I’ve been playing with the idea of designing and maybe actually building a stack processor (that is, a processor that, rather than a bunch of registers, has a data stack as its primary local data storage), using 7400-series and similar ICs. Obviously this is not practical in the least, but it could be quite fun.
The idea is to use discrete ICs to implement every aspect of the processor, like so:
– 4x 74181 chips would form a 16-bit ALU
– a 16-bit register would form the top-of-stack (TOS) register
– a 64K dual-port SRAM would be the memory (dual-port so that both data and instructions can be read simultaneously) – this would include instruction memory, the stack itself, and data memory.
– a 16-bit binary counter to implement the PC
– a serial EEPROM for the BIOS
– some random peripherals – some 7-segment LEDs, a UART, maybe an LCD
– a shitload of gates to implement the control unit/address decoding
Madness.