|Page 21 of the PDF on the first page of the first link above, states that manual is also for the 5100. Look for yourself.|
When a motherboard manufacturer makes an OEM board they may not create a manual for it.
The second link above is for a sold 5100 but shows a picture of the board along with the specs.
What is it you need from the manual. OEM boards will have very few options in the BIOS settings, if that is what you are looking for.