# crossfire & 890fx setup (unsolved)

## hedmo

hi 

this week i found out that my M-board supported IOMMU so i would like to try it on.i can not find 

any info for enable it but disable it.

The thing is that would like to get my 2 x radeon2900xt and crossfire up running without a bridge but the problem is:

Master: 0:0:0 

Slave: 0:0:0 

CrossFire is disabled on current device

CrossFire Diagnostics:

CrossFire can work with P2P mapping through GART

i have manage to understand that i have to setup the p2p mapping through my M-B 890xf(codename:RD890) chip.

i have not manage to find much about this and it left me to the iommu thing.

regards hedmo

mybox:

m4a89dt pro 

AMD Phenom(tm) II X6 1055T Processor

2x ati 2900xtLast edited by hedmo on Thu Jul 21, 2011 11:14 am; edited 2 times in total

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## Mad Merlin

I'm not entirely sure what you're hoping to accomplish here, but to clarify, an IOMMU has nothing to do with SLI/Crossfire. An IOMMU allows one to (among other things) pass through some physical hardware (like PCIe video cards) directly to a VM with minimal overhead. Crossfire of course is just using two video cards together, acting as one virtual (hopefully, faster) video card.

Are you trying to setup Crossfire, or are you trying to use an IOMMU?

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## hedmo

mad merlin wrote:

Are you trying to setup Crossfire, or are you trying to use an IOMMU?

both

to get my gpu cards up running .i have to enable

iommu in the kernel or i get black à black screen.

My m-b have the iommu support.i have set iommu in

kernel,set it in grub and in bios.in dmesg i get 

"set iommu in bios" . about crossfire,as far as i have understand 

you can get 2-4 gpu cards up running in crossfire without 

à bridge via (gart) ,iommu?.

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## hedmo

after a time of searching for the answer to why i cant activate crossfire i found out that only HD48xx and up

support crossfire for linux.

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