Xen dom0 with Nvidia proprietary driver

[powerhouse]

My ultimate goal is get a Xen hypervisor installation running LMDE 12 as dom0, and Windows 7 as domU with VGA passthrough.

I have a PNY Quadro 600 graphics card and like to get the Nvidia proprietary driver to run on the Xen kernel, so I can have full graphics support under the dom0 LMDE kernel.

Can I just install the Nvidia proprietary package when running the Xen kernel? Has anybody done that before?

My understanding is that the Nvidia proprietary driver requires a modified kernel. Will that work together with the Xen kernel?

Thanks!

[powerhouse]

I've finally been able to try it out. The proprietary Nvidia driver installs onto a Xen dom0 but then won't boot. I haven't played around with it much as I guess I won't need the driver after all. I'm planning to run Win 7 on a domU with VGA passthrough and since I have only one monitor and graphics card I will have to access my dom0 via ssh X terminal from within Windows, in which case the Nividia driver is unnecessary.

[powerhouse]

I've added a second graphics adapter to my system, this time a cheap AMD (ATI) 6450 card in the first PCIe 16 slot. It was recognized immediately after reboot (I had an Nvidia card in that slot) and booted right into the Linux Mint desktop (I'm now using Linux Mint 13 Mate). The AMD proprietary driver also installed without a problem.

Now I have my AMD card running in a Linux Mint dom0 on top of the Xen hypervisor, using the proprietary graphics driver.

Conclusion: The AMD proprietary driver seems to work better than the Nvidia proprietary driver when installed on a Xen dom0.

[GizmoChicken]

@powerhouse: Thanks so much for posting your findings. I've been pulling my hair out trying to get Nvidia proprietary drivers to work with Ubuntu 12.04 as dom0 under the Xen 4.1 hypervisor. Good to know I'm not the only one having trouble with Nvidia. I'll follow your lead and will try a Radeon 6450 card and drivers. Just wish that I had read your post before buying my new Nvidia GT 610!

Oh, I wrote to Nvidia to report that, when running Ubuntu 12.04 as dom0 under the Xen 4.1 hypervisor, my GT 610 isn't able to display anything requiring Xorg. In response, I was told that "GPU passthrough requires Xenserver 6 and a supported graphics card and unfortunately your GT 610 is not supported," which of course has nothing to do with displaying video on dom0.

Maybe if Nvidia gets a few more complaints they'll look into the problem...

http://www.nvidia.com/object/driverqual ... rance.html

[powerhouse]

Yeah, it seems there is a problem with the Nvidia driver. However, I believe I saw somewhere that it can be made to work with the Xen hypervisor, but I didn't bookmark it as I have now no need for it.

By the way, the AMD 6450 was NOT a replacement for the Nvidia Quadro 600 (or now the Quadro 2000 I have), the former is much too underpowered to do anything but the simplest stuff. So it might be worth to look at a little more graphics power, unless you don't care for desktop effects, games, etc.

For me, I'm not sure I'll keep the 6450 - even youtube video on full screen stutters.

P.S.: I'm writing this within Windows 7 running on a Linux Mint 13 system with Xen hypervisor - bye bye dual-booting !!! Ah, did I say my Windows Experience Index is 7.0 ? And I can switch between both concurrent systems at the press of a button. That's what the Nvidia guys meant saying, but they didn't get your point.

[GizmoChicken]

@powerhouse: Thanks much for the additional information! I'm guessing that you are using GPU passthrough to your Quadro 2000 to get the Windows Experience Index of 7.0 in a Windows VM running as domU. True?

Also, you mention that "even youtube video on full screen stutters" with the AMD 6450 on your dom0. Just curious, does video stutter under native LMDE 12 when not running under the Xen hypervisor?

I ask about your AMD 6450 because youtube video is flawless with my Nvidia GT 610 (which is comparable to the AMD 6450) under native Ubuntu 12.10 (that is, when not running under the Xen hypervisor) using either the Nvidia proprietor driver or the Nouveau driver, which is an open source driver for Nvidia cards. And although the Nvidia proprietary driver doesn't work at all with Ubuntu 12.10 as dom0, the Nouveau driver sort of works for my Nvidia GT 610 with Ubuntu 12.04 as dom0. I say "sort of" because, much like you reported, even youtube video on full screen stutters with the Nouveau driver, which isn't acceptable for my needs. Strangely, video is quite strong on an old laptop (with integrated Intel graphics) both when running native Ubuntu 12.10 and also when running Ubuntu 12.10 as dom0. Something about this doesn't make sense.

