> > Any Unix clones for 8080/Z80 systems? It ought to be doable, given that the
> > original Unix was done on a 64KB address space machine...
> The problem with any multi-tasking or multi-user system on a Z80 is that
> there is no easy way to write position-independant code. There is no
> relative call and no relative loads/stores (both the PDP11 and the 6809
> have them). There are workarounds (either you use RST instructions to
> simulate the relative call, etc or you relocate the task when you load
> it), but they make life a little harder.
Most multi user/programming atempts for Z80 systems (and
6502 which had also (long) relative jumps) I know did go
for bank switching, where the whole 64K mem, minus the
OS parts, was banked for each task - so every programm
had a fixed starting address, and a maximum mem size,
based on the bank size.
Gruss
H.
--
Ich denke, also bin ich, also gut
HRK
Received on Mon Jan 25 1999 - 09:26:54 GMT