Re: 6-bit characters (was: Re: Streams in Ada)

[Tucker Taft <stt@averstar.com>]

Marin David Condic wrote:
> ...
> I didn't get that impression. Just that "DECsystem-10" grew from "PDP-10" -
> that it was mostly a naming issue & not one of any real fundamental
> difference. There may be some technical distinction, but it seems of little
> consequence. Same processor. Same instruction set. Maybe some evolutionary
> differences, but that's true of all significant systems over time. (How long
> have you been able to buy a "Ford Thunderbird"?)
> 
> > |  PDP-20 n.     The most famous computer that never was.  {PDP-10}
> > |  computers running the {{TOPS-10}} operating system were labeled
> > |  `DECsystem-10' as a way of differentiating them from the PDP-11.
> > |  Later on, those systems running {TOPS-20} were labeled `DECSYSTEM-20'
> > |  (the block capitals being the result of a lawsuit brought against DEC
> by
> > |  Singer, which once made a computer called `system-10'), but contrary to
> > |  popular lore there was never a `PDP-20'; the only difference between
> > |  a 10 and a 20 was the operating system and the color of the paint.
> > |  Most (but not all) machines sold to run TOPS-10 were painted `Basil
> > |  Blue', whereas most TOPS-20 machines were painted `Chinese Red' (often
> > |  mistakenly called orange).
> 
> As I recall, the University of Chicago had a DECSYSTEM-20 - but I never
> actually got to touch it. What I saw of the data on it tended to indicate
> that it used the same KL-10 processor as the DECsystem-10. (KA, KI & KL were
> the iterations of the processor I remember.)

The major difference between the DECSystem-20 
and the DECSystem-10 had to do with memory management.
The DECSystem-20 had a better virtual memory
capability than the '10.  Tops-20, the operating system
for the '20, was based on the "Tenex" operating system
developed by BBN, which also pioneered the fancier 
virtual memory hardware for the '10/'20 line.  TOPS-10
was the inspiration for the original CP/M-80 which grew
up (?) into MS-DOS and then Windows.  Tenex/Tops-20 was
the inspiration for Vax/VMS, and might be called the "CISC"
of the operating system world, where Unix/Linux is the "RISC."
It is interesting that the Tenex-Vax/VMS thread joined the
Tops10-MS-DOS thread in Windows-NT (the worst of RISC
and CISC all wrapped up in one baroque mess ;-).

> 
> MDC
> --
> Marin David Condic
> Senior Software Engineer
> Pace Micro Technology Americas    www.pacemicro.com
> Enabling the digital revolution
> e-Mail:    marin.condic@pacemicro.com
> Web:      http://www.mcondic.com/

-- 
-Tucker Taft   stt@avercom.net   http://www.averstar.com/~stt/
Chief Technology Officer, AverCom Corporation (A Titan Company) 
Burlington, MA  USA (AverCom was formerly the Commercial Division of AverStar:
http://www.averstar.com/services/ebusiness_applications.html)