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

From: J.C.Wren <jcwren_at_jcwren.com>
Date: Thu Feb 13 00:41:00 2003

        I always liked the 6809. I had a small FLEX system for a while that was
fun. But sadly, Motorola managed to blow their own head off with the 6809,
compared to the market share it could have had. "OK, 6809s are available
this quarter. The 6809e will be next quarter. Oh yea, and three quarters
out is the 68000." Only a small percentage of the market didn't wait.
Especially after the 68000 as a microcode core was validated by GM buying up
so much of the production.

        According to friend of mine that worked at IBM, the 6809 was a serious
candidate for the what became the PC (remember that the original PC had a
projected market-life of 1 year, and the IBM was getting out of that fad).
What drove the the PC to use the 8088 was the fact that they had 10 Intel
blueboxes sitting around from the DisplayWriter. Since the PC was to some
extent a non-officially sanctioned project, they elected to use the tools on
hand, rather than purchase Exorcisor development systems. The rest was
history (and my friend has serial #0001 of the PC Jr, and the first 5MB HD.
He also was the developer of the PC Jr. speech system. Another buddy was
the lead architect on the VGA. Did you know that approximately 30% of the
logic in the VGA was put there because it was on the CGA and no-one knew
what it did? And management wanted the lowest compatibility risk path.)

        Somewhere, I even still have a small 6809e system I point-to-pointed on a
piece of that gawd-awful Radio Shack phenolic board with the single side
copper pads. I think it has a modified MikBug monitor on it.

        --John


> -----Original Message-----
> From: cctalk-admin_at_classiccmp.org
> [mailto:cctalk-admin_at_classiccmp.org]On
> Behalf Of Stuart Johnson
> Sent: Thursday, February 13, 2003 01:14
> To: cctalk_at_classiccmp.org
> Subject: Re: Virtual vs Physical memory (was Re: Designing
> around a 6502
> )
>
>
> ----- Original Message -----
> From: "ben franchuk" <bfranchuk_at_jetnet.ab.ca>
> To: <cctalk_at_classiccmp.org>
> 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 - 00:41:00 GMT