Crossfire/sli question

[Dave0w]

To run 2 GFX cards in Crossfire/sli do they have to be the same card.
Ex: can you run a GTX 460 with a GTX 480

 

[Rroff]

Simplest answer yes you need 2 cards of the same model.

More complex answer - if they share the same core technology then its often possible to trick it into working but you wouldn't want to - you generally get nasty stutter and other issues from mis-matched cards, or the fastest ones slowed down to the speed of the slower one or all the work from the slower one is rejected.

 

[setter]

Rroff, i believe crossfire can utilise cards from different generations, ie 5850, 5870? im more used to nvidia and sli, on the few times ive used sli, 6800 gt, 7900 gt, 8800 gts 640 and lately 275's, ive always used identical cards. Very seriously considering another 470 gtx as theyre well priced.

 

[Rroff]

Yes crossfire is a bit more flexible in what can be paired - but its not that useful as it will generally gimp one card or other.

 

[setter]

With sli, is it ok mixing cards with different factory overclocks? I have a gigabyte 470 gtx 630 core clock, might add a second at some stage, most reference 470's are 607mhz, i take it that the faster card will downclock to match the slower model in sli, my use of sli has always been with identical cards.

 

[Rroff]

Unfortunatly its a bit varied what happens - usually it will match clock speeds with the card in the slot closest to the CPU. In theory its supposed to match clock speeds with the slowest card but I've seen just about every combination. So best off using something like afterburner to match clockspeeds on the cards.

 

[setter]

Ahh, i see, as ive only used matched cards on my previous nforce 4 and 6 series boards, on x58 i had the two gtx 275's which were identical cards, gotta admit though, the 470 is a nice card, havent clocked it yet, the only difference is a slight drop in performance in bad company 2 compared to the 275's in sli, but as that was running in dx10, now in dx11, may go some way to explain it, still plays smooth enough though.

 

[Rroff]

I'd love to add another 470... but at 1680x1050 (120Hz) I'm struggling to justify it - everything just runs super smooth with a single 470 @ 800MHz.

 

[Orcvader]

For SLi, the card must match. For crossfire, they must be in the same series eg 58** can crossfire with another 58**, but not with the 57** or 48**.
Another thing is with lucid it doesn't matter what cards you use...

 

[Rroff]

From what I've seen doesn't look like lucid is going anywhere much... slow to support games/applications and so far fairly limited number of supported games coupled with numerous compositing issues and the odd stability issue.

 

[setter]

Yep, gotta get round to clocking mine, i game at 1920x1200 on a rather old benq fp241w 60hz lcd, tbh its a great screen, used for blu ray as well as games, ill probably buy another 470 second hand in a few months time, they do run a bit hot though.