ReBarUEFI is a Boot Time Module that Enables Resizable BAR on Some Older Platforms

[btarunr]

Officially, support for resizable BAR on the Intel platform begins with the 10th Gen Core "Comet Lake," and for AMD, the Ryzen 3000 "Zen 2." It is a PCI-SIG feature that allows the software to see the entire amount of video memory on your graphics card as a single contiguous addressable block, rather than through 256 MB apertures—a workaround for the original PCI Express specification as the industry was transitioning to it from AGP. The PCI-SIG had introduced resizable BAR way back during the PCI-Express 2.0 specification (late 2000s), although none of the GPU or platform vendors of the time bothered to implement it. Resizable BAR is known to have a positive impact on performance for modern GPUs from NVIDIA and AMD; although its most profound performance impact is on the Intel Arc "Alchemist" GPUs, which suffer a large performance penalty without it.

ReBarUEFI by xCuri0 is a UEFI DXE driver mod, which requires you to know how to modify the UEFI firmware of your motherboard. The ReBarUEFI mod calls for a motherboard that implements UEFI, the older legacy BIOS won't do. The industry transitioned to UEFI in the early 2010s, roughly around the time of Intel "Sandy Bridge." UEFI DXE drivers provide basic support for the various hardware on your system. The ReBarUEFI driver informs software that the platform is capable of resizable BAR. Some motherboards may require you to enable the "Above 4G Decode" setting. The author claims that users on platforms as old as 2nd Gen Core "Sandy Bridge" have had success in getting resizable BAR to work.



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[Jism]

It's confusing if this is for just Sandy bridge / prior or also AMD, i.e 1x00 or 2x00 series (Ryzen) or even Bulldozer FX.

 

[Assimilator]

Yes, let's enable reBAR on platforms that are so old that installing a GPU that benefits from reBAR has no point because it will be so severely CPU-limited.

 

[stimpy88]

We can thank nGreedia for not letting all their slightly older cards use this standard.

My 2070 could do with all the help it can get.

 

[Assimilator]

We can thank nGreedia for not letting all their slightly older cards use this standard.

Yes, their older cards that don't benefit from this feature at all so there was no point in implementing it. So many geniuses here on TPU.

 

[generaleramon]

It's confusing if this is for just Sandy bridge / prior or also AMD, i.e 1x00 or 2x00 series (Ryzen) or even Bulldozer FX.

I managed to get reBar/SAM working on a Biostar X370GTN + Ryzen 1700 + RX5700XT. Pretty easy, i just needed to add the FFS module with UEFItool, save, and than flash the new modded bios.

 

[b1k3rdude]

Modifying your BIOS from an unofficial source, would could go wrong with that...

 

[generaleramon]

Some people really don't like to have fun
P.S. The .ffs module itself is provided pre-compiled so that is easier to use, but the source code is there, you can compile it yourself, plus, i can't see any closed-source blob. Looks decent to me

 

[SOAREVERSOR]

We can thank nGreedia for not letting all their slightly older cards use this standard.

My 2070 could do with all the help it can get.

Preach on brother! I've got a working GeForce 3 Ti500 in a retro box that could use this. Shame nvidia, shame!

 

[generaleramon]

Preach on brother! I've got a working GeForce 3 Ti500 in a retro box that could use this. Shame nvidia, shame!

I checked on youtube and even a 6500XT get some extra fps i some games with SAM enabled, i know i know, very little, but still, for free. And even if i get nothing out of it, what i love is that you can do it, breaking the rules.
A 2070 is probably 50%+ faster than that, imagine having a 5800X3D on a X370 MB and not being able to use reBar/SAM because AMD decided that you need a 5xx MB to do that.
We mod gpu bioses and use weird softwares and registry hacks every day to get that extra 1%, why is this Bios Mod to get an extra free feature such a big deal now?

 

[SOAREVERSOR]

I checked on youtube and even a 6500XT get some extra fps i some games with SAM enabled, i know i know, very little, but still, for free. And even if i get nothing out of it, what i love is that you can do it, breaking the rules.
A 2070 is probably 50%+ faster than that, imagine having a 5800X3D on a X370 MB and not being able to use reBar/SAM because AMD decided that you need a 5xx MB to do that.
We mod gpu bioses and use weird softwares and registry hacks every day to get that extra 1%, why is this Bios Mod to get an extra free feature such a big deal now?

