If this code is printed on a sticker on the BIOS chip (the small 8-pin or 32-pin chip usually labeled "Winbond" or "Macronix"):
Your board is not showing all these codes at once. It is cycling through POST phases. Typically, a healthy boot will rapidly count from 01 up to FF or ER (which often means "Execute Ready" or "Error"). If the boot halts at a specific code, that is where the problem lies.
Let’s dissect each alphanumeric value. intel desktop board 01 21 b6 e1 e2 er
The coin battery (CR2032) on these boards is likely dead by now.
Intel desktop boards (discontinued since ~2013) used a combination of: If this code is printed on a sticker
Typical codes during a successful boot (from power-on to OS):
00 → 10 → 21 → 38 → 50 → 52 → 75 → 7F → FF
Your sequence 01 21 b6 e1 e2 er looks like a halted or error sequence with er possibly standing for “Error” on a 2-character LED (e.g., Er shown as Er or E2). Your board is not showing all these codes at once
Since you searched for all six codes together, you are likely experiencing one of three failure patterns: