this fixes a real annoyance on older workstation boards where above 4g decoding is a requirement but the option isn't even in the bios menu. saw a build recently on an x79 board where it had to be exposed with a hand patched bios before anything like this or a modern gpu would work at all.
bigwheels 47 minutes ago [-]
What does this do? I perused the README but I'm still clueless on what the purpose and use-case is for ReBAR.
Moto7451 13 minutes ago [-]
Resizable Base Address Register. In short, rather than the 256MB of mapped memory available to the CPU for any PCI device, ReBAR capable devices can map larger memory to the CPU’s addressable memory space. Without ReBAR or sufficient tricks (that Intel GPUs lack) you have to shuffle 256MB chunks around between GPU and CPU.
wmf 41 minutes ago [-]
It allows the CPU to access all GPU VRAM. This improves gaming performance, especially for AMD GPUs.
willis936 13 minutes ago [-]
It should come with a warning label. If you're in a scenario where VRAM is being maxed out and thrashing main memory then ReBAR will worsen the frequency and magnitude of the stutters. I ran into this with a 3070 (8 GB) recently.
Moto7451 11 minutes ago [-]
I think you’re experiencing paging to main memory rather than anything ReBAR related. ReBAR itself reduces memory copy operations. It’s of course possible you’re experiencing some sort of BIOS bug.
mathisfun123 42 minutes ago [-]
> what the purpose and use-case is for ReBAR
Literally the second sentence in the repo:
> This provides performance benefits and is even required for Intel Arc GPUs to function optimally.
qudat 22 minutes ago [-]
Your quote doesn’t help me understand this project at all.
What is a BAR let alone a resizable one? Readme just jumps in, which is fine, but I’m not sure why this is on HN or why I should care.
pizza234 16 minutes ago [-]
ReBAR stands for "Resizable BAR (Base Address Register)" - it makes the CPU's access window into GPU memory resizable; instead of accessing VRAM in small chunks, the CPU can access much more at once, which can improve performance on some modern GPUs.
mathisfun123 11 minutes ago [-]
i literally don't understand how people move through life - do you expect every single link on this site (or any site) to be ELI5 for you specifically? do you not understand that some things require effort/homework on your part?
Literally the second sentence in the repo:
> This provides performance benefits and is even required for Intel Arc GPUs to function optimally.
What is a BAR let alone a resizable one? Readme just jumps in, which is fine, but I’m not sure why this is on HN or why I should care.