I'll add that, at least on my setup with an Nvidia GT 610 and native Ubuntu 12.10 as a host (no Xen), Windows 7 runs extremely well and with reasonably strong video support in VirtualBox (www.virtualbox.org). So if you don't absolutely need Xen, VirtualBox might be a option worth considering. (You would only need a single video card, as GPU passthrough wouldn't be needed for your Windows VM. You might not get a Windows Experience of 7.0 on your Windows VM in VirtualBox, but you might get close to it.)

As for me, my goal is to run a few non-graphical servers as domU virtual machines alongside a graphical dom0 that can at least play youtube videos without stuttering. And since I have no need for a graphical environment on my domU virtual machines, I have no need for graphical passthrough. I could accomplish something similar using Ubuntu 12.10 as a host for VirtualBox, but Xen would be a more stable environment for my virtual servers.

As much as I want to stick with Linux running as dom0 under Xen, I have found that, in view of the video card issues that I'm having with Linux running under Xen, Windows 8 under Hyper-V is currently a better alternative for me: In Windows 8 running as the control domain under Hyper-V, I get a Windows Experience of 5.3 with my current Nvidia GT 610 (not great, but good enough for now) and I get the stability of virtual machines running under Hyper-V, which is a bare-metal hypervisor that is very similar to Xen. Also, although I don't have much reason for a second graphical environment, I can also run Ubuntu 12.10 Desktop as a graphical virtual machine with reasonable video performance.

[powerhouse]

@powerhouse: Thanks much for the additional information! I'm guessing that you are using GPU passthrough to your Quadro 2000 to get the Windows Experience Index of 7.0 in a Windows VM running as domU. True?

Absolutely true!

Also, you mention that "even youtube video on full screen stutters" with the AMD 6450 on your dom0. Just curious, does video stutter under native LMDE 12 when not running under the Xen hypervisor?

I don't believe it's a Xen issue, though I haven't tested it under native Linux Mint. I have the proprietary AMD driver installed and enough CPU power left for the dom0 even when the Windows domU is running. I will try to test it under native Linux later, just to make sure. My guess is that either the 6450 isn't up to the task, or the proprietary driver doesn't do so well. At the moment it doesn't bother me. I may replace it for a little stronger card if needed. In your case, if you want to switch to Xen, you should look at a little more powerful AMD card.

I ask about your AMD 6450 because youtube video is flawless with my Nvidia GT 610 (which is comparable to the AMD 6450) under native Ubuntu 12.10 (that is, when not running under the Xen hypervisor) using either the Nvidia proprietor driver or the Nouveau driver, which is an open source driver for Nvidia cards. And although the Nvidia proprietary driver doesn't work at all with Ubuntu 12.10 as dom0, the Nouveau driver sort of works for my Nvidia GT 610 with Ubuntu 12.04 as dom0. I say "sort of" because, much like you reported, even youtube video on full screen stutters with the Nouveau driver, which isn't acceptable for my needs. Strangely, video is quite strong on an old laptop (with integrated Intel graphics) both when running native Ubuntu 12.10 and also when running Ubuntu 12.10 as dom0. Something about this doesn't make sense.

I think Nvidia cards and drivers are generally performing better - if they work - than similar AMD cards. The nouveau driver isn't up on par with the proprietary Nvidia driver, though. But it's usually enough for most things. I can't remember having problems with the nouveau driver when I was using my Quadro 600 card, under Xen hypervisor. So I really believe it boils down to a slow AMD 6450 card (or Nvidia GT 610 in your case) - it's the most basic entry level card they have.

I'll add that, at least on my setup with an Nvidia GT 610 and native Ubuntu 12.10 as a host (no Xen), Windows 7 runs extremely well and with reasonably strong video support in VirtualBox (www.virtualbox.org). So if you don't absolutely need Xen, VirtualBox might be a option worth considering. (You would only need a single video card, as GPU passthrough wouldn't be needed for your Windows VM. You might not get a Windows Experience of 7.0 on your Windows VM in VirtualBox, but you might get close to it.)

I used VirtualBox with Windows XP for some time on my old PC (Core2 Duo) and like it's ease of use. But on my old hardware it wasn't really flying. Right now I don't see a need to try it, as my Xen hypervisor solution just blows away anything I've seen so far in terms of virtualization, though I have to do some real world stuff to confirm.

