Z80 Home

Systems Without Memory

And how to make it more efficient than most Memory Systems

Fourteen years ago, there was no need for memory at all. Small Z80 systems used an EPROM to store data and the Z80 registers as memory. External SRAM was expensive, and there was no need for it at small computer systems. Instead was stack calculated by hand. It worked as a high-level code interpreted by a return.

        ORG     0h

LOOP:   LD      SP,M1   ; Setup stack

        RET             ; Run at the stack

PROC1:  POP     HL      ; Get parameters

        POP     BC      ; for procedure


        RET             ; Next procedure

PROC5:  CP      A,20h   ; Check if a space

        RET     Z       ; Continue on stack if space

        LD      SP,M2   ; Else setup new stack

        RET             ; And run at the new stack

M1:     DW      proc1,v1,v2,proc1,v1,v3,proc5,...,loop

M2:     DW      proc1,v1,v8,...

A sort of high-level code was written in the stack. And the code only contained subroutines and pop's to get the parameters. Beginning was done by return.

The stack calculated by hand was an efficient way to make high-efficient programming and it was more effiecient than using call's, load and push, etc as in typical systems with memory.


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