Industrial Automation, MRO, Office/Business Desktops. Chipset: Typically Intel Q67 Express.
To find the correct specification for your board, you need the (Altered Assembly), which is a small barcode label found on the motherboard itself. How to Find Your Actual Specifications intel desktop board 21 b6 e1 e2 specification link
Because these markings were applied across multiple assembly lines, a board stamped with "21-B6-E1-E2" could belong to completely different generations of hardware: Industrial Automation, MRO, Office/Business Desktops
Often salvaged from standard office tower upgrades, this consumer platform natively supports 2nd and 3rd Generation Intel Core processors. you need the (Altered Assembly)
Once you have the AA number or model name, use these official Intel tools to find your specific manual and specifications: Intel S975XBX2 Workstation Board