Leo-Patch 1.6 · Q1HY MoDT · Observations 14 October 2026
PCIe GPU enumeration plan
Changes to try, one reboot at a time.
Root cause is still unproven and no BIOS change has been performed by this manual. These tests deliberately isolate one firmware variable per reboot while preserving known-stable memory, kernel, and NVMe settings.
Guardrails
Boot the stable Ubuntu 24.04 6.8 generic kernel path, not the unstable 7.0.0 nvidia-bos kernel.
Preserve DDR4 2133 Gear 2 and 1.350 V VDDQ.
Do not alter RP1 / 00:06.0, the system NVMe path.
Do not use raw EFI writes for the hidden CPU ReBAR field at +0x42c.
Before and after each reboot, capture lspci -Dnn, lspci -Dnn -s 0000:00:01.0, and lspci -Dnn -d 10de:.
Record the result and restore baseline after every unsuccessful trial before changing the next setting.
Diagnostic focus: restore enumeration of CPU Root Port 2 without disturbing RP1/NVMe or known-stable DDR4 2133 Gear 2 memory settings.
Test 1 · not yet performed
Disable visible ReBAR, keep Above 4G enabled
The owner-hosted Leo archive changelog says this BIOS line disabled ReBAR by default for compatibility with some discrete VGA cards. This test isolates BAR sizing from the basic Above 4G MMIO aperture.
Reset rule: if the GPU still does not enumerate after this one change, restore the baseline before trying the next test.
Test 2 · not yet performed
Set RP2 PCIe speed to Gen2 temporarily
Gen2 is a diagnostic margin test for a fragile ES MoDT slot path. It does not prove a trace fault; it only checks whether a slower link lets RP2 train far enough to enumerate.
Reset rule: if the GPU still does not enumerate after this one change, restore the baseline before trying the next test.
Test 3 · not yet performed
If visible, set RP2 Detect Timeout to 500 ms
The stored value is 0 and no binary evidence proves what 0 means on this board. If the field is visible in BIOS, this is only a late-detect hypothesis test.
Reset rule: if the GPU still does not enumerate after this one change, restore the baseline before trying the next test.
Test 4 · not yet performed
Disable RP2 PCI Express Clock Gating
RP2 clock gating is enabled in the 14 October 2026 stored observations. Disabling it asks whether keeping the root-port clock active changes enumeration.
Reset rule: if the GPU still does not enumerate after this one change, restore the baseline before trying the next test.
Test 5 · not yet performed
Disable RP2 PCI Express Power Gating
This is a power-state hypothesis test, not a proven cause from reversing. It asks whether RP2 remains electrically available long enough for the endpoint to appear.