That’s before,- I don’t really trust the modification just yet.
Is this expected?
Hi, with a Razer Core X and a Radeon 570 (MSI RX 570 ARMOR 8G OC), I’ve got this result :
Capabilities: [200 v1] Physical Resizable BAR
BAR 0: current size: 8GB, supported: 256MB 512MB 1GB 2GB 4GB 8GB
No BAR 2 for me.
The BIOS is not patched.
OS : Ubuntu 22.10, mainline kernel 6.2.2
Just to add another data point: I’m on an 11th gen mainboard on bios 3.10 with an Intel ARC A770 GPU.
I applied the patch mentioned by @Lee_Holbrook (by running setup_var_cv SaSetup 0x431 1 0x01 ) and successfully activated ReBAR support on Manjaro Unstable with Linux 6.2.6. This gave a noticeable fps improvement and finally make Blender on a 4k monitor responsive.
lspci -vvv reports:
Capabilities: [420 v1] Physical Resizable BAR
BAR 2: current size: 16GB, supported: 256MB 512MB 1GB 2GB 4GB 8GB 16GB
I have been running it like this 5 days without any new instability. This method also seems to survive reboots.
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After the BIOS patch (intel 12th gen):
Capabilities: [200 v1] Physical Resizable BAR
BAR 0: current size: 32GB, supported: 256MB 512MB 1GB 2GB 4GB 8GB 16GB 32GB
BAR 2: current size: 256MB, supported: 2MB 4MB 8MB 16MB 32MB 64MB 128MB 256MB
Update: ReBar is enabled as per GPU-Z
@Jean-Marc_Le_Roux thanks for the update!
What was it before? Was Bar 2 2MB?
I am not even sure yet what this Bar is used for.
Not sure. I just know it was disabled on Windows.
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Okay, figured it out:
BAR 0 means available space when ReBAR is on … and BAR 2 when ReBAR is off
So when ReBAR is not enabled, the CPU only gets access to a limited VRAM portion of the GPU.
Okay interesting, the tool’s BLOB release files work, but when building from source it can’t open the file… sigh
Now, why is this not available in the BIOS settings? Given how far back for older boards some vendors are making this available this makes me very sad.
Also, coreboot? 
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Is this BIOS variable flip/patch doable on 13th gen boards? I just got mine and I’m looking into enabling rebar as well.
I have exactly the same experience with my ARC A750 eGPU and an 11th Gen Framework… I jumped through the hoops to get that tool running (did nobody mention that you’ve got to get a UEFI Shell up somehow, too - and learn to use it (hint: it’s like DOS - FS0: is the USB stick, cd to the path, run it like a program, etc)? haha). Admittedly I didn’t get a “Before”, but in the After, it’s got a half-opinion - says it’s disabled in BIOS, but enabled in the specs.
Maybe it’s just confused by Thunderbolt?
BTW, the ARC A750 worked wonderfully (Satisfactory in DX12 at least locked at 60fps - the ARC is full of quirks and in DX11 it was struggling at 20fps, and Vulkan was a corrupt garbage fire) even before ReBAR tweak was applied.
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Hi Tristan, regarding your post about using the A770 on an 11th Gen Framework; may I ask…
- What eGPU enclosure are you using?
- Have you tried gaming on Manjaro? What is the performance like?
Can someone from Framework please post the 13th gen BIOS so we can try the same mod?
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Can anyone who has an AMD mainboard check if there happens to be a ReBAR option in the BIOS? I doubt that they changed it this time but I’m hoping so. It’s really frustrating that they refuse to add a control for it even though it’s already implemented under the hood.
Tried digging around - couldn’t find any option for ReBAR in 7040 BIOS version 3.02.
Atleast ya’ll have a bios firmware to mess around with 
(13th Gen Intel user here 
)
(Reposting/quoting Jean’s request in the slightly delusional hope that someone from framework would see it)
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I guess 13 owners are forgotten
Here is AMD 13 integrated graphics:
And with Sonnet eGPU enclosure:
Would be nice if we could enable ReBAR support somehow.
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As a Linux user who successfully utilized an 11th gen + rx590 eGPU setup in the past, I would love to see if this 7840U would run well with an ARC A580 or RX6700XT these days. Thank you for posting this data.
Check what address range AMD preallocates to the TypeC PCIe ports. With Intel, this range is by far not big enough to fit any GPU’s full VRAM. That’d need to be solved first. Only then is it a question of whether the BIOS would support ReBar itself (which it actually might, according to some reports here and it detecting ReBar for some eGPUs in some applications, even though it is not working). Unknown if there are deep limitations of the TB/USB4 controllers.
Here the example of DevMgr, view resources by connection:
Only ~450 MiB per port. Such limits have been pretty standard. My desktop Maple Ridge controller uses ~740 MiB (but that is dual port). Still a far cry from 8 or more GiB.
(Note there will be 2 ranges. One is smaller and for IO, the larger one is the one for the actual VRAM)
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