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

> Source: <https://forum.level1techs.com/t/generic-pex88048-cards-may-ship-with-misconfigured-eeprom-gen1-x4-upstream/251129#post_2>
> Published: 2026-10-02 06:46:22+00:00

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.