I've got a 2080 super in a spare joke machine for the SO even though she rarely plays games and I'm not complaining! New features come with new generations.

As for modding this has always been the case. Back in the good old days you could mod geforce cards into quadros and when that went away I didn't complain as it was never supported in the first place! I just coughed up the cash for a quadro like a normal human being.

 

[Shou Miko]

This is actually interesting I most say.

 

[stimpy88]

Yes, their older cards that don't benefit from this feature at all so there was no point in implementing it. So many geniuses here on TPU.

Just like they said about the 30x0 series showing no benefit... Until the backlash made nGreedia update their bioses, then the benefit was shown in many games, and still does. I think you're the one showing genius levels of copeium abuse to "prove" your point here.

 

[Tomorrow]

Yes, let's enable reBAR on platforms that are so old that installing a GPU that benefits from reBAR has no point because it will be so severely CPU-limited.

I very much doubt that cards such as RX 580 etc are going to be bottlenecked by even Sandy Bridge series of CPU's. Yes 5700 XT "may" be bottlenecked as it's faster than my GTX 1080 was that got bottlenecked by 2500K OC'ed to 4.7Ghz.

We can thank nGreedia for not letting all their slightly older cards use this standard.

My 2070 could do with all the help it can get.

Same here with RTX 2080 Ti.

Yes, their older cards that don't benefit from this feature at all so there was no point in implementing it. So many geniuses here on TPU.

Ah yes the age old Nvidia excuse for screwing over their older series owners. They never offer any proof of this supposed "no benefit" and want us to take their word as the truth. Same with frame generation. FSR3 works pretty well on 20 series. Nvidia never bothered because it's extra work for them and they rather incentivize sales of newer cards. Same with ReBAR that 20 series could benefit from, but requires new BIOS'es for the cards (not just the platform - motherboard and CPU).

Modifying your BIOS from an unofficial source, would could go wrong with that...

Unless like me you have a motherboard with dual-BIOS and even physical switches. From an not too distant (X570) era where these features did not add the cost of another entire motherboard like they do now. One of the BIOS chips is even socketable so worst case scenario - if the other that is soldered to the board dies one could swap out the socketable one anyways.

Just like they said about the 30x0 series showing no benefit... Until the backlash made nGreedia update their bioses, then the benefit was shown in many games, and still does. I think you're the one showing genius levels of copeium abuse to "prove" your point here.

Same with FSR supporting older Nvidia cards and frame generation working on those cards.

 

[prazola]

Yes, let's enable reBAR on platforms that are so old that installing a GPU that benefits from reBAR has no point because it will be so severely CPU-limited.

I got it working with his help months ago on my secondary PC, 4790@4.8GHz + RX 6800. The performance uplift is visible in a lot of games.
This rig can play Cyberpunk at 1080p with 99 GPU utilization.

It's confusing if this is for just Sandy bridge / prior or also AMD, i.e 1x00 or 2x00 series (Ryzen) or even Bulldozer FX.

It's not SB prior only.

Modifying your BIOS from an unofficial source, would could go wrong with that...

Because AMI BIOSes and relative closed source blobs are state of the art code...

 

[Lew Zealand]

Yes, let's enable reBAR on platforms that are so old that installing a GPU that benefits from reBAR has no point because it will be so severely CPU-limited.

Intel A380 in an Optiplex 7020 is a perfect candidate for this and Optiplex 7010s are already listed as working in the list. Expand your scope just a little bit to see solutions instead of complaining.

