GTX280 and GTX285 SLI?

[palladium]

I have a friend who has a GTX280 but now wants to get a GTX285 for an SLI setup. Is it possible? ( I would think so because they are identical except for the clock speed and fab process, but would want to make sure before I tell him to go ahead with it)

 

[Denithor]

No.

SLI only functions on two identical model cards. You cannot even SLI an 8800GT with a 9800GT even though those cards are physically identical, the BIOS claims they are different so SLI cannot be enabled. And note, if you SLI two cards with different speeds, the faster one will be clocked down to run at the same speed as the lower one (so a stock speed + SSC = both run at stock speed).

If your friend wants SLI he needs another GTX 280 for the second card.

 

[apoppin]

i thought Nvidia was going to allow for some mixing and matching?


technical limitations of SLi or they just want to sell new cards?

 

[aka1nas]

Originally posted by: apoppin
i thought Nvidia was going to allow for some mixing and matching?


technical limitations of SLi or they just want to sell new cards?

Their driver just isn't that smart. It simply looks at the model strings to determine if you have an SLI-capable setup. This is why you can't SLI the 8800GT with the 9800GT or an 8800GTX with an Ultra, even thought the latter two cards only differ by clockspeeds.

 

[apoppin]

Originally posted by: aka1nas

Originally posted by: apoppin
i thought Nvidia was going to allow for some mixing and matching?


technical limitations of SLi or they just want to sell new cards?

Their driver just isn't that smart. It simply looks at the model strings to determine if you have an SLI-capable setup. This is why you can't SLI the 8800GT with the 9800GT or an 8800GTX with an Ultra, even thought the latter two cards only differ by clockspeeds.

let me try again
--it is a *question*

is it a TECHNICAL limitation of SLi .. or will possibly future drivers make for SLi 'mix 'n match' as Crossfire does?

 

[aka1nas]

I'm 99% sure it's completely an artificial driver limitation and if they wanted to they could disable the check and allow you to at least try to SLI any weird combination of cards.

 

[apoppin]

Originally posted by: aka1nas
I'm 99% sure it's completely an artificial driver limitation and if they wanted to they could disable the check and allow you to at least try to SLI any weird combination of cards.

well, what about Focus Group? They should know for sure if it is a driver limitation, at least.
- why i am *asking* is because i remember some talk about it being enabled; then i lost track of it. Didn't Keys plan to do some experimentation with a modest mismatch .. 98XX series, i thought



please do share

 

[Keysplayr]

Well, a 9800GTX 65nm was able to SLI with a 9800GTX+ 55nm. So, it is indeed plausible that a 65nm GTX280 could SLI with a 55nm GTX285 IF the cores are identical and it's just a die shrink. I'll forward the question to Nvidia and get back with an answer.

But you know, even if it did work, I would think the GTX285 would be forced to run at GTX 280 speeds. Therefore, it would just make more sense to SLI a GTX280 with a GTX 280.

 

[aka1nas]

Hi Keys, would you also mind confirming if SLI will force the clockspeeds down to the slower card? Folks around here bring it up all the time, but IME this is not the case and cards with non-identical default clocks will run just fine in SLI at their respective clocks(unless you OC them, of course).

 

[apoppin]

Originally posted by: keysplayr2003
Well, a 9800GTX 65nm was able to SLI with a 9800GTX+ 55nm. So, it is indeed plausible that a 65nm GTX280 could SLI with a 55nm GTX285 IF the cores are identical and it's just a die shrink. I'll forward the question to Nvidia and get back with an answer.

But you know, even if it did work, I would think the GTX285 would be forced to run at GTX 280 speeds. Therefore, it would just make more sense to SLI a GTX280 with a GTX 280.

thank-you for asking for us

for a "normal" person that might make sense - however i want to compare 280 with 285

- what better way?

and i can probably OC my 280 ,,, it does OC

 

[Lonyo]

Originally posted by: keysplayr2003
Well, a 9800GTX 65nm was able to SLI with a 9800GTX+ 55nm. So, it is indeed plausible that a 65nm GTX280 could SLI with a 55nm GTX285 IF the cores are identical and it's just a die shrink. I'll forward the question to Nvidia and get back with an answer.

But you know, even if it did work, I would think the GTX285 would be forced to run at GTX 280 speeds. Therefore, it would just make more sense to SLI a GTX280 with a GTX 280.

You say that, but currently (in the UK at least) there's minimal difference in price between the GTX280 and 285, which means that getting a 285 over a 280 to SLI isn't actually as it might seem.
That may change in the future of 280 prices drop a bit, but currently it's a very real situation that on some sites 285's are cheaper than 280's.

 

[palladium]

Sweet, thanks keys.

If indeed they have to run at identical speeds, I'd just OC the GTX280 to 285 speeds, as what apoppin said. ( 1476 on the GTX280 shaders might be a challenge though - I have my GTX280 run at GTX285 speeds except for the shaders which I set it at 1400.)

 

[Keysplayr]

Originally posted by: Lonyo

Originally posted by: keysplayr2003
Well, a 9800GTX 65nm was able to SLI with a 9800GTX+ 55nm. So, it is indeed plausible that a 65nm GTX280 could SLI with a 55nm GTX285 IF the cores are identical and it's just a die shrink. I'll forward the question to Nvidia and get back with an answer.

But you know, even if it did work, I would think the GTX285 would be forced to run at GTX 280 speeds. Therefore, it would just make more sense to SLI a GTX280 with a GTX 280.

You say that, but currently (in the UK at least) there's minimal difference in price between the GTX280 and 285, which means that getting a 285 over a 280 to SLI isn't actually as it might seem.
That may change in the future of 280 prices drop a bit, but currently it's a very real situation that on some sites 285's are cheaper than 280's.

Of course if the prices are comparable, then I agree. Why not get the 285.
I forwarded a few questions to NV. Just waiting for a reply.

 

[CraigBorthwick]

Hi Guys

I would also like to find out if I can SLI my GTX 280 with a GTX 285.