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I am setting up my first crossfire rig and after reading a bit I figured I'd just ask.  I use poclbm and I see I can use device=0 and device=1 to run 2 instances now do I use the same worker or do I have to have 2 different workers setup for each video card.

I'm sure it sounds like a dumb question but just wanted to ask.

from what i understand, crossfire lowers hashrate a bit, but you dont have to buy stuff to make Dummy plugs

i have not mined with crossfire , because i do not now how to either

actually, i think i tried to mine crossfire, for like a couple of hours till i bought some material for dummy plugs

i could only get 1 video card to work

it wuold just keep saying, error error something error for the second card

but i figured out something, i think you have to FAKE a monitor anyway, or Attach a secondary/third/fourth on desktop properties, and extend it, just make sure you dont drag icons and stuff to the "Second" "third" and "Fourth" screen

I don't recommend Crossfire; it significantly decreased my mining performance. It's not hard to get both cards to work separately, though. If your monitor has two input ports (many do), just plug the second card into the monitor's second port. If not, do this (http://blog.zorinaq.com/?e=11).

To answer your question, though, I'm pretty sure you still have to set up two workers, one for each device. Just try yourself and figure out what works.

You make two different miners, one for each GPu.

Crossfire made 0 difference for me in terms of performance, as a datapoint contrary to the two guys above me.

I also run two 5770's in crossfire mode - and get about 180 Mhash/s from each. I was getting the same when i had only one, so I don't think crossfire is hurting anything.

I have one batch file that starts each GPU on two separate lines with the same text for each, only difference being one has device=0 and the other has device=1 (sorry I don't have the file right now or I'd give the full text). I then get two 'DOS' windows, one for each GPU.

Hope that helps...

That does help, you use 2 workers or just 1?  I would assume 2 workers but want to make sure.

Crossfire is only need for a setup in excess of 2 PCIe cards on a Windows bassed machine to run without a 3rd or 4th monitor. You could use a dummy dongle to get around this if you do not want to use crossfire and you have 3 or more cards.

In linux, you do not need crossfire or DummyVGA

Thanks for the info.. I'm going to order another on or two 5770s for mining. Could get 5830s but this way I can crossfire for gaming :)
I get 203MH/s with my current card, as reference.

Are you sure? Any proof please?

There's a ton of references on the forum for this.

I, for one, welcome our non-dummy plug requiring Linux overlords.

Additionally, if you happen to NVIDIA hardware already (worse hashrate than ATI, but *if you already have it*) you don't need to go above run level 3 - a welcome power saving.

Quick question already posted in previous posts, but not answered:

Do you need two workers when running 2 GPU's?

I have 2 rigs with 2x asus EAH6870 cards in them.  Both are running in crossfire at about ~300MH/sec.
I run 2 miners on each rig, same as if I were not using crossfire.

GPU overclocked to 1010Mhz, mem at 1100,
I know I need to get msi afterburner and fix that, but 300MH/card really isnt too bad