"Clare Snyder" wrote in message
news
On Wed, 23 Oct 2019 08:48:33 -0700, Bob La Londe
wrote:
On 10/23/2019 6:33 AM, Jim Wilkins wrote:
"Terry Coombs" wrote in message
...
On 10/23/2019 6:34 AM, Jim Wilkins wrote:
"Steve W." wrote in message
...
...
My first was a 1984 RatShack CoCo2 with ADOS, DSDD drives, and OS7
as
well as the "C" compiler - I added an e-prom burner and a composite
video output to replace the RF output. Still have it (and the 1984
MC10 portable version).
Next was a Sanyo 550 which I upgraded to IBM compatible video - but
it
could not handle enough RAM for Lotus so I built my first PC XT
clone
What did you think of the CoCo?
I was very impressed with the 6809's powerful instruction set, after
struggling to turn a homebrew wire-wrapped 8080 machine into something
resembling the IBM PC. The 8080 lacks relative jumps and is more
suited to embedded control than general purpose computing with
loadable programs. It provided good training in computer hardware
design, though.
The company was right at the leading edge of high speed memory chip
testing so I learned a lot about transmission lines and impedance
matching that helped greatly with digital radio design later at Mitre.
The memory testers were so fast that there would be three test vectors
(address & write data) travelling out within the coax between the
machine cabinet and the test head at the wafer prober, and three
results coming back. We manually trimmed the cable lengths to match
their propagation delays within a few picoseconds, 16ths of an inch at
the speed of light.
https://en.wikipedia.org/wiki/Wafer_testing
The CoCo had an elegantly simple video controller that I borrowed, in
monochrome form, after giving up on Don Lancaster's Cheap Video.
Although I didn't use the 6809, studying it helped a lot when I had to
design a 16-bit A/D converter board to go in a 68000-based NuBus
Macintosh and the Apple Certified Programmer assigned to write its
driver quit.
I could program UVPROMs on the Automatic Test Equipment we were
building at work, I wrote a routine to do it quickly for practice, but
the engineers gave me slow, pre-production samples of 2816 flash
memory that's pin-compatible with the 2716 UV PROM, and the 6116 CMOS
static RAM I was using.
http://cva.stanford.edu/classes/cs99...ts/at28c16.pdf