d4 Q-Code

[UserX]

The symptom

With the NVidia RTX PRO 6000 Blackwell installed in either x16 slot the board hangs at Q-Code d4 (“PCI resource allocation error. Out of resources”) during early POST; no video output. RTX 4090 FE and a RTX 5090 both boot fine in the same slot.

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What I’ve already done (yes, all of it)

BIOS & firmware

• Flashed 2001 (current non-beta) and rolled back to 1801, 1703 clearing CMOS after every flash.
• Updated ME firmware
• Reset BIOS
• Loaded Optimized Defaults between tests.

PCIe-related toggles

• Above 4G Decoding (on/off) – no dice
• Re-Size BAR (on/off), SR-IOV, ASPM, PCIe Link Speed auto but forced to Gen 3/4/5.
• CSM, Secure Boot, Fast Boot each enabled/disabled in every feasible combo.

Lane & resource sanity checks

• Pulled every drive from M.2_2, M.2_3, M.2_4, M.2_5 --M.2_1 is empty--, all SATA, all USB devices.
• Tested both x16 slots to see if POST progresses (it does not).
• Booted with one DDR5 stick at 4800 MT/s (no XMP) and with iGPU as primary.

Power & thermals

• Dual-metered the 12V-2×6 lead under load with a dummy card – rail is solid.
• Swapped to fresh cables just in case.

Physical & misc.

• Checked standoffs/backplate clearance, reseated CPU, inspected pins, verified no cooler over-tightening.
• Not able to test the GPU in another system ATM. Will open a post with PNY.

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Why I’m posting

It looks like the board simply can’t allocate the massive BAR space that Blackwell’s 96 GB VRAM demands. If anyone at ASUS (or fellow ROG tinkerers) has:

• A beta BIOS newer than 2001 (e.g., 21xx series?) with updated PCIe/bridge microcode, or
• A hidden switch/knob I’ve missed that relaxes PCIe resource mapping limits,
• Any other ideas on how to get this working
• Confirmation on my suspicion that the board just cannot allocate the resources.

I’m all ears. Happy to flash beta firmware and provide logs.

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System Specs

• ASUS Maximus Z790 Dark Hero
• Corsair H1500i
• 96GB Corsair Titanium DDR5 6600
• Intel 14900KS
• 4X Samsung 2TB 990 Pros
• Custom CPU Water cooling loop
• ElmorLabs BENCHLAB
• Open Benchtable V2

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UPDATE 5:01 PM 5/24/2025

• After more testing I was able to get it to boot from iGPU with the Blackwell installed. This is my intended setup which keeps the Blackwell's VRAM free and clear for AI/ML jobs.
  
  • Reset BIOS
  • Re-Size BAR Support (Disabled), SR-IOV Support (Disabled)
  • Primary Display (CPU Graphics), iGPU Multi-Monitor (Enabled), DVMT Pre-Allocated (64M), RC6 Enabled
  • CPU PCIe Link Speed forced to Gen 5.
  • CSM, Secure Boot, each disabled
• I will post more after checking stability and performance

[JohnAb]

Have you tried different PCIE x16 link speed settings? (under the advanced BIOS menu I think). I know you want max speed, but it might things going. 

Otherwise, make sure the GPU firmware is up to date and/or contact Nvidia. They ought to have decent support for their flagship GPU. 

[UserX]

I gave PCIe gen 3, 4 and 5 a try but had no success. I started conversations with ASUS, PNY and NVidia. Thanks for the reply.