As for me, my goal is to run a few non-graphical servers as domU virtual machines alongside a graphical dom0 that can at least play youtube videos without stuttering. And since I have no need for a graphical environment on my domU virtual machines, I have no need for graphical passthrough. I could accomplish something similar using Ubuntu 12.10 as a host for VirtualBox, but Xen would be a more stable environment for my virtual servers.

As much as I want to stick with Linux running as dom0 under Xen, I have found that, in view of the video card issues that I'm having with Linux running under Xen, Windows 8 under Hyper-V is currently a better alternative for me: In Windows 8 running as the control domain under Hyper-V, I get a Windows Experience of 5.3 with my current Nvidia GT 610 (not great, but good enough for now) and I get the stability of virtual machines running under Hyper-V, which is a bare-metal hypervisor that is very similar to Xen. Also, although I don't have much reason for a second graphical environment, I can also run Ubuntu 12.10 Desktop as a graphical virtual machine with reasonable video performance.

I think with a little better AMD GPU card you could get a good Xen hypervisor solution for your needs. It takes more to set it up, but once it works it works great. I haven't given Hyper-V a shot - doesn't that cost quite some money? I spent enough for now on the Windows retail license.

Good luck and let us know how it works.

[GizmoChicken]

@powerhouse: Thanks again for all the additional info! Yep, I'll definitely give an AMD GPU a try.

About VirtualBox, the newer versions take advantage of VT-x/AMD-V technology found on many newer CPUs. Using that feature, VirtualBox can be nearly as fast as Xen for many applications. If you haven't tried VirtualBox on a VT-x/AMD-V enabled CPU, you might want to give it another try. And if you do, be sure to enable hardware virtualization on the acceleration tab.

About Hyper-V, to compete with the likes of Citrix and VMware, Microsoft offers a free version (or at least free when I last checked) that includes a "control" domain (analogous to dom0) with just enough functionality to manage your virtual machines. You can learn more about the free version and get a copy of it here:

http://www.microsoft.com/en-us/server-c ... -v-server/

Unfortunately, the above free version doesn't give me sufficient desktop functionality to meet my needs. So instead of that free version, I'm using the version of Hyper-V that comes with the Windows 8 Release Preview, which is currently available under under a free trial license. You can get a copy here:

http://windows.microsoft.com/en-US/windows-8/download

If I didn't need a graphical desktop on dom0, I would use XenServer or XCP as my hypervisor/dom0, both of which are extremely stable on my computer. And like I said before, although I would prefer to use Xen/Linux, at least as of now, Hyper-V works well without any headaches. Once my trial license expires, I'll consider whether to buy a full Windows 8 consumer license (probably about $150) or return to Xen. Maybe by then I'll have worked the bugs out of graphics support for dom0. My virtual servers will, of course, remain Linux-based.

P.S. On a side note, I was shocked that Windows 8 doesn't include a version of the "start menu" that has been present on every version of Windows since Windows 95. To cure that defect, I installed "Classic Shell" which is an open source menu for Windows 8. You can find it here:

http://classicshell.sourceforge.net/

With a little tweaking, Windows 8 will look and feel just like Windows 7, but perform much better.

[powerhouse]

Thanks for the explanations. I never considered nor tried Windows 8 because of the missing start menu. I have no use for a tablet like GUI on a desktop machine with 26" screen. Even Ubuntu and more so Fedora turn me off in their default setup. I need my applications organized in a menu, and desktop shortcuts/links/app launchers for the most common tasks without reinventing the wheel.

The Linux Mint desktop is just perfect for my needs. I have only one task bar on the bottom, with menu button and app launchers for some common tasks, desktop switcher, and hardware sensor overview for monitoring my core temps and critical voltages. The core temp readings show me immediately how many cores are in use or how busy my machine is.

Using two VGA adapters with the AMD as primary adapter for Linux dom0, the nouveau Nvidia driver caused problems detaching the secondary Nvidia card. I just blacklisted the nouveau driver and all is fine now (have no need for it since my secondary Nvidia card is only used by Windows domU).

Under Windows (domU) I installed the signed GPLPV drivers for the disk and it works fantastic. It increased my Windows Experience Index from 5.8 to 7.8 for the hard drive data transfer speed.

