Supermicro H12SSL-i & AMD Epyc 3rd Gen Issues

A few weeks, two CPUs, four different Ram Sticks, and a multimeter later — my Supermicro H12SSL-i is still just showing me "FF" and I think I finally have to accept the board is dead.

Figured it was worth a write up here encase someone can spot something I have missed before I go through fighting some guy on eBay about his DoA board he sold me.

The Problem was in the beginning I was getting POST code 16 with full ram removed all of it down to 1 stick then started getting FF. Moved that single stick to every slot still FF. The fact I had a post code other then FF before and now its not even giving me that 16 anymore makes me think its a bad Motherboard.

The Build
Mobos: Supermicro H12SSL-i (Latest Bios 3.7)
CPU: AMD EPYC 7B13 & AMD EPYC 7543P (Tested using both)
Ram: OWC 128GB (4x32GB) DDR4 3200MHz 2Rx4 ECC Registered RDIMM 288pin Memory RAM
PSU: 2x Supermicro PWS-1K28P-SQ 1280W & SuperMicro Power Distribution Board, PDB-PT747-4648 L76
Case: SUPERMICRO CSE-846TQ-R900B 4U
Backplane: Supermicro BPN-SAS3-846EL1  (Not even connected while testing if its working or not)

Troubleshooting Steps taken:

- Pulled the CPU, inspected the whole SP3 socket under a light for bent/missing pins — nothing
- Reseated it properly with a torque driver (14 in-lbs) did this multiple times.
- Stripped the whole thing down to bare minimum — board, CPU, one stick of RAM, nothing else plugged in
- Walked that single stick through literally every DIMM slot, A through H — FF every single time
- Grabbed a second, completely different RAM stick and did the same slot walk — same result
- Double, triple checked both CPU EPS power connectors were seated
- Cleared CMOS
- Confirmed I was already on the latest BIOS (3.7)

At that point I figured the RAM and BIOS were about as ruled out as they could be, so I went digging in the BMC.

Health event log had nothing useful, just power-on and LAN link events. But the live Sensor Readings page, checked (while the system was on and fans spinning), showed literally everything as N/A — CPU temp, VRM temps, DIMM temps, and even the basic board rails like 12V/5VCC/3.3VCC. Also noticed the BMC's saved hardware inventory listed a CPU and RAM that weren't even what I had installed, which I'm guessing is just stale data from whoever last got this thing to actually complete a POST, way before it was mine.

That board rails showing N/A thing bugged me enough that I broke out a multimeter and backprobed the 24-pin and both CPU EPS connectors directly, bypassing the BMC entirely. Every rail measured exactly where it should be — 12V, 5V, 3.3V, all in spec. So the power is genuinely fine, the board's own sensor hub is just... not seeing it.

Since my original CPU was a 7B13 (an OEM/hyperscaler-only Milan SKU, probably pulled from a decommissioned cloud server), I couldn't fully rule out that it was PSB-locked to some other vendor's firmware — which would explain a hang this early with zero real POST progress. So I picked up a proper retail, non-locked EPYC 7543P to test with.

Same result. FF. Every time.

Unless someone can show me a sign that I'm missing at this point. Board is going back to the seller. Would love to know I'm not going crazy cause this has been a stressful few weeks trying to get this working. Going to start that process tomorrow after someone tells me I'm not completely lost the thread here.

TL;DR: RAM good (tested 2 kits, every slot), CPU good (tested 2 CPUs, one guaranteed unlocked), power good (verified with a multimeter, not just the BMC), BIOS current, CMOS cleared. Board still won't post past FF. Pretty sure the motherboard itself is the actual dead part here.