Welcome and VME

From: Dwight Elvey <elvey_at_hal.com>
Date: Tue Nov 14 14:38:16 2000

ard_at_p850ug1.demon.co.uk (Tony Duell) wrote:
> >
> > Tony Duell skrev:
> >
> > >> I don't think I could form any relationship to a 4-bitter, either. I
> woul=
> >
> > >Oh, there are a lot of them about. Of course it depends what you mean by
> > >'4 bit', but if that's the ALU/bus width, then the HP Saturn processor
> (used
> > >in the 71B, 28, 48, 49, etc, etc, etc) is a 4 bit chip. And I certainly
> like
> > >those machines (and yes, IMHO they are computers rather than calculators).
> >
> > I have no idea what you're on about. =)
>
> Just about every HP calculator since the HP71B has been based on a CPU
> called the Saturn (OK, the HP6S and HP30S aren't). This chip has a 4 bit
> ALU and external bus, but with 64 bit data registers and a 20 bit address
> width.
>
> > Besides, a 4-bit address bus seems utterly, utterly limited.
>
>
> Who said anything about a 4 bit address? Address width != ALU width in
> general...
> The Saturn works with 20 bit addresses. Memory is 4 bits wide, so the
> Saturn can address 1Mnybbles (or 512K bytes). Some modern machines
> (HP49G, for example) have bank-switching hardware to extend this further.

Hi
 We all agree that the i4004 was a 4 bit machine. It had
a 12 bit address on a 4 bit bus that sounds similar to the
HP one. The 4004 used register pairs, that doesn't make
it a 8 bit machine. It also used 8 bit instructions.
 The bus does not define that it is a 4 bit machine. The width
of the ALU does. Not the instruction width and not the address
size or register size.
 I agree with Tony.
IMHO
Dwight
Received on Tue Nov 14 2000 - 14:38:16 GMT

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