The R12 only support PCIe link speeds of X8 in the full mechanical X16 slot.
The bios for the RTX 3090 that is the latest available is actually not the latest version. The latest version was removed from the download section a while ago, nobody seems to know why. See this link for more information: Alienware RTX Bios files
If you flashed the bios from the DELL driver side, called 1.0.0.1, you will not have resizable BAR support in your video bios.
The R12 motherboard has no BIOS available that supports REBAR. So even if you had the latest Vbios installed, you would still not be able to use REBAR as it also needs motherboard support to enable it.
The R12 motherboard has no BIOS available that supports REBAR. So even if you had the latest Vbios installed, you would still not be able to use REBAR as it also needs motherboard support to enable it.
The R12 Bios 1.1.2 supports Rebar. The Bios file can be found here
I've extensively tested both 1.1.1 and 1.1.2 bios and prefer 1.1.2. Definitely better than 1.1.4 which nerfs the R12 beyond recognition..... Remember to disable UEFI capsule updates in Bios too so that Windows can't force load 1.1.4
I also downgraded my Bios to 1.1.2 However my resizable bar is disabled as well. Not sure what this means or does. I also saw on some youtube videos that the 3090 should be getting 16 lanes not 8. Are we limited to 8 due to dells bios?
When you downgrade the BIOS to a version that does not support Resizable Bar (REBAR), you will loose the ability to enable REBAR at the motherboard level.
As far as the 8 lanes go, that is an electrical wiring limitation and not BIOS related. It is a mechanical X16 slot length wise, and electrically wired up as X 8.
Because this is a PCIe 4.0 slot, your bandwidth is the same as an X 16 PCIe 3.0 slot. Even an RTX 3090 will not saturate that bus yet, so there's no effect on the performance of your video card at this point in time.
r72019
6 Professor
•
5.3K Posts
0
August 4th, 2021 07:00
SYQMichael
21 Posts
0
August 4th, 2021 04:00
And also the "Resizable BAR" shown "Disabled", no way to turn it on from BIOS version 1.1.4
Vanadiel
6 Professor
•
7.1K Posts
1
August 4th, 2021 05:00
The R12 only support PCIe link speeds of X8 in the full mechanical X16 slot.
The bios for the RTX 3090 that is the latest available is actually not the latest version. The latest version was removed from the download section a while ago, nobody seems to know why. See this link for more information: Alienware RTX Bios files
If you flashed the bios from the DELL driver side, called 1.0.0.1, you will not have resizable BAR support in your video bios.
The R12 motherboard has no BIOS available that supports REBAR. So even if you had the latest Vbios installed, you would still not be able to use REBAR as it also needs motherboard support to enable it.
SYQMichael
21 Posts
0
August 4th, 2021 06:00
Thanks @Vanadiel You reminded me, so I flashed back the original 3090 BIOS and enabled setting in BIOS too, now Resized BAR is Enabled.
So you mean the speed in R12 max can be shown is x8, not x16, am I right? Thanks.
r72019
6 Professor
•
5.3K Posts
1
August 4th, 2021 07:00
Yes. There's only 8 powered pcie lanes so you won't see x16 there.
Rabbitdude
2 Intern
•
509 Posts
0
August 4th, 2021 15:00
R12 has motherboard support for ReBAR, that came with bios 1.1.2. I use ReBAR on the R12 with the the 6800XT
SYQMichael
21 Posts
0
August 4th, 2021 17:00
Oops, sad...
Wardski1974
2 Intern
•
189 Posts
0
August 4th, 2021 19:00
The R12 Bios 1.1.2 supports Rebar. The Bios file can be found here
https://www.dell.com/support/home/en-au/drivers/driversdetails?driverid=2fhvp&oscode=wt64a&productcode=alienware-aurora-r12-desktop&dgc=SM&cid=414195&lid=spr5164890810
I've extensively tested both 1.1.1 and 1.1.2 bios and prefer 1.1.2. Definitely better than 1.1.4 which nerfs the R12 beyond recognition..... Remember to disable UEFI capsule updates in Bios too so that Windows can't force load 1.1.4
Rabbitdude
2 Intern
•
509 Posts
0
August 4th, 2021 19:00
A 3090 isn't even close to saturating a x8 Gen 4's bandwidth
Vanadiel
6 Professor
•
7.1K Posts
0
August 4th, 2021 20:00
Does 1.1.4?
SYQMichael
21 Posts
0
August 4th, 2021 23:00
Yes, 1.1.4. Must be with 3090 94.02.59.00.94 firmware too.
Stro3579
12 Posts
0
August 8th, 2021 08:00
I also downgraded my Bios to 1.1.2 However my resizable bar is disabled as well. Not sure what this means or does. I also saw on some youtube videos that the 3090 should be getting 16 lanes not 8. Are we limited to 8 due to dells bios?
Vanadiel
6 Professor
•
7.1K Posts
0
August 8th, 2021 10:00
When you downgrade the BIOS to a version that does not support Resizable Bar (REBAR), you will loose the ability to enable REBAR at the motherboard level.
As far as the 8 lanes go, that is an electrical wiring limitation and not BIOS related. It is a mechanical X16 slot length wise, and electrically wired up as X 8.
Because this is a PCIe 4.0 slot, your bandwidth is the same as an X 16 PCIe 3.0 slot. Even an RTX 3090 will not saturate that bus yet, so there's no effect on the performance of your video card at this point in time.