[Milsurplus] IBM PC

[Brooke Clarke]

Hi Ray:

I still have my South West Technical Products (SWTP) computer.  Things 
that made it different from the IMSI are:

*  no front panel address and data switches for loading the boot 
program, only power and reset switches.  The Motorola 6800 processor 
booted from a ROM.

*  uses two busses on the mother board, one for the main boards such as 
CPU, RAM, DMA (yes Direct Memory Access was needed since the 6800 was 
not fast enough to bit bang data to and from 8" floppy drives.) and a 
small buss that had the address decoded from the main address buss, this 
way each I/O board did not need to decode the full address buss, making 
it very easy to roll your own I/O.  This may have been the first home 
type interface buss?

* I replaced the stock boot ROM with one from Microware that contained a 
Real Time Operating system, which was possible with the Motorola 6800 
because it supported writing code that was relocatable, recursive, 
relocatable, and more "R" words I now forget.  This was not possible 
with the Intel chips where all code needed to be written for a specific 
address location.  This flexibility with the Motorola chips was improved 
with the 6809 used in the Radio Shack Color Computer and later in the 
68000 series chips

I remember the first HP automatic network analyzer used the HP 2116 with 
core memory.  The neat thing about core memory is that there is no 
booting.  You turn on the power and the program is running, you turn off 
the power and the program stops wherever it is.  I understand that there 
is a major effort to develop MRAM (Magnetic RAM) so that modern 
computers can have the advantage of a memory that does not forget when 
it looses power.

Have Fun,

Brooke Clarke, N6GCE

-- 
w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
http://www.precisionclock.com



Date: Thu, 16 Sep 2004 12:33:21 -0400
From: "Ray Fantini" <RAFANTINI at salisbury.edu>
Subject: [Milsurplus] IBM PC
To: <milsurplus at mailman.qth.net>
Message-ID: <s1498815.000 at mail2.salisbury.edu>
Content-Type: text/plain; charset=US-ASCII

All evolutionary process have steps, the modern desktop PC did not
evolve from one thing but is a conglomeration of many things, including
the old Alter, Hellos systems, the many signal board CPU kits, anyone
remember the Kim? And keyboard based systems like the Apple and Pet with
the 6502 and the TRS-80 and others built around the Intel chip, I had a
8080 based S-100 system that ran CPM and would love to know where it is
today. And I do not discount all the relevance of the other systems but
still stand by my statement that the IBM fifty one hundred series, the
PC and later XT is the turning point and the start of the modern desktop
era. The IBM was the first to use an ISA backplane, yea I know it's a
copy of the idea that Apple used in their twos but everyone else used it
afterwards. The IBM had DOS, ok so it's a Microsoft reverse engineered
version of CPM, but once again everyone else used it, well except for
Mac people. And IBM had a disk drive, thus the need for DOS where the
TRS-80 and most systems before it used a cassette and the old basic load
and save commands for peripheral management. Myself I have not seen but
was told a PC could be bought without a floppy drive and used with just
the in ROM basic and a cassette deck but have never seen that.
If the ARC-5 is relevant for being the first modern style aviation
radio, and showing the direction of radio evolution at that time, I
stand by my assertion that the IBM PC also showed the way the future
will be. Not to mention another analogy can be drawn by the fact that
with both by the time they were in full production they were already
obsolete.
Of course the next question is was the ARC-5 really that significant in
comparison with radios like the airborne VHF SCR 511 sets or ARC-3
produced a little later? Or just a technological blind alley that
finally ended with the little gray ARC radios. 
Ray Fantini KA3EKH