 

[Arcdar]

not "news" Myconst, a Ukrain content creator who focused a lot on "everything ali-express" (especially x79 and x99 platforms) for markets with less availability of "general stores" (so not central Europe) and gamers with low income had a video about enabling it on a x99 platform some time ago

I actually think its interesting that it works - and actually "well enough" to make it viable. And I disagree with the "the systems are too old to even consider adding a GPU that benefits from this" for two reasons - for one it seems to improve even older gens that are not on the "rebar makes the magic work" list and for some who get a budget GPU from the newer generations to keep playing in 1080p and can't afford more it's a great way to still get a decent improvement out of their old x99 systems (which, even for 1440p can be more than enough - they are not energy efficient and won't be in the top 10 FPS systems, but a v3 with turbo-unlock or a v4 from the 269x series is still more than potent enough to run most games more than decently for a package where you get it with a board and ram in the 140-180€ range compared to paying that for a 12/13/14th gen CPU alone).

 

[iameatingjam]

Yes, let's enable reBAR on platforms that are so old that installing a GPU that benefits from reBAR has no point because it will be so severely CPU-limited.

W/e, I think this is good news. I'm sure you don't need a 10th gen intel cpu to get some benefit from resizable bar on a A580 or something.

 

[Random_User]

I apologize for a dumb question. But is ReBar a solely HW feature, or it requires software support as well? I mean would the programs and games utilize this feature "out of the box", or need the application developers to include it first.
Considering it was integral part even of PCIE 2.0, it could benefit even the old games of the same time. But correct me if I'm wrong.

not "news" Myconst, a Ukrain content creator who focused a lot on "everything ali-express" (especially x79 and x99 platforms) for markets with less availability of "general stores" (so not central Europe) and gamers with low income had a video about enabling it on a x99 platform some time ago

I actually think its interesting that it works - and actually "well enough" to make it viable. And I disagree with the "the systems are too old to even consider adding a GPU that benefits from this" for two reasons - for one it seems to improve even older gens that are not on the "rebar makes the magic work" list and for some who get a budget GPU from the newer generations to keep playing in 1080p and can't afford more it's a great way to still get a decent improvement out of their old x99 systems (which, even for 1440p can be more than enough - they are not energy efficient and won't be in the top 10 FPS systems, but a v3 with turbo-unlock or a v4 from the 269x series is still more than potent enough to run most games more than decently for a package where you get it with a board and ram in the 140-180€ range compared to paying that for a 12/13/14th gen CPU alone).

How about systems with DDR2, which were capped at 8GB. Some people stil use them, as retro builds or daily drivers. These can benefit from modern low end GPUs, but the amount of system RAM is yet a limiting factor.
And even DDR3 systems are CPU bottlenecked. But it would be intersting to tinker with nonetheless. Especially on non-xeon regular configs.

 

[Arcdar]

I apologize for a dumb question. But is ReBar a solely HW feature, or it requires software support as well? I mean would the programs and games utilize this feature "out of the box", or need the application developers to include it first.
Considering it was integral part even of PCIE 2.0, it could benefit even the old games of the same time. But correct me if I'm wrong.


How about systems with DDR2, which were capped at 8GB. Some people stil use them, as retro builds or daily drivers. These can benefit from modern low end GPUs, but the amount of system RAM is yet a limiting factor.
And even DDR3 systems are CPU bottlenecked. But it would be intersting to tinker with nonetheless. Especially on non-xeon regular configs.

I don't know about DDR2-systems as I haven't heard of anyone being able to adjust the micro-code in a way to get it enabled but as you can see in the video the test-results show an improvement in general performance - and, I may add, as I enabled it on two x99 systems myself, a noticable difference in "lag". Even if the framerates didn't improve it is noticeable especially in games like CS, Overwatch and TheDivision2 where I have to say even with fixed framerates the overall experience is more "smooth" (even though this is subjective "feeling" it can also be proven by a frametime analysis which shows less "lag-spikes" / lower Frame-time-deviation with ReBar enabled )

 

[chrcoluk]

I apologize for a dumb question. But is ReBar a solely HW feature, or it requires software support as well? I mean would the programs and games utilize this feature "out of the box", or need the application developers to include it first.
Considering it was integral part even of PCIE 2.0, it could benefit even the old games of the same time. But correct me if I'm wrong.

It is both, The drivers which are software have to be written to support it as well as the underlying graphics API.

