[Request] Above 4g decoding for P8Z68-V PRO/GEN3

I would like to use a Tesla80K for a project but my motherboard doesn’t seem to have the options I need by default. New here and a little unfamiliar with using forums in general so please feel free to let me know if I’m not handling things correctly.

No you’re not…
First of all…regarding the “new” to forums… cant you at least report what are the issues with the card/system board, you came across, in order to users can give some directions?
Is this how you approach a TI department of a repair shop and…“i dont have the options…”
What options are talking here sir? Are we guessing wizards here?
A 6.000€ card in a 50€ 2012 motherboard… did you get it free?
Oh well…another day another surprise.

EDIT: Go for it: [Experimental] Resizable BAR DXE driver - BIOS/UEFI Modding / BIOS modules (PCI ROM, EFI and others) - Win-Raid Forum (level1techs.com)

Enabling hidden 4G decoding · xCuri0/ReBarUEFI Wiki (github.com)


The one in the title, above 4g decoding. Also sorry for being poor I guess? I’m using what I can afford.

@Edy I don’t think these cards use Resizable BAR but just do all the patches/DSDT modifications and add ReBarDxe module. That should get the card working for you (with 4G decode on) because these boards have an artificial limit preventing >4GB BAR by default. You also will need to use less than 32GB of RAM installed.

If the card needs 32GB BAR it’s unlikely to work due to how the BAR allocation works on Ivy Bridge. Technically it could fit and work with 16GB RAM if the BIOS would allocate it first at 0x800000000 (32GB) (all BARs must be aligned with their size) so it would extend till 0x1000000000 (64GB) (maximum physical address supported by Ivy Bridge). But that’s not the case since the BIOS allocates other devices before the GPU.

It may be possible to make a patch/module to fix this by doing bottom to top allocation instead of the default top to bottom. Along with also changing the ME address (MESEG_BASE)

TLDR: if you want something easy just buy a Skylake+ board or Chinese X79/X99 with 4G decoding to use with it. If you want to use it on desktop Sandy/Ivy Bridge or Haswell be prepared to have to write an override for UEFI AllocateMemorySpace to use bottom to top allocation.

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@ Kuri0
Correct me if im wrong…
The funny “stuff” here is… isnt this a Tesla K80 a server Dual GPU processing board without outputs?
How is the OS/bios of the Z68 handle a secondary card if he needs a signal output card/iGPU for visualization, regarding the 4GB DEC?

EDIT: Ok the iGPU to work…but i suspect we wants to take advantage of 4GB/REBAR from the K80… just curious, lets see if i didnt scared him offf and reports it back if he proceeded further.

@MeatWar Shouldn’t the iGPU just work ?

The challenge is if the K40 has a 32GB BAR then AllocateMemorySpace will have to be overridden to provide bottom to top allocation. If it has 16GB BAR it should just work with all the RebarUEFI patches/DSDT edit like multiple people have successfully used 16GB BAR GPUs on Sandy/Ivy Bridge