Generic PEX88048 cards may ship with misconfigured EEPROM (Gen1 x4 upstream)

A user reports that a "henryreal"-branded Broadcom PEX88048 PCIe switch card bought on Amazon for about $240 shipped with an EEPROM misconfiguration that advertises Gen 1 x4 (2.5GT/s) as its maximum upstream link capability instead of the chip's Gen4 x16, causing zero GPUs to appear on any downstream port. The card enumerates as Broadcom PEX880xx [1000:c012] and its downstream ports also report only 2.5GT/s capability, while a correctly programmed card should show 16GT/s at x16 in LnkCap. The user advises buyers of PEX88048/88096 boards for GPU use to run lspci -vv on the upstream port before building around the card and to return it if LnkCap shows 2.5GT/s, noting there is no user-serviceable fix without Broadcom's proprietary SDK tools.

Due to frustration, claude is responsible for this document. I bought a “henryreal” branded PEX88048 card from Amazon ~$240 . It enumerates as a Broadcom PEX880xx 1000:c012 , the switch topology appears in lspci -tv , fans spin on both R9700s power through C-Payne device adapters is fine — but zero GPUs appear on any downstream port. The root cause is in the upstream port’s capability register: === 01:00.0 upstream port === LnkCap: Port 0, Speed 2.5GT/s, Width x4 LnkSta: Speed 2.5GT/s, Width x4 LnkCap2: Supported Link Speeds: 2.5GT/s This is a Gen 4 switch chip advertising Gen 1 x4 as its maximum capability. That’s not a negotiation failure — it’s the EEPROM configuration. The chip can do Gen4 x16, but the board’s EEPROM tells it not to. All downstream ports also show 2.5GT/s capability only. For comparison, a working card should show Speed 16GT/s, Width x16 in LnkCap. Upstream port === 01:00.0 === LnkCap: Port 0, Speed 2.5GT/s, Width x4, ASPM L1, Exit Latency L1 <32us LnkSta: Speed 2.5GT/s, Width x4 Downstream ports all empty — no GPUs detected === 02:00.0 === LnkCap: Port 224, Speed 2.5GT/s, Width x16, ASPM L0s L1 LnkSta: Speed 2.5GT/s, Width x16 === 02:04.0 === LnkCap: Port 225, Speed 2.5GT/s, Width x16, ASPM L0s L1 LnkSta: Speed 2.5GT/s, Width x16 === 02:0c.0 === LnkCap: Port 227, Speed 2.5GT/s, Width x16, ASPM L0s L1 LnkSta: Speed 2.5GT/s, Width x16 === 02:1c.0 === LnkCap: Port 255, Speed 2.5GT/s, Width x16, ASPM L0s L1 LnkSta: Speed 2.5GT/s, Width x16 - Card is physically x16 edge connector, fully seated in CPU-direct Slot 1 X870E Tomahawk, Gen5 capable - Reseated the card, tried BIOS slot speed at Gen4 and Auto — no change - No DIP switches on the board to change upstream config - GPUs have power fans spin from C-Payne 6-pin slot power + 12VHPWR from PSU - pci=realloc in GRUB, Above 4G + ReBAR enabled in BIOS - Vendor website unreachable, no firmware download path Not all PEX88048 carrier boards ship with correct EEPROM programming. The Broadcom chip is fine — the board vendor’s firmware is wrong. There’s no user-serviceable fix without Broadcom’s proprietary SDK tools. If you’re buying a PEX88048/88096 for GPU use, run lspci -vv on the upstream port before building anything around it. LnkCap should show 16GT/s Gen4 and your expected width. If it shows 2.5GT/s, return it. - ASRock X870E Tomahawk MAX, Ryzen 9 9900X, 96GB DDR5 - 2× Radeon AI PRO R9700 gfx1201 on C-Payne SlimSAS Gen4 device adapters - Ubuntu 24.04.4, kernel 6.17 HWE, ROCm 7.2.3 - Goal: dual-card DDP/FSDP training via RCCL Hi Waylon, I saw your work with the PEX88048 EEPROM configuration. Have you done any work with PEX89000/PEX89144 Gen5 switches? I’m looking at repurposing Dell XE9680 PEX89144 switch boards and would appreciate any advice or issues you think I should watch for.