> I built a programmable 8-bit computer from scratch on breadboards using only simple logic gates.
Sorry, but this is slightly incorrect. First, he is using ready-made adders in ALU which are not "simple logic gates", second he seems to use ROM in control logic which replaces tens or hundreds of logic gates one has to use of they don't have a ROM and a programmer.
If I was building a CPU, I would make 1-bit ALU and shift data bit-by-bit to save ICs because 1-bit ALU requires 4-5 simple ICs and 8-bit ALU would require 8 times more and that's too much.
Next, I would use 4-bit registers instead of 8-bit because 8-bit register requires 2 ICs and 4-bit register can be implemented with one IC. Also it allows to reduce the number of wires and amount of work to connect them. This makes CPU slower though because it has to access memory twice as often.
Also I was surprised to read in comments that in some universities students are designing CPUs as a practical project. Must be interesting.
Translation: I like to crap on other peoples accomplishments. I don't realize that adders are simple logic gates for the people who were actually there when 7400 TTL was a new thing and building ALUs out of adders is one of the oldest ways of building them (unlike "cheating" using a 74181, for example). Or that using PROMs to replace logic is just as old. I propose my "better" way of doing things that unlike the OP I'll never actually do, but I get to crap on him. I'm so disconnected from reality (or went to such a low grade school) I don't know that people actually learn how to build CPUs in school, as opposed to this knowledge being imparted from mystical higher beings directly into CPU architects skulls, or some such.
But mostly, I like to crap on other peoples accomplishments.
> I built a programmable 8-bit computer from scratch on breadboards using only simple logic gates.
Sorry, but this is slightly incorrect. First, he is using ready-made adders in ALU which are not "simple logic gates", second he seems to use ROM in control logic which replaces tens or hundreds of logic gates one has to use of they don't have a ROM and a programmer.
If I was building a CPU, I would make 1-bit ALU and shift data bit-by-bit to save ICs because 1-bit ALU requires 4-5 simple ICs and 8-bit ALU would require 8 times more and that's too much.
Next, I would use 4-bit registers instead of 8-bit because 8-bit register requires 2 ICs and 4-bit register can be implemented with one IC. Also it allows to reduce the number of wires and amount of work to connect them. This makes CPU slower though because it has to access memory twice as often.
Also I was surprised to read in comments that in some universities students are designing CPUs as a practical project. Must be interesting.