In terms of games, some games improve with it, other regress, so from a developer's point of view, you could write your game to optimise the benefits from the increased mapping and the software might improve as a result. A bit like how games not design with NVME in mind dont load much faster compared to SATA SSD, but then optimise it via DirectStorage and it takes off.

 

[Dragaan]

Yes, let's enable reBAR on platforms that are so old that installing a GPU that benefits from reBAR has no point because it will be so severely CPU-limited.

I love how the hardware marketing has so many people thinking this way... I was told I was stupid for wanting to upgrade my 1080 ti to something new on my z170+6700k system. People (including on this site) telling me it's a waste and to spend my money on a new cpu first. I'll be so bottlenecked. Blah Blah. I actually started believing it myself... going against my gut. I only play at 60fps (and mostly 4k), so I figured I'd still get SOME improvement over the 1080 ti... Turns out I had drastically UNDERestimated how much I would gain from a new card. I got a 7800XT and my performance in almost every game was doubled. Turned out there was an issue with that card, so I ended up getting a 4070 Super later on and I gained a little MORE out of that (so I was STILL gpu bottlenecked with the 7800XT in my games - all but 2 or 3 of them).

And, actually, while I was waiting for my 4070 Super to arrive at the store I ordered it from, I was able to try out a 7900XT a friend had. It was only then that I noticed a cpu bottleneck in a few more situations. BUT, in almost every game I cared about I still gained even more from the 7900XT and in most games my cpu was STILL no where close to tapping out. Just better and better performance. I have been pretty impressed with how much FPS I'm able to get out of a card like that with my ~8yr old system. And for gaming strictly at 4k/60fps (at max settings), it seems like anyone with a similar system to mine (z170+6700K) will benefit from any new card up to a 7900XT or 4070 Ti Super. Some games will STILL be gpu bottnecked, but that would be the smart place to stop (I wish I had the $$ for a 4070 Ti Super).

Can't wait to try out the ReBAR mod myself, as I already see that my motherboard (asus z170 sabertooth mark1) is on the confirmed-working list.

fwiw - Games where I am cpu bottlenecked (or very close to it) are Cyberpunk 2077 (I play at 4K on max with quality DLSS @60fps but I cannot use ray tracing on top of that), Witcher3 NGE DX12 version at 4K Max (again, I'm fine on Ultra+ but cannot enable ray tracing on top)... actually I'll just stop here. It's mainly only when I try and use ray tracing on top of 4K/Max settings in AAA games (ratchet & clank is another one). Interesting thing is that my GPU poops out at about the same point, both in "normal" power, in VRAM (12GB buffer w/ the Nvidia card :/ ), or both.

 

[Drash]

I love how the hardware marketing has so many people thinking this way... I was told I was stupid for wanting to upgrade my 1080 ti to something new on my z170+6700k system. People (including on this site) telling me it's a waste and to spend my money on a new cpu first. I'll be so bottlenecked. Blah Blah. I actually started believing it myself... going against my gut. I only play at 60fps (and mostly 4k), so I figured I'd still get SOME improvement over the 1080 ti... Turns out I had drastically UNDERestimated how much I would gain from a new card. I got a 7800XT and my performance in almost every game was doubled. Turned out there was an issue with that card, so I ended up getting a 4070 Super later on and I gained a little MORE out of that (so I was STILL gpu bottlenecked with the 7800XT in my games - all but 2 or 3 of them).

And, actually, while I was waiting for my 4070 Super to arrive at the store I ordered it from, I was able to try out a 7900XT a friend had. It was only then that I noticed a cpu bottleneck in a few more situations. BUT, in almost every game I cared about I still gained even more from the 7900XT and in most games my cpu was STILL no where close to tapping out. Just better and better performance. I have been pretty impressed with how much FPS I'm able to get out of a card like that with my ~8yr old system. And for gaming strictly at 4k/60fps (at max settings), it seems like anyone with a similar system to mine (z170+6700K) will benefit from any new card up to a 7900XT or 4070 Ti Super. Some games will STILL be gpu bottnecked, but that would be the smart place to stop (I wish I had the $$ for a 4070 Ti Super).

