How identical do vid cards have to be to use SLI ?

[Bat123Man]

I have an EVGA 8800 GTS 320 MB video card. My mobo supports SLI (Asus P5N-E) and I already know I will have to purchase a bigger PSU (currently have 380W TruPower 2.0). I have found there seem to be many more EVGA 8800 GTS 640 MB cards on the used market, in fact, I can't find any 320 MB versions in my area. Will almost identical 8800 GTS cards play well together if one is 320 MB and the other is 640 MB in SLI mode? Will the combined total of memory available to games be 960 MBs or will it be limited to 640?

And what if I can't find an EVGA, but go with another brand, but make sure it is an 8800 GTS? Or can I even go with an 8800 GT? I will likely not do this, but am wondering what my options are.

Thanks,
BM.

 

[lavaheadache]

you can only use g80 GTS's. That means either 320 or 640 meg cards. Also the way SLi works is that you will only be using the lowest amount of memory between two cards. So a 640 and a 320 Sli setup will only have 320 megs available to use. Depending on your resolution, level of AA and OS(no DX10 on XP which tends to need higher amounts of vram) you play with this may or may not be of big concern. Either way SLi should benefit most of the time and give good gains. I recommend you try it out only if you get a real good deal on the g80 GTS because $100-$150 could get you almost 2x the power you have now. Even if you decide to just get 1 newer high end card that powersupply is gonna be your achilles heel.

 

[taltamir]

the combined total will be limited to 320MB.. it is always equal to the smallest ram of a single card.

How close they have to be entirely depends on arbitrary driver issues that the manufacturer makes... AFAIK a 320 and a 640MB will work with each other. but a 512MB is based on G92 and will not. For AMD different chip types will allow you to xfire them together, they just will work poorly together if different

But is it really worth it? you can buy a 9800GTX / GTX250 or a HD4850 for about 100$. Much better choice as there is no multi GPU issues, and the performance is a decent amount better, and it doens't take obscene amounts of power.

 

[Bat123Man]

Thanks for the info. Taltamir, that is depressing man! I clearly remember buying the 8800 GTS thinking I could wait a year or two to add a second card in SLI mode, and be set for the foreseeable future. Paid a premium for that thought.... I can find the 250 GTS part for around 200 bucks (I'm in Canada, eh). Do you know if there is a vid card roundup which includes both the 8800 GTS and the 250 (or at least the 9800 GTX+) ? I checked Anand's vid section, but none of his most recent comparisons include the 8800. I need to find some basis for comparison to see if the 250 is worth it, or if I should try to get a matching 8800 GTS for much less (assuming I can even find one).