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 2900xt

[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?.

[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.