[ddon]

Recently found Z80 video of how a guy makes ZX Spectrum computer from ground up, fixes bugs and problems as he proceeds. Video is in Russian, but still amazing even if you don't understand it!

https://www.youtube.com/watch?v=8rWCYo1UcOQ

[jdmoreira]

A lot of the ZX Spectrum functionality and logic is in the ULA, an ASIC.

There's a whole book on the ULA - http://www.zxdesign.info/book/theZXSpectrumULA.shtml

[dfox]

Actually there is now design out of 74ls series logic that replicates functionality of the ULA (it is probably completely bug-for-bug compatible), IIRC it was designed by author of said book.

[XtalJ]

Nice, I'm thinking about making it possible to connect it directly to a display/TV and keyboard. Now, I have to have a terminal or laptop + terminal emulator.

[jdmoreira]

It seems hard to drive a vga display without resorting to fpgas or an avr.

If composite is enough, the NES PPU could be a fun addition to that design :)

[Rhinobird]

Apparently, it can be done with a bunch of TTL logic chips.

http://forum.6502.org/viewtopic.php?f=4&t=3329

[XtalJ]

Yes, the composite solutions sounds more fun :-)

[ddingus]

A Propeller Chip does this easily.