8-Bit CPU's have a datapath 8 bits wide and as a result can do a lot more than their 4-Bit siblings. Many early computers like the Commodore Vic 20 and Commodore 64 used simple 8-Bit CPU's.
I just got a tip about the PJ5 TTL CPU project and had a loook at their build log. This is a really cool project with a ton of thought. I highly recommend having a look. It appears to me that they are running their machine faster than they originaly anticipated and they're not using microcode with a goal of one clock cycle per instruction rather than bouncing an instruction to ROM and back again taking up precious cycles to complete. Really cool project.
Ok, this is cool. I haven't seen this one until now (June/2014) but it appears to be a TTL CPU project that was undertaken in 2004. I've only briefly looked at the project but it looks well documented and very complete including schematics and downloadable tools.
A computer made out of nothing but NAND gates. Everything is NAND gates right down to the 7-seg display drivers and to conserve gates, he built a 1-bit ALU which operates on 8-bit registers 1 bit at a time. Very cool project.
Updated with link to Jack's new website This is the same guy from above with his 8-Bit computer which uses a standard keyboard for input and also has a scratchbuilt video card to output B/W video.
This homebrew TTL CPU is pretty cool. Dennis Kuschel, the originator/inventor offers it as a kit. The computer kit can be configured from minimalist to expanded and runs several packages of software including an open source "window" based operating system called Contiki. If I wasn't having so much fun tinkering with my own ideas for a TTL CPU, I might consider building one of these.
This is probably the most well known scratchbuilt TTL CPU in existence. I've put it under 8-Bit CPU's because although it supports internal 16 bit ALU functions, from my shallow understanding of its architecture, it fits the description of an 8-Bit computer. It's a pretty impressive machine!
I've checked this site out quite a bit over the years. There's a lot of really good information about control logic, control bus routing and timing considerations. Even if you choose a different approach, this is good info to have.
