Everyone has at least a couple of old 486 motherboards lying around in the closet. But what good are they?! Well, they make an excellent source of components for your hardware projects that you might otherwise have to buy, shock horror!

What can be found on a motherboard? Well...

• DRAM chips, usually 1M x 4 bit (ie 2^20 words, each word being 4 bits);
• Static RAM cache chips, usually 32k x 8 (256k bits);
• Octal tri-state buffers, quad line drivers & receivers and so forth;
• Random crystals and occasionally a crystal oscillator,
• Miscellaneous but interesting devices such keyboard & mouse controllers, floppy disk controllers, real time clocks and so forth.

Identifying Parts

The hardest part of salvaging components from old computer motherboards would be identifying what you're looking at. Hence this guide!

Motorolla in their infinite wisdom decided to leave off the first few numbers of each part number when printing their chips. So a F737 is actually a 54F- or 74F737 ("transparent octal tristate latch with 3-state outputs") and a F74 is actually a 74F74 ("dual D-type positive-edge triggered flip-flop").



The part above is a 814260-70PJ – the 814260-70 is on the top line, the PJ is on the bottom and the 9432 will most likely mean it was made on the 32nd week of 1994. It's an old chip! Not sure what the TO9 is. For the curious the 814260-70PJ is a 512k DRAM chip, 70ns. PJ defines the package as a SOJ thingy.

This one is a UM61256k-15. The M appears to be some kind of logo to make us think it's super special :p It's a 32k x 8bit 15ns static RAM chip, used for the cache modules on 486's and early Pentiums. The 256k in the part name means it's a 256k-bit device, not 256k-byte. So sadly you don't have nearly as much SRAM as you though.



This little critter got the better of me: the part number is DS1489A, not P52AF as I thought. It's a quad line receiver, which I believe acts to convert voltage levels present on RS232 lines and similar to TTL compatible levels.

Useful Resources

• DataSheetArchive.com
• DigChip.com — Nice interface, need to register to view datasheets thought.
• AllDataSheet.com
• List of 7400 series ICs — to help track down devices from partial part numbers.
• And of course Google!