[coreboot] 486 Motherboard from scratch

Rudolf Marek r.marek at assembler.cz
Fri Nov 23 10:57:20 CET 2012

> How hard would it be to design, source components and construct a
> motherboard for something simple such as a 486DX from scratch?

I'm the software guy but, I think you don't need the chipset, maybe 80386SX with 
static ram aka 62512 and some simple decoders would be good choice. For dynamic 
RAM you would need some controller. For the "legacy" PC i think you need to 

8042 - keyboard + extra bits
8253/8254 - Timer
8259 - Interrupt controller
8237 - Possibly you might need DMA controller if you want to use floppy etc

Maybe doing this in some CPLD/FPGA would also be an option.

For the bus, I would choose ISA...

80386SX has 16bit bus so not so many wires. Sufficiently low clocks.


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