homemade computer for fun and experience...

<IF you can stick the XT keyboard (are keyboards that talk that protocol <still being made?) then look at the circuit of the PC or XT. The keyboard <interface is a few TTL chips hung off an 8255. At keyboards can be used as well as they are similar (not the same). You'll have to make a interface as the serial is not compatable with UARTs, also you will have to convert the key down/Key up codes to something more human. <I'd make it modular (in that I'd have expansion slots), but I'd probably <put the CPU + RAM + basic I/O on the 'motherboard'. For prototyping, <DIN41612 connectors are easier than edge connectors because you don't <need special boards with the connector fingers on them. An acceptable bus is ISA-8bit and there are plenty of FDC, VIDEO, HDC cards for that bus that could easily interface to z80. <SRAM is a _lot_ easier. And now that 64K SRAM is 2 chips at most (62256's <are cheap now), I'd use that. DRAM is not too hard until you realise that <layout and decoupling are critical if you want to avoild random errors. Same comment, one proviso, if your doing over 256k consider DRAM and MMU. a good article for that is at the TCJ site. <[For the hardware wizards here : Yes you can homebrew with DRAM - I've <done it. But not as my first real project]. For a z80 system of 64 or 128k static is far easier. Also 128kx8 parts are cheap so even 256k or 512k ram systems are modest. Allison