Sorry I went silent all of the sudden, lost power. Dang wind storm took out the lines for a while.
I don't really know myself, I still figure my definition is pretty close. And the first three pages of Google search for "microcode meaning" seem to agree with me. But the exact definition of microcode aside, one needs to figure out the logic gates first before any such things could even be implemented.
You guys have the right idea here, hit the nail right on the head actually. This was the vision I was thinking would be the end result for such a project, only far faster/better.
In fact, it would be cool if such a attempt was simply done directly in one of these old minicomputer cases, gutted of it's original boards course. Those old systems have pretty much the perfect layout for doing exactly what is proposed in this thread. I would even bet that the PSU's of such an old system would be perfect, while not using a single IC. So yeah, A+ for this idea, I'm all for it.
Anyway, just to rehash my general overview of such a system, and how it would come together...
Step 1: Decide on a technology for the logic gates.
I like the idea of high-end RF
heterojunction bipolar transistor's in an ECL configuration for each gates inner workings. In theory, greater than 1Ghz core clock is easily possible this way because ECL can readily obtain sub nanosecond propagation delay, though word is still out on whether or not this is actually doable on a macroscopic scale. This aspect really needs the attention of a microwave engineer to define it's plausibility then do some experimenting, before such a project could continue on.
Step 2: Design logic gate and basic PCB artwork.
After step 1 is figured out, then each of the different logic gates needs basic PCB artwork made, artwork which works well at the target speed. The artwork needs to be designed with microstrip-like theory's and techniques, as reflections and proper termination are going to be of the utmost importance at this scale. Also, much care needs to be given to reducing capacitance and resistance, to improve propagation delay as much as possible.
Step 3: Design advanced logic gate architecture.
After the internals and specifics of each gate are taken care of, each gate as a whole should be designed to fit into it's neighbors in a grid like pattern such that one can just copy/paste a gates artwork to any location on a grid to ultimately create combinational logic functions. Effectively, we would want to be able to treat each gate as a whole single building block, rather than fussing over it as a collection of parts each time. One would need to know what gate inputs, outputs, and power are going to look like before this stage could be worked on. This could arguably be VERY difficult.
Step 4: Design each major computational unit.
Each computational unit would need to be divided onto a single PCB, such that one board does one function for the whole computer. For example, the ALU would probably be one board, and the instruction decode logic on another. Each unit would have connections on it's edges, some fine gauge shielded connectors for passing data to and from the rest of the system, and heavy gauge wire/connections for power. These would be implemented as "cards" where each card would be able to be built, tested, inserted, removed, and all around dealt with separately from the rest of the system. Modularity makes for easy design, diagnosis, and repair.
Step 5: Design the computers architecture.
This is where stuff like microcode, RISC/CISC, Harvard/von neumann, buss width and so forth would be discussed. Ideally, the simplest structure that reuses the most functional units for other purposes and requires the least interconnecting would be the most practical design. However, a lot of performance and usability will be determined here. If it was intended to implement/emulate a particular language, or if we want to have a FPU or not, this would be the best place to optimism these things. This is arguably where the most fun of the whole project is.
The rest is physical construction, cable routing, cooling, power, and so on and so forth.
Conclusion.
Anyway, I'm not really seeing the kind of interest in the project that would be needed for it to really take off and be serious, so sadly, the idea is probably dead. This is fine though, It's not as if I was gung-ho cowboy enthusiastic about doing this, it's just something that has been on my mind for a while. I was wondering if there was anyone else out there with similar thoughts and ideas, so I decided I would come out with what I had just to see what happened. So here are some notes to take away from this.
1: LNB's can readily process frequency's > 1Ghz using discrete transistors and no IC's. This should be just as applicable to discrete built logic gates. But this needs to be confirmed by and expert.
2: Termination and avoiding reflections are almost certainly top priority design problems for such a system. This, and the above mean a microwave circuit engineer would probably be the VIP for such a project.
3: There exists a lot of literature on exactly how to implement ECL gates and how they work, but not a whole lot on how to realize each different gate type with ECL. (OR/NOR can supposedly be used to make any gate type).
4: Old minicomputer cabinets and hardware are probably the ideal project enclosure for a hand built discrete computer. If you can get your hands one one, you would have a great start.