alt Hacker NewsReBarUEFI: Resizable BAR for almost any UEFI system
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These kind of BIOS modding shenannigans is why I got interesed in Coreboot, so that enhancing a Firmware capabilities becomes possible without touching propietary tools/code.
Other similar mods included adding NVMe Boot capabilities to older Firmwares that didn't supported them so that you could boot from modern NVMe drives if you used some kind of adapter (As none of those Motherboards have M.2 Slots, but you can use them with a PCIe-to-M.2 adapter card). Also adding required stuff to get certain CPUs booting in Motherboard that were never officially supported (Depending on generation, could be as simple as adding new CPU Microcode).
What does this do? I perused the README but I'm still clueless on what the purpose and use-case is for ReBAR.
(Posting this under the assumption others will also appreciate a bit of quick context.)
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.
Since I don't want to tinker with my HP Firmware, a brief investigation led me to OpenCore's ability to enable Resizable BAR in the bootloader before Windows boots. Not sure how reliable it is. https://github.com/xCuri0/ReBarUEFI/discussions/118
"Do I need to flash a new UEFI image on the motherboard, to enable ReBAR on the GPU ? Yes, this is how it works for Turing GPUs (GTX 1600 / RTX 2000)."
Sounds scary. Like there is a good chance to brick the motherboard permanently. I think i'm going to skip this for my ye olde pc with crappy GTX 1660 Ti card. Can't afford a new system.
Finally, a way to squeeze more life out of my old gaming rig. My 3070 will appreciate this.
Can anyone verify if this works on a Lenovo Thinkpad? I checked the List of Working Motherboards [1]. They often have Thunderbolt but no way to enable ReBAR.
Do you inject a DXE into OEM firmware for that map, or wait for the board vendor and live with the small window?
On my linux machine chrome was crashing almost daily before activating rebar by patching bios.
This made me finally try to migrate an old system of mine. Migrate what you ask? Well, ReBAR driver stuff requires GPT-based disks, and on that machine it's still running on MBR...
Tempted to see if this will work on the work dell laptop, which hardware supports rebar, but Dell just can't be assed to enable it - use an external ARC GPU to properly support 3 screens (again, Dells awful drivers / firmware - the same hardware supports 3 screens just fine).
Sweet! Been wishing for ReBAR on my X99 rig forever. This could finally make that old setup sing with a modern GPU.
Should I be enabling this on a workstation setup doing ML ? Mostly GPU protein folding
I am in need of this from the opposite direction - an RTX 3080 20G BIOS which adds ReBAR to the card.
Claude tells me the BAR is outside the encrypted part of the card firmware so theoretically should be possible?
FYI: Resizable BAR (Base Address Register) is a PCI Express feature that removes the traditional 256MB memory limit, allowing your CPU to access your graphics card's entire VRAM at once for a potential 5% to 15% boost in gaming performance