Virtual vs Physical memory (was Re: Designing around a 6502 )

From: Stuart Johnson <>
Date: Thu Feb 13 00:16:00 2003

----- Original Message -----
From: "ben franchuk" <>
To: <>
Sent: Wednesday, February 12, 2003 4:29 PM
Subject: Re: Virtual vs Physical memory (was Re: Designing around a 6502 )

> Roger Merchberger wrote:
> > So where would that put the Hitachi 63C09? It's 6809 compatible, but in
> > 6309 mode, it has 4 8-bit registers, combinable to 2 16-bit registers
> > that you can do full 16-bit arithmetic on... but wait! There's More! No,
> > not Ginsu Knives.....
> Having brought the subject up, I tend to think the 6809 is a 16 bit cpu
> because of the good addressing modes and the Intel 8086 a 8 bit cpu
> because of the lack of them. Also OS/9 for the 6809 was very
> nice system. Ben.

I suppose then that the 8080 is a 16 bit computer because the HL register
pair could be used as a 16 bit pointer?

I am a LONG time programmer & system builder and what opinions I have were
developed on my own - through experience. Your mileage may vary.

One criteria you may have overlooked regarding the designation of a computer
as 8, 16, or other width is how wide is the memory bus? For the 6809, 6502,
8080, etc., the memory width is 8 bits.

Also, I didn't say that the 6809 and related chips weren't useful or good
chips - just that in my opinion (and the manufacturers as well), the 6809
was an 8 bit chip. There were some nice systems built using it; including
one I hand made for a friend. I think he ran FLEX on it.

Stuart Johnson
Received on Thu Feb 13 2003 - 00:16:00 GMT

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