1) If you are looking for a specific motherboard, please understand that for the most part, 486 motherboards are obsolete and out of production by all the major manufacturers.
2) IF you need help to identify a motherboard this can usually be accomplished by getting the BIOS number from the first boot up screen (the screen where the memory counts down). You can go to these web pages for more information:
For AMI BIOS motherboards: www.wimsbios.com/numbersami.shtml For Award BIOS motherboards: www.wimsbios.com/numbers.shtml
3) Once you have identified the motherboard's manufacturer, you can go to their web-site for support. Sometimes they have updated (BIOS) files that can be downloaded and the latest manuals for that particular board.
4) Motherboard manufacturers come and go, and if you can find the one you need on line; you may be disappointed to find out that your board is no longer supported. In that case the best that can be done is to email their tech support.