time finding specs for any card like that online, only 1GB and 512MB models.

From what I've read on the forums, as long as the memory is 256-bit like his current one, clock speeds should set themselves to the lower card, and the memory as well, and he's not really concerned with that.

My question is, would a DDR3 card SLI properly with a GDDR3 card?

Hope I have enough info. Thanks for any replies!
 
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From the Nvidia SLI FAQ:
Can I mix and match graphics cards from different manufacturers?

Using 180 or later graphics drivers, NVIDIA graphics cards from different manufacturers can be used together in an SLI configuration. For example, a GeForce XXXGT from manufacturer ABC can be matched with a GeForce XXXGT from manufacturer XYZ.

Can I mix and match graphics cards if one of them is overclocked by the manufacturer?

Yes. A GeForce XXXX GTX that is overclocked can be mixed with a standard clocked GeForce XXXX GTX.

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...
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Deemo13

Deemo13

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Jul 18, 2011
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That's actually a very good question. I'm about 99% certain they are the same and would operate just fine. I would still try to find a 512MB version anyway to ensure compatibility. For example:

My GTX460 1GB will not SLI with the 768MB version because the 1GB variant has 256-bit memory and the 768MB has 192-bit.

9800GT's were not made like this though, as all of them came with a 256-bit bus.

I am coming to the conclusion that DDR3 and GDDR3 in terms of graphics cards are the same.
 
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makaseo

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Sep 17, 2012
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Thanks Deemo13--Yeah, I've read somewhere that DDR3 and GDDR3 are the same thing that manufacturers just refer to differently for marketing reasons or something like that, but I didn't know whether to believe that or not.
 
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Mousemonkey

Mousemonkey

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Sep 3, 2006
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A 768MB 9800GT? That don't sound right to me.
 
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GreenDutchAlien

GreenDutchAlien

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bystander

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From the Nvidia SLI FAQ:
Can I mix and match graphics cards from different manufacturers?

Using 180 or later graphics drivers, NVIDIA graphics cards from different manufacturers can be used together in an SLI configuration. For example, a GeForce XXXGT from manufacturer ABC can be matched with a GeForce XXXGT from manufacturer XYZ.

Can I mix and match graphics cards if one of them is overclocked by the manufacturer?

Yes. A GeForce XXXX GTX that is overclocked can be mixed with a standard clocked GeForce XXXX GTX.

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.
Click to expand...

So, with the use of Coolbits, you can use two different memory sizes and still SLI them.

DDR3 and GDDR3 are the same thing, just a different way of labeling the memory. However, if the cards are different like the 460 SE compared to the original 460, they wouldn't SLI together.
 
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GreenDutchAlien

GreenDutchAlien

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Guess i'm too shy to go in against the "not recommended" advice from Tom's, shame though why they don't state why not. You know why ?
 
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bystander

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That was directly from Nvidia, not Tom's, and they said why not. "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."

They are just saying that you are not getting full value from the card with higher memory, as it gets used as if it has the same amount as the lower end card.
 
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Mousemonkey

Mousemonkey

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Sep 3, 2006
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I hadn't heard or read about a 9800GSO either but it wouldn't surprise me in the slightest if there was such a thing floating about, just because I don't know about does not mean it doesn't exist.
 
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makaseo

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Sep 17, 2012
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Thanks for all of your replies!

Update: He got the card, the seller listed it wrong. Turns out it's a 1GB card, not 768MB. That explains why I couldn't find it online.

I helped him install it and now both cards are detected by the system in Nvidia control panel and we used the SLI bridge that came with his EVGA card, but the SLI option isn't showing up in the control panel, only the option to use one of the cards as a dedicated PhysX card.

Is it because of the different memory after all? Both of them have 256-bit memory bus, 112 CUDA cores, the new one has a slightly higher core clock (660 vs 600) and larger memory size, same memory clock. Pretty sure the SLI bridge is quite snug as far as connection goes...

EDIT: Just read the reply about CoolBits. Is that the only way to SLI two cards with different memory sizes? If so, would you guys recommend it? I'm a bit hesitant to recommend something called "ForceWare" to my friend. Another forums seems to suggest that CoolBits is pretty old, and newer drivers should scale down the memory usage of the larger card automatically.
 
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makaseo

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Sep 17, 2012
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Okay, followed some instructions on how to enable CoolBits in the Nvidia Control Panel, did a reboot, and it worked! Didn't think it would just be a dead simple registry edit. The SLI option showed up, and he's happily playing Guild Wars 2 at close to twice the framerate he had before. Thanks so much for the help, guys. Really appreciate it.
 
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