Instead of searching for the erroneous "Intel Desktop Board 21 B6 E1 E2 Manual," use these direct sources:

: For older boards, refer to general Integration Guides which cover standard assembly for this era of hardware.

Intel has retired support for many legacy boards, but the manuals are archived at:

found on several Intel Desktop Boards from the early 2010s, specifically those using the Intel 7 Series Chipset (LGA1155 socket)