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#1 2016-09-08 12:48:31

BitterCynic
Member
Registered: 2016-09-06
Posts: 15

[SOLVED] QEMU W3520, Asus P6T, 5770, 7870

I'll just guess at how limited i am with my current hardware and someone correct me if i'm wrong or let me know of a good workaround.

I have an Asus P6T motherboard with a Xeon W3520 CPU, so i have no integrated graphics and three full size PCI-E ports with two of them being x16 electrically while the last one is x4. My current GPU is a Sapphire HD7870 and i have an old XFX HD5770 sitting on a shelf.

I guess most set ups go like this - GPU1 for host and GPU2 for guest OS, roles never being swapped. Alternatively those who have integrated graphics can probably use either GPU when using only host OS? Seen it as a common theme for laptop users who get confused at bad game performance not knowing they're using integrated and not dedicated gpu. Edit: It's called Hybrid graphics on the wiki. Is basic switching possible between two DGPs instead of an IGP and a DGP?

Before i start to set up QEMU i want to know if i can freely swap between the 7870 and the 5770 on the host OS. They're both AMD cards but from different generations probably using different drivers - problematic?
On the guest windows OS I'd always use the 7870 but that's only when i need windows, the rest of the time i could just run linux and ideally i'd want the option to use either one of the GPUs for it. Does that mean a driver reinstall and reboot every time i want to change the gpu i use on linux?

The arch install i have right now was done with the 7870, so if the linux host is going to be limited to a single GPU it has to be the 5770 which means some hardware stuff needs to be done before i begin setting up QEMU.

Last edited by BitterCynic (2016-09-16 09:20:20)

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#2 2016-09-08 22:15:23

BitterCynic
Member
Registered: 2016-09-06
Posts: 15

Re: [SOLVED] QEMU W3520, Asus P6T, 5770, 7870

Plugged in the 5770 in the first slot while moving the 7870 to the second slot. Arch automatically used the first slot one and no problems so far. I have my second monitor connected to the 7870 and it's been sitting in stand-by the whole time, not sure how to use both of them for arch. I guess it's impossible to simultaneously use two dissimilar PCI-E gpus on the same OS? For some reason i think i read it somewhere once that while only one of the gpus will ever actually do any work the secondary one could still be used to simply pass through a video signal through its ports. Edit: It is possible and on arch too but probably yet more headaches for me while editing config files. Relevant old post.

Both screens do have unused d-sub ports though there are none of those on either GPU, i might have a DVI to D-Sub cable somewhere...

Last edited by BitterCynic (2016-09-08 22:38:02)

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#3 2016-09-16 09:18:47

BitterCynic
Member
Registered: 2016-09-06
Posts: 15

Re: [SOLVED] QEMU W3520, Asus P6T, 5770, 7870

Massive waste of time. Turns out both my motherboard and cpu lack "Virtualization Technology for Directed I/O (VT-d)" support preventing me from achieving that near native gpu performance in a virtualised windows guest.

Source: https://wiki.xen.org/wiki/VTd_HowTo
"For ASUS Desktop Boards, these have VT-d support enabled, but Asus does NOT support Linux, so you are on your own with any Linux or Xen issues like broken BIOSes:
[..]ASUS P6T documentation claims support, but does not work due to DMAR-table issue."
and the cpu: http://ark.intel.com/search/advanced?s= … e&VTD=true
W3520 not listed since it only has VT-x

So i'm stuck with no solution until i can afford a hardware upgrade.

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