LGA 1155 (Socket H2), supporting Sandy Bridge and some Ivy Bridge processors.
Based on hardware listings for boards carrying this marking, the primary technical specifications include: intel desktop board 21 b6 e1 e2 specification link
Intel has discontinued its "Desktop Board" product line and has moved many documentation assets. To find the exact specification for your specific board version: LGA 1155 (Socket H2), supporting Sandy Bridge and
If the official Intel link is archived, sites like eBay often list detailed physical specs for these used boards. Technical Troubleshooting & Drivers LGA 1155 (Socket H2)
If the board fails to POST, check for BIOS version compatibility, especially when using 3rd Gen Intel CPUs on older 2nd Gen boards.