(Logical) VFIO Increments
One of the most common questions we get is: “how should I build a VFIO PC?”
Admittedly, this is a pretty hard question to answer, which is why we created this page. This table contains personally vetted parts along with explanations of the pitfalls of each component, as well as the fixes you’ll need to do depending on what you choose to buy. We constructed it in the hopes that it becomes a go-to reference for the passthrough gaming community.
Price totals are approximate and subject to change with the market. Also, please read our Affiliate Link Disclaimer.
Note: any columns without links are generally commodity components and will be expanded upon in their explainer sections, below.
ADVISORY: There is currently a flash-shortage in the GPU market, likely caused by mining demand. This shortage is rendering most mid to high-end cards unavailable or incredibly expensive. We will continue to link compatible lower-end cards, but we feel that recommending high end GPUs is somewhat out of our scope with the current supply issues. Be aware that any unvetted AMD products you buy may have the reset bug, and that any Nvidia cards outside of the Quadro and Tesla lines will suffer from the error 43 glitch.
A PSU can make, or quite literally, break your system. As such, we only list PSUs that come direct from reputable ODMs in the industry, particularly ones with good track records in the enterprise market.
Sometimes you can find a better deal on a PSU via rebadges, but the reseller brands (corsair, etc.) sometimes release revisions and products in the same series from less reputable Shenzen designers, and navigating the minutiae of the market tends to be a lot of trouble.
If you can find them, Seasonic, Super Flower, FSP, and Delta are the brands to look for.
It’s an HDD. Cheap, spins, keeps your data safe. You should have a few in your system unless you need absolutely silent computing for your recording studio, in which case I’m not sure why you’re here.
We like to recommend Toshiba and Hitachi HDDs over Seagate and WD, because the numbers from several wide spectrum evaluations put them at the lowest failure rates year over year (other than HGST, a subdivision of Hitachi that was bought out by WD recently) and they’re also consistently cheaper per GB. We’ll be listing best price/GB drives here soon, so be sure to check back if you’re interested in cheap and performant spinning rust.
There’s not a whole lot to say about RAM.
Intel platforms will pretty much take whatever you slot in, and the amount you can pass to your VM is the only relevant metric to passthrough gaming.
AMD platforms will need to be vetted according to your motherboard’s compatibility list, and Samsung B-Die kits will generally perform better. Ryzen does scale a bit more dramatically with increased frequency due to the way it’s memory subsystem and CCX interconnects work, but as long as it’s listed as compatible you shouldn’t run into any issues. Generally, you want to buy the cheapest sticks you can find from a reputable brand.
This is the card that your host machine will use when your Gaming VM is up and running. Platforms with iGPUs don’t need an additional card, but Intel HEDT and AMD platforms will. If you need to drive a lot of monitors, do GPGPU, or want to game on your host in addition to your VM, feel free to get a higher powered card. We’ve chosen the GT 710 as a catch-all Host GPU because it can drive multiple monitors, and only costs around $40 USD.
Note: choosing the same model of card, or in some circumstances, even the same manufacturer as you use on your guest VM can cause problems. A good rule of thumb is to go with AMD on the host if you use Nvidia on your Gaming VM, and vice versa. While not 100% necessary, this will avoid complicated vfio-pci and modprobe configurations.
One of the most important parts of your build, the guest GPU, will probably the most finnicky part of your VFIO gaming machine, and selecting one with high compatibility that fits your needs can be difficult. Here’s a quick rundown on what to look for in a guest GPU.
What’s a Guest GPU?
It’s the graphics card that you pass over to your virtual machine to enable high gaming performance. Ideally you would be able to share it between the host and guest, but we don’t live in a perfect world, so you (with a few new and very expensive exceptions) need one for each. On systems with an iGPU, this means you only need to buy one discreet card, but on AMD and intel HEDT platforms, you’ll need a Host card as well.
Miners will buy up a lot of models as soon as they hit the shelves, so even highly compatible models tend to be scarce at a certain level of performance. Generally, though, there are 2 routes you can take for effectively selecting a Guest GPU:
Nvidia — all the cards are “broken”
Luckily, they’re all broken in the same way. Nvidia’s drivers will abort with an error if you try loading them in a VM with a consumer card attached. There’s a well documented workaround though, and with a little extra work you can get them up and running. Audio and interrupt issues may reduce performance out of the box, too — but these problems also have several tweaks and fixes. The rule of thumb with consumer Nvidia cards is that you’ll need to google things like “error 43 fix” and “MSI interrupts” to get them up and running, but they all work with a little tweaking, more or less.
AMD — some work, some just plain don’t
AMD has no such driver restriction for their consumer cards, which means (at least in theory) that they should “just work.” And a lot of them do. The trouble is, some of the AiB partners’ BIOS modifications don’t play well with KVM. A badly put together vBIOS can harm or even completely stop a passthrough gaming VM from working as intended. There are several bugs caused by this issue, that are collectively known as “The AMD Reset Bug.” There are 2 levels of severity:
- [*] Hang on Crash — The VM will work normally, but if it crashes during normal use, it will fail to reinitialize and will only become available again on system reboot. This is the less severe of the two levels, and may not affect the user at all if they aren’t overclocking or experiencing other system instability.
- [**] Hang on Reboot — The VM will work normally, but will fail to reinitialize after it is shut off, only becoming available when the host reboots. This level of the bug will make the card incredibly inconvenient to use for passthrough gaming.
There are guest workarounds that do work for some cards, but they aren’t as well documented or tested as the Nvidia Fixes, so we attempt to curate bug-free cards as best we can on this page.
Building a computer is often compared to the children’s toy, Legos, by enthusiasts to demonstrate how easy it is to build your own. In that analogy, the motherboard is the studded base-plate. Everything gets plugged in here, and it serves as the foundation that the rest of your computer is built on.
Choosing the right motherboard is a twofold problem when it comes to VFIO. Not only do you need to carefully select for the right bios features and I/O, but you need to know how well the PCIe slots are isolated via it’s IOMMU groupings.
The problem is, no vendor lists the IOMMU layout on their boards, and the only information you can generally find is scattered in forum posts and may be years old. Furthermore, certain chipsets have quirks that, while known to community veterans, can stop newcomers in their tracks. Here, we provide personally (or in some cases community) vetted known working models for the range of products we recommend. If the part has issues that need working around, check the entry for asterisks, and reference them below.
[*] – ACS needed in some cases: generally this workaround means that the board functions fine for regular use, but the cpu-specific lanes may not isolate properly. If you want a 2 dGPU build instead of using the iGPU or a chipset slot on these boards, the ACS Override Patch will generally be needed.
[**] – ACS needed in all cases: This board was chosen for price, not performance or compatibility. The IOMMU groups will not be functional for 1 GPU passthrough builds without the ACS patch.
[†] – CSM disabled: For these boards, the CSM module needs to be disabled in the UEFI to allow the host gpu to work properly.
[‡] – EFIFB off: the efifb option needs to be disabled for the host GPU to boot properly from the chipset slot.
If you have known working new AMD GPUs, please contact us with your make, model and the severity of the reset bug, if present.