Crossfire/SLI Questions

When you are running 2 cards in crossfire or SLI, what has to be common of both cards? (e.g. both have to be invidia or AMD based cards)

I have an HIS HD 7850 2GB and with a PSU and motherboard that will allow another card so i was wondering if i was to get another card, what would be a good choice? Should i get a 1GB overclocked card as an additional card doesnt share it memory and only acts as a speed boost?

Help please!

With SLI the cards have to use the same chip and be of the same speed I believe.

With AMD they have to be of the same series. eg a 7850 can be paired with either another 7850 or a 7870.

However the one exception is the 7870xt which can not be paired with 78xx series but instead the 79xx series as it is a tahiti chip instead

The cards work together in tandem and will adjust to mirror the slower of the two. (as it is the fastest the slowest can go derp)

So a 2GB card running with a 1GB card would limit the usable GPU memory to only 1GB. 

Crossfire and SLI get best performance with identical cards, however AMD allows for much more compatibilty than Nvidia

The reason they need identical memory quantities is due to that both GPUs need to load all the shaders and textres etc. that it will be computing.



If the 7850 model as it matches the current one you have based off what you have already said you have

As a common rule of thumb the same card.

This way the GPU and the Memory etc is the same