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Re: [Xen-users] Primary VGA Passthrough Status

If you are after a low end card, you might as well just
buy a genuine Quadro 2000. It's single-slot, powered from
the slot (no auxiliary power required), should be ample
for a HTPC, and will "just work". And they are cheap
enough on ebay that it's not worth trying to cut a

On Tue, 8 Oct 2013 17:49:35 -0700, David Erickson <halcyon1981@xxxxxxxxx> wrote:
David or Gordon have you tried this on lower end cards like a GT
640? (Maybe there isn't a Quadro even close to flash it to). These
cards are major overkill for a non-gaming HTPC.


On Tue, Oct 8, 2013 at 3:22 PM, David TECHER  wrote:

Gordan is right.

In the past patches maintenance for NVIDIA was a real pain. That's the
reason why I stopped to maintain those patches in February, 2013.

1) Soft-moding a GTX 480 to a Quadro 6000 aims at unlocking the
expected feature on the card


I tested on two GTX 480 cards and it works very well. Just a bios to
edit/update. Check the checksum and updates straps bits

2) Hard-moding a GTX 680 to a 1/2 GRID K2 works very well too. I
tested it on a Gigabyte GV-N680OC-2GD...it works like a charm

3) Hard-moding a GTX 670 to a 1/2 GRID K2 works very well too. I
tested it on the MSI N670GTX-PM2D2GD5/OC...it works like a charm (just
a few resistors to remove)


This card has a similar PCB than Asus card provided/tested on the
eevblog forum


  DEÂ: David Erickson
 ÃÂ: Gordan Bobic
 CCÂ: "xen-users@xxxxxxxxxxxxx [7]"
 ENVOYÃ LE : Mardi 8 octobre 2013 20h56
 OBJETÂ: Re: [Xen-users] Primary VGA Passthrough Status

On Tue, Oct 8, 2013 at 9:43 AM, Gordan Bobic  wrote:
 On Tue, 8 Oct 2013 09:20:51 -0700, David Erickson  wrote:
  On Tue, Oct 8, 2013 at 5:42 AM, Gordan Bobic Âwrote:
 ÂOn Tue, 8 Oct 2013 00:04:33 -0700, David Erickson Âwrote:

 Â On Mon, Oct 7, 2013 at 11:29 PM, Gordan Bobic Âwrote:

 ÂOn 10/07/2013 09:33 PM, David Erickson wrote:
 ÂÂ Hi All-
 ÂÂIs it possible yet to pass through a ATI or Nvidia GPU as the
 ÂÂVGA card to a Win 7/8 VM, and have it fully functional there

 ÂÂWhy exactly do you need the card to be primary in domU? IME this
 Âdoesn't gain you anything other than being able to see the BIOS
 Âscreen and boot animation on the external monitor (which in itself
 Âisn't worth the extra effort).

 ÂPrimarily it is for htpc functionality like Blu-ray playback
 Âand Digital Cablecard based playback using devices like a HDHR
 ÂPrime. I believe the code that tests for playready (or
 Âcompatibility always looks at the primary video card and finds it
 Âtotally missing any of these features and refuses to play back
 Âproperly. I need to verify that having a passed through card as
 Âprimary actually solves these issues, but I think it is a
 Âhunch (unless anyone else has already tried this and proved it

 ÂI never used it so cannot comment on it. David Techer maintains a
 Âpatch set for Nvidia cards that include primary passthrough
 ÂThe one in particular you will need is the one that gives the VBIOS
 Âloading supprot in domU. Between that and a GTX480 modified to a
 ÂQuadro 6000 (VBIOS editing required) you _might_ just be able
 Âto get it to work. I never tried primary passthrough since
 Âpassthrough has always worked for all of my requirements.

 Â Â without crashing the guest or the host during operation or when
 ÂÂresetting the guest?

 ÂÂIt works fine with Nvidia Quadro cards (real or modified
 Âprovided your hardware works properly (e.g. no dodgy PCI bridges
 Âas Nvidia NF200) bypassing the IOMMU). The latter is, it turns out,
 Âquite rare - an awful lot of hardware seems to have IOMMU support
 Âbroken to some extent.

 ÂIs there something special in the bios/firmware that is enabled
 Âconverting these to Quadros?

 ÂYou have to modify the strap bits. This can be done with a BIOS
 Âon cards up to GTX480, or with some soldering on a GTX680 (you will
 Âneed good eyes, steady hands, high quality soldering paste and some
 Âpro grade soldering kit (hot air or oven - you might be able to
 Âget away with a really tiny soldering tip, but bear in mind that
 Âyou will be looking at soldering both ends of a resistor that is
 Âlong, without shorting it out). If you want the easy option, go
 Âfor a GTX480 and BIOS mod it (or a GTX470 -> Quadro 5000 or a
 ÂGTS450 (make sure you get a 1GB GDDR5 one) -> Quadro 2000 I have
 Âused all of the above extensively without any issues).

 Thanks Gordon, I probably wasn't clear in my question, but when you
convert it from a standard Geforce => Quadro, what is changing at the
 card level to make it more compatible with PCI Passthrough and Xen?

 GeForce drivers don't implement support for various quirks and
 side-effects of running in a VM. Quadro drivers do. You change the
 PCI ID of the card by modifying the straps. That makes the card get
 detected as a Quadro rather than a GeForce, and the Quadro driver
 deals with the quirkyness and side-effects of running in a VM (e.g.
 the fact that the physical BARs differ from the virtual BARs).

 The hardware between the GeForce and the Quadro is by and large
 the same. The reason for the modification is to convince the Quadro
 driver the card really is a Quadro and that you paid an extra pile
 of cash for the privilege of running it in VGA passthrough.

  Is it some feature of the new firmware that is being flashed to the

 No, it's a hack to facilitate the use a driver that can handle
 in a VM.

  And do Geforce cards just absolutely not work at all prior to
 being converted to Quadros?

 GeForce cards absolutely do not work with VGA passthrough without
 modifications; at least not without an additional, unsupported patch
 set which doesn't work for recent cards (4xx cards work, not sure
 about the more recent ones), recent drivers (more recent than
 and recent OS-es (more recent than XP).

 And unless your time really is worthless, getting a GeForce 4xx
 card and modifying it once with no other side effects is a lot less
effort than maintaining your own build of Xen packages with the extra
 patches, even if they do work for your specific use-case.


Thanks that made it very clear, and I totally agree on the time point.

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