How much does performance drop by when using more than 1 graphics card?

[TGJJ]

I was thinking of setting up my own mining rig using 3 graphics cards. How much should I expect the performance of each card to drop by when using them together? Thanks!

[runlinux]

There is virtually no performance drop.

I have 4 cards i a single rig and no drop that I can see.

[gochk]

It doesn't ... I have 3 cards in 1 machine - added over time. It generates more heat; but, I haven't seen any drop in performance.

But, since you are a newbie, I hope you are not buying those cards for mining purposes. I don't know where the product is at (haven't been following it), but, there's suppose to be a product out that'll blow GPU mining off. Search BFL on this forum ... or go to  http://www.butterflylabs.com/products/

[Vladimir]

I recall having 8xGPU boxes and each of them were performing at 100% capacity. Though in practice sometimes it makes sense to overclock GPU's a lil bit less when there are many of them for a given power and cooling scheme.

[TGJJ]

It doesn't ... I have 3 cards in 1 machine - added over time. It generates more heat; but, I haven't seen any drop in performance.

But, since you are a newbie, I hope you are not buying those cards for mining purposes. I don't know where the product is at (haven't been following it), but, there's suppose to be a product out that'll blow GPU mining off. Search BFL on this forum ... or go to  http://www.butterflylabs.com/products/

When is the release date, and those numbers seem a bit good to be true? Also would it not be possible to earn back the cost of the machine in the time before release? Any advice would be greatly appreciated.