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Comment by confident_inept | Hacker News Reader

I'm really curious to see if these still rely heavily on resizable BAR. Putting these in old computers in linux without reBAR support makes the driver crash with literally any load rendering the cards completely unusable.

It's a real shame, the single slot a380 is a great performance for price light gaming and general use card for small machines.

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What is the newest platform that lacks resizable BAR? It was standardized in 2006. Is 4060-level graphics performance useful in whatever old computer has that problem?

Sandy Bridge (2009) is still a very usable CPU with a modern GPU. In theory Sandy Bridge supported resizable BAR but in practice they didn't. I think the problem was BIOS's.

Oh wow. That's older than I thought. This is definitely less of an issue than folks make out of it.

I cling onto my old hardware to limit ewaste where I can. I still gave up on my old sandybridge machine once it hit about a decade old. Not only would the CPU have trouble keeping up, its mostly only PCIe 2.0. A few had 3.0. You wouldn't get the full potential even out of the cheapest one of these intel cards. If you are putting a GPU in a system like that I can't imagine even buying new. Just get something used off ebay.

There were a lot of generations after Sandy Bridge which didn't have it; Sandy Bridge was just one generation that didn't really support it on the consumer side.

Consumer boards and CPUs didn't really support it well until after 2018. I upgraded away from a Zen+ system because it didn't support it.

On paper any PCIe 2.0 motherboard can receive a BIOS update adding ReBAR support with 2.1, but reality is that you pretty much have to get a PCIe 3.0 motherboard to have any chance of having it or modding it in yourself.

Another issue is that not every GPU actually supports ReBAR, I'm reasonably certain the Nvidia drivers turn it off for some titles, and pretty much the only vendor that reliably wants ReBAR on at all times is Intel Arc.

I also personally wouldn't say that Sandy Bridge is very usable with a modern GPU without also specifying what kind of CPU or GPU. Or context in how it's being used.

My old Ice Lake CPU was very much a bottleneck in lots of games in 2018 when I finally replaced it. It was a noticeable improvement across the board making the jump to a Zen+ CPU at the time, even with the same GPU.

ReBARUEFI was enough to get it working on an ASUS P8P67-something something when I tried it in January-ish.

[1] https://github.com/xCuri0/ReBarUEFI

Ryzen 2000 series processors don't support AMD's "Smart Access Memory" which is pretty much resizable BAR. That's 2018.

Coffee Lake also didn't really support ReBAR either, also 2018.

The newest platform is probably POWER10. ReBar is not supported on any POWER platform, most likely including the upcoming POWER11.

Also, I don't think you'll find many mainboards from 2006 supporting it. It may have been standardized in 2006, but a quick online search leads me to think that even on x86 mainboards it didn't become commonly available until at least 2020.

Congrats on a pretty niche reply. I wonder if literally anyone has tried to put an ARC dGPU in a POWER system. Maybe someone from Libre-SOC will chime in.

do you have a reference for power rebar support? just curious, I couldn't find anything with a quick look

Oh no... my POWER gaming rig... no..

If the firmware is open source, perhaps it could be retrofitted. For amd64 motherboards that do not have native UEFI support, retrofits are possible through this:

https://github.com/xCuri0/ReBarUEFI

ReBAR was standardized in 2006 but consumer motherboards didn't start shipping with an option to enable it until much later, and didn't start turning it on by default until a few years ago.

While "standardized" many implementations were so buggy to be unusable - we needed >4gb pcie mappings for a development board, and finding motherboards that actually worked was a PITA well into 2012 (when I left that project).

Yes, it even says so as a requirement on the box.

What I'm also interested in is whether they'll require a PCIE 4.0 motherboard or if a 3.0 x16 slot is fine.

Also whether their software properly supports VR now...

Yes, the slide deck mentions reBAR is still required.

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