I dislike using the word "build" I prefer assemble. Going by that, yes I have fully assembled computers before. It's actually not that hard, you just have to make sure all your parts will get along. Is this RAM card supported by your motherboard. Does your power supply put out enough wattage? Just things like that.
P.S I prefer assemble over build because assemble acknowledges you're actually does just taking a bunch of parts and putting them together.
I made adders and subtracters in minecraft, I could express the same thing in real life circuitry so I think I could but Im not sure if I want to learn at that level, maybe its a good way to learn code, to work through all the levells but not sure if can be bothered, like to see my work working, you got me thinking about calculators and flip flops you rascall.
I visited my parents this weekend and my 14 year old brother showed me the 4bit ALU he designed and built in minecraft, attached to a 4 element stack, using some unconventional techniques for what an ALU does, but still really clever. It's 4 bits because the max length of a redstone circuit without any repeaters is 16 squares, and he uses pistons to extend or shorten the redstone circuit based. He looked up nothing for it, well other than logic gate stuff. But I taught him a bit about logic gates when he was 11 or so.
Yes, I am aspiring to study Computer Engineering in a couple of years (Electrical Engineering/Computer Science Hybrid) and have been studying the architecture of the Intel 8085 microprocessor, along with a few online lectures, studying of various IS/manufacturers manuals, and just teaching myself.
I am currently in the process of designing a 20 pin 6 bit CPU, though I am probably not going to physically construct it as of now. It should have a 6 bit MAR, 6 bit MDR, 6 bit instruction pointer, and 6 control lines for the reading and writing of 6 bit data/addresses (multiplexing is overambitious to me). I will use a 9V secondary battery as a power source (resistor will limit potential difference to +5V) and the current will flow through the 20th pin. Due to my limitation of control lines; there will be, much like the intel 8085, and Address Latch Enable control line to inform external devices and the processor itself the type of information it is receiving. I have yet to figure out the design of the coordinating part of them timing and control unit, so I do not know the estimated frequency yet.
My ALU will be able to perform addition and subtraction, along with a few Boolean logic calculations.
I will use standard LEDs to output raw binary though in the future I am thinking of expanding data bus width to write 1 bit data for a small GPU to process (black and white pixels), since colour would require me dealing with analogue currents.
Of course, since I was silly enough to choose 6 bit, I would have to design the RAM as well, which would be static.