VirtualBox improved hardware acceleration and VT-d support, but as far as I know it does not yet support VGA passthrough. Perhaps in time I will give it a try under native Linux Mint (not hypervisor, as it doesn't make much sense to test it there).

I am very weary about putting Windows as primary OS (even hypervisor) on my computer. I find it much more difficult to get things working under Windows, and the Microsoft support website is often less than useful (though it improved somewhat). Windows user forums are also a mixed experience. Besides, I use some demanding applications under Linux to rip my CDs and DVDs for my media streamer and find that Linux gives me better options. There is little under Windows that I use except the OS itself and specific apps I need to edit photos. And we all know that Windows is more likely to get infected by malware than Linux.

Under Xen I can take snapshots of my Windows domU and restore it when needed, without requiring an installation DVD, same goes for Linux. I also keep a bootable Linux Mint stick to recover my system in case of failure. So if I made some bad adjustments to config files, or installed packages that break my system, it's usually quite easy to fix without going through a total reinstallation.

Of course everyone has different preferences and experiences. Me I'm happy with Linux for most of what I need, Windows and its applications fill in for the rest.

Thanks for your ups on how to get a similar setup under Windows 8. It's always good to have alternative options.

[GizmoChicken]

@powerhouse: Thanks so much for the extra info. Much appreciated! And yep, I would definitely stick with a Xen/Linux combo if I could get it working sufficiently well without spending a bunch more on hardware.

No hurry, but if you have some time, would you mind answering a few questions? They are:

1) You mentioned that Video on dom0 was a bit choppy on your AMD 6450 card. Have you tried video on native Linux (without Xen) to determine whether it is any less choppy than when displayed on dom0? (I ask because, if equally choppy, then the choppiness is probably is due to the card not having enough power, in which case I might take a chance and buy a slightly more powerful AMD card. But if not choppy when booted directly to Linux without Xen, then the problem would seem to be with the AMD driver, in which case I don't want to waste any more money on an AMD card.)

2) I know that it works in dom0, but do you know whether your AMD 6450 card supports GPU passthrough from a domU? (I'd like to give GPU passthrough a try, but I don't want to spring for a Quadro 2000.)

3) Does your Quadro 2000 have HDMI output? If so, does the audio pass through?

Thanks in advance for any info you can provide concerning the above!

If I could get GPU passthrough to work (along with audio passthrough) using a relatively cheap GPU, I would probably use XCP 1.5 (which is an open source version of Citrix XenServer, but with a few more features) or possibly XCP in Ubuntu Server 12.04 LTS as a headless dom0 and then put my graphical desktop on a domU. That way I could shut down the graphical desktop (which I use rarely) without affecting my servers. And supposedly, keeping graphics off of dom0 makes for a more stable system with less overhead. Not sure how much of a difference it makes, though.

I notice that, back when you only had a single graphics card, you planned to devote that card to a domU and to rely on ssh to access dom0. Any thoughts of using XCP or similar (which you can manage with XenCenter, OpenXenManager and/or ssh) as a headless dom0 with Linux Mint as another domU?

About Windows 8, yep, I agree that the lack of default "start menu" is off-putting. But in many ways, the "Classic Shell" addition is actually better (more configurable) than the old Windows 7 start menu. So really, now that I've found "Classic Shell" I'm glad that Microsoft left out the start menu.

About VirtualBox, you are correct about not trying it under Xen. At least for me, guests won't boot within VirtualBox running on dom0. Also, you correct that GPU passthough won't work with VirtualBox.

[powerhouse]

@GizmoChicken: I'm happy to share information.

1. Sorry, not yet been able to run native Linux (without hypervisor). Have been transferring a bunch of disks and copying and rearranging my data. Unfortunately 2TB disks don't copy so fast. Will post my experience with full screen youtube viewing under native Linux later.
Remark: Watching video files with VLC or Movie Player is fine.

2. No, I haven't tested the AMD 6450 for VGA passthrough, though I had considered it at the beginning. Adobe Lightroom and Photoshop make use my Quadro 2000 card's FPU capabilities to assist in rendering pictures. The AMD 6450 has got nothing to compare with that. Also, my Quadro 2000 uses 10 bit per color channel, offering better gradation in color tones when using a high-end screen.
I would go with the tested AMD (or Nvidia) adapters, see here: http://wiki.xen.org/wiki/XenVGAPassthroughTestedAdapters - this is certainly not up-to-date. I also need to write to inform them about the Quadro 2000.
For some infos on passing through a secondary graphics adapter, see here: http://wiki.xen.org/wiki/Xen_VGA_Passthrough and here http://wiki.xen.org/wiki/SecondaryGPUPassthrough.

