I've been studying computer and processor design for years now, and at several points I got the idea to start a project or two, usually consisting of building my own computer or processor from discreet components.
I've played around with relays I had and made a 8 bit adding circuit, and decided I was going to make a full relay based computer. I have the knowledge of processor design required, and constructing logic gates with relays was really simple, but before I knew it, my ideas for the project became a little too ambitious. In other words, I wanted to take it further than just the basic design, and I realized the over development of this design would be wasted by the inherent limitation of the speed of the relays.
Anyway, I've though some more, and have look at similar projects. Specifically I've looked at home built computers that were created out of 74 series TTL logic ICs. Of course, I wanted to take it one step further, and built it without the use of any ICs (yes, I know, you must think I'm crazy or simply a masochist.)
The basic idea was to design and build individual component cards, each card would consist of a handful of simple logic gates (a hex inverter for example) and then these cards would then be inserted and configured accordingly. In the end, I would really simply be replacing the TTL logic ICs with comparable, home made logic cards. The design isn't too different from what you might have seen in a UNIVAC style transistor computer.
While I know the design of computers at a logic level, I'm a little bit hazy when it comes to the transistor level. My question would be, what type of transistors would be best to use, and what type of logic design? For instance, I could use BJT transistors and Resistor-Transistor logic, or I could use MOSFET transistors in a CMOS style logic. There will likely be a lot of logic gates in this. My guess is it could end up being close to a thousand or more, but possibly less.