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Re: MISC




> >Well - if you look at them closely it becomes obvious that
> >the six machines are after all just flavours of two ideas.
> >
> >1) The move machine
> >2) subtract, branch
> >
> >The mentioned "subtract" machine is a combination of both.
> >
> >However I dont really consider 1) as a one instruction machine.
> >After all it is just a fancy way of doing microcoding. A move
> >to the PC is after all not just a move, but a JMP. And thus
> >you already have two instructions. The same goes for the ALU
> >stuff.
> 
> Bear in mind that the PC doesn't have to be an actual register. A good
> example of this is the PDP-5, which stored the PC in location 0.
> Executing an instruction began by fetching location 0 and using it as
> the address of the instruction to be executed. It was possible for a
> DMA device to cause a jump by writing to location 0; this was, in fact,
> how the front panel loaded an address into the PC.

Yeah. Thats how the move machine works. It doesnt have real registers.
Everything is memory mapped including PC, ALU etc.