Can't wait to try out the ReBAR mod myself, as I already see that my motherboard (asus z170 sabertooth mark1) is on the confirmed-working list.

fwiw - Games where I am cpu bottlenecked (or very close to it) are Cyberpunk 2077 (I play at 4K on max with quality DLSS @60fps but I cannot use ray tracing on top of that), Witcher3 NGE DX12 version at 4K Max (again, I'm fine on Ultra+ but cannot enable ray tracing on top)... actually I'll just stop here. It's mainly only when I try and use ray tracing on top of 4K/Max settings in AAA games (ratchet & clank is another one). Interesting thing is that my GPU poops out at about the same point, both in "normal" power, in VRAM (12GB buffer w/ the Nvidia card :/ ), or both.

I'm using a 6900XT with my z170+6700k for 1080p high frame rate gaming. The CPU takes a hammering sometimes but I get by with framerates that are close to Wizz's review of my card with a way better PC. The wife runs a 7900XT with the same CPU/mobo, 1080p also. CP2077 2.0 hammered her, I recall the older version ran great for me even with some RT. Go figure. Looking to upgrade but I get by. Not sure what to expect for a £1k rebuild.

 

[FirstEver.eu]

I recently added the latest NVMe driver (NvmExpressDxe_5.ffs) and ReBAR support (ReBarDxe.ffs) to my old ASUS P9X79 Pro.
After activating ReBAR (256MB -> 16GB) I have a 3.5% performance increase in Cyberpunk 2077 v2.2 on my RTX 4070 Ti.

How to activate ReBAR:

1. Download and flash my modded BIOS: P9X79PRO (ReBAR).zip
2. Disable CSM in the BIOS.
3. Run this program in Windows to activate ReBAR: ReBarState.exe
4. Set the value to: 32
5. Reboot your system and check the ReBAR status in GPU-Z app
   
   
   

Benchmark 4K Ray-Tracing Ultra settings:

ReBAR Disabled:
Average FPS 92.35 / Min FPS 84.97 / Max FPS 100.60

ReBAR Enabled:
Average FPS 95.65 / Min FPS 88.57 / Max FPS 104.09

I think the performance is pretty good for a 13 year old platform.

What next with my X79 platform?

2023 (RTX 3070) - 3DMark Speed Way (score 3854)
2024 (RTX 4070 Ti) - 3DMark Speed Way (score 6097) +37%
2025 (RTX 50xx) - 3DMark Speed Way (over 10000 ?)

My overclocked 13-year-old platform has a result 10% better than the (new) computer with the same GPU tested by VideoCardz.com
I have no idea what specs they used, but probably top-of-the-line.

 

[Rightness_1]

I recently added the latest NVMe driver (NvmExpressDxe_5.ffs) and ReBAR support (ReBarDxe.ffs) to my old ASUS P9X79 Pro.
After activating ReBAR (256MB -> 16GB) I have a 3.5% performance increase in Cyberpunk 2077 v2.2 on my RTX 4070 Ti.

How to activate ReBAR:

1. Download and flash my modded BIOS: P9X79PRO (ReBAR).zip
2. Disable CSM in the BIOS.
3. Run this program in Windows to activate ReBAR: ReBarState.exe
4. Set the value to: 32
5. Reboot your system and check the ReBAR status in GPU-Z app
   
   
   

Benchmark 4K Ray-Tracing Ultra settings:

ReBAR Disabled:
Average FPS 92.35 / Min FPS 84.97 / Max FPS 100.60

ReBAR Enabled:
Average FPS 95.65 / Min FPS 88.57 / Max FPS 104.09

I think the performance is pretty good for a 13 year old platform.

What next with my X79 platform?

2023 (RTX 3070) - 3DMark Speed Way (score 3854)
2024 (RTX 4070 Ti) - 3DMark Speed Way (score 6097) +37%
2025 (RTX 50xx) - 3DMark Speed Way (over 10000 ?)

My overclocked 13-year-old platform has a result 10% better than the (new) computer with the same GPU tested by VideoCardz.com
I have no idea what specs they used, but probably top-of-the-line.

If I may ask, how did you mod the bios?