Here a nice how-to for Fedora users: http://www.overclock.net/t/1205216/guide-create-a-gaming-virtual-machine - the thread is lengthy but contains some information on successful VGA passthrough.

Here a short how-to for Ubuntu-based systems: http://gro.solexiv.de/2012/08/pci-passthrough-howto/ - see also my comments towards the end.

Here my fresh how-to on this subject (your comments are most welcome): http://forums.linuxmint.com/viewtopic.php?f=42&t=112013.

This information above should help you check your hardware for compatibility. If you have an Intel CPU, it must support VT-d. The same goes for the motherboard - you need a BIOS that allows you to use VT-d. This paired with a compatible graphics adapter should get you to a working system.

3. The Quadro 2000 has a DVI port (which I use) and two Display Ports. It has integrated audio support that can be used via the display ports. Here audio specs right from the manufacturer (PNY):

DisplayPort and HDMI Digital Audio
Support for the following audio modes: Dolby Digital (AC3), DTS 5.1, Multi-channel (7.1) LPCM, Dolby Digital Plus (DD+), andMPEG-2/MPEG-4 AAC
Data rates of 44.1 KHz, 48 KHz, 88.2 KHz, 96 KHz, 176 KHz, and 192 KHz
Word sizes of 16-bit, 20-bit, and 24-bit

If you don't have DisplayPort on your screen, you could use a DisplayPort-to-HDMI adapter.

Unless you have a specific need for a Quadro 2000 card, like graphics design, photo or video editing, medical imaging, or CAD-CAM, I would go for more mainstream AMD models that are VGA passthrough compatible. In Nvidia's lineup of "multi-OS" graphics cards, the Quadro 2000 is the cheapest of them all. Don't get me wrong, I like my Quadro 2000 very much, but it's much too expensive for its performance when gaming.

The above link to VGA passthrough compatible cards also lists the Nvidia 8800 GTS, if you want to give Nvidia a try (check the link for details).

[GizmoChicken]

@powerhouse: Thanks once again for all the information. Extremely helpful!

Yep, since my only use for a graphical desktop is, at least on this system, to play video, including streaming flash video, a Quadro 2000 is way beyond my needs (and budget). So like you said, a cheaper AMD would probably be the best way for me to go. Just wish I had known that before buying Nvidia GT 610.

I'm drawn to the AMD 6450 because, like my Nvidia GT 610, it is available in a fan-less version, and so wouldn't add any noise to my otherwise reasonably quiet system (which is set up in my media room). But I'm concerned by your reports of choppy flash video when using your AMD 6450 in dom0, and now I'm wondering if I shouldn't go for something a little more powerful, such as an AMD 6670, the fan for which is reportedly fairly quiet.

Even though I have sort of accomplished what I want to do using Hyper-V, the purist in me really wants to get this working with Xen. And I haven't given up on the Xen approach yet. So thanks again for all the info! I'll try to put it to good use!!

[powerhouse]

@powerhouse: Thanks once again for all the information. Extremely helpful!

Yep, since my only use for a graphical desktop is, at least on this system, to play video, including streaming flash video, a Quadro 2000 is way beyond my needs (and budget). So like you said, a cheaper AMD would probably be the best way for me to go. Just wish I had known that before buying Nvidia GT 610.

I'm drawn to the AMD 6450 because, like my Nvidia GT 610, it is available in a fan-less version, and so wouldn't add any noise to my otherwise reasonably quiet system (which is set up in my media room). But I'm concerned by your reports of choppy flash video when using your AMD 6450 in dom0, and now I'm wondering if I shouldn't go for something a little more powerful, such as an AMD 6670, the fan for which is reportedly fairly quiet.

Even though I have sort of accomplished what I want to do using Hyper-V, the purist in me really wants to get this working with Xen. And I haven't given up on the Xen approach yet. So thanks again for all the info! I'll try to put it to good use!!

I come more and more to the conclusion that I will replace my 6450 very soon. Hell, it can't even scroll a browser without showing diagonal distortions. I don't care if it's the card or the driver (AMD proprietary driver which seems to work fine otherwise, I mean except for poor performance of the bundle).

