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.

Later

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