I'm usually drawn to Nvidia cards since I never had performance issues nor driver issues using the proprietary driver, except for Xen. By the way, my old PC has a 5-6 year old Nvidia card with passive cooling that way outperforms this AMD card.

My current system is very quiet, despite having 9 out of 10 fans running all the time. Hope you find a good solution - it's a pity Nvidia with its own driver doesn't work under Xen.

[GizmoChicken]

I come more and more to the conclusion that I will replace my 6450 very soon. Hell, it can't even scroll a browser without showing diagonal distortions. I don't care if it's the card or the driver (AMD proprietary driver which seems to work fine otherwise, I mean except for poor performance of the bundle).

I'm usually drawn to Nvidia cards since I never had performance issues nor driver issues using the proprietary driver, except for Xen. By the way, my old PC has a 5-6 year old Nvidia card with passive cooling that way outperforms this AMD card.

My current system is very quiet, despite having 9 out of 10 fans running all the time. Hope you find a good solution - it's a pity Nvidia with its own driver doesn't work under Xen.

Yep, it's a shame that Nvidia doesn't support Xen dom0 for most of their cards.

I recently replaced my Nvidia GeForce card with a Gigabyte Radeon HD 6670 and it seems to work pretty well, at least for watching HD video and so forth, with Ubuntu 12.10 beta 2 as dom0 using the open source driver. And the card's 100mm fan is nearly silent under normal use. But to get HDMI audio output working with the open source driver, I had to edit the "GRUB_CMDLINE_LINUX_DEFAULT" line in "/etc/default/grub" to read as follows:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash radeon.audio=1"

Interestingly, although my 6670 worked well with the open source driver, I couldn't get it to work with Ubuntu 12.10 beta 2 as dom0 using the AMD proprietary driver. Xorg doesn't seem to start. There is probably a fix for this, but I'm satisfied with the open source driver, so I haven't spent much time on it.

I also tested my 6670 with Mint Linux 13 with Cinnamon as dom0 using the AMD proprietary driver. It seemed to work well, although I didn't spend much time with it.

[powerhouse]

I come more and more to the conclusion that I will replace my 6450 very soon. Hell, it can't even scroll a browser without showing diagonal distortions. I don't care if it's the card or the driver (AMD proprietary driver which seems to work fine otherwise, I mean except for poor performance of the bundle).

I'm usually drawn to Nvidia cards since I never had performance issues nor driver issues using the proprietary driver, except for Xen. By the way, my old PC has a 5-6 year old Nvidia card with passive cooling that way outperforms this AMD card.

My current system is very quiet, despite having 9 out of 10 fans running all the time. Hope you find a good solution - it's a pity Nvidia with its own driver doesn't work under Xen.

Yep, it's a shame that Nvidia doesn't support Xen dom0 for most of their cards.

I recently replaced my Nvidia GeForce card with a Gigabyte Radeon HD 6670 and it seems to work pretty well, at least for watching HD video and so forth, with Ubuntu 12.10 beta 2 as dom0 using the open source driver. And the card's 100mm fan is nearly silent under normal use. But to get HDMI audio output working with the open source driver, I had to edit the "GRUB_CMDLINE_LINUX_DEFAULT" line in "/etc/default/grub" to read as follows:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash radeon.audio=1"

Interestingly, although my 6670 worked well with the open source driver, I couldn't get it to work with Ubuntu 12.10 beta 2 as dom0 using the AMD proprietary driver. Xorg doesn't seem to start. There is probably a fix for this, but I'm satisfied with the open source driver, so I haven't spent much time on it.

I also tested my 6670 with Mint Linux 13 with Cinnamon as dom0 using the AMD proprietary driver. It seemed to work well, although I didn't spend much time with it.

Thanks for your impressions on the AMD 6670. I'm considering this card as well, having had a look at some benchmarks over at http://www.phoronix.com/scan.php?page=article&item=radeon_mai_2012&num=1. Should have read these benchmarks or their review before buying the 6450.

About closed source drivers: I just upgraded to the 3.2.0-31-generic kernel and had to reinstall the AMD proprietary graphics driver. It wouldn't run with the post-release update version, but it runs fine with the regular Catalyst driver on Linux Mint 13 Mate under dom0.

One last thing, though probably not relevant to you anymore: I was able to get rid of the diagonal lines when scrolling by enabling "Tear Free Desktop" in the AMD Catalyst Control Center. But now I can't see Youtube movies fullscreen - it gets stuck after a few frames. It's a little too much for this graphics card.