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<p>Funny you should say that; I went from Tops-20 systems
programming to embedded systems development for 4 or 5 years.</p>
<p>If you Google the ProDisk-464, you can see the system I worked
on. I designed a high speed crash proof file system specifically
for multi-channel audio recording in 1989 and worked on it until
91 or 92.</p>
<p>The system had a time division multiplex bus which would allow up
to 64 channels of audio, which nobody was doing in the digital
realm, back then. The audio was split up to storage units (or
SU's) where my code ran. Each SU could handle four channels of
sound and was running my operating system in 80286 protected mode.</p>
<p>Despite what Bill Gates says, I loved that processor. It was
finicky about selector usage and length and wrung a lot of bugs
out. The user interface was on a Mac, partly written in C.
Sometimes to find bugs that, I would cross compile it and run it
on the 286.<br>
</p>
<div class="moz-cite-prefix">Every so often, I had to tweak things
into assembler to meet the real time requirements. The only
problem was an AMD 9516 DMA controller that we used. It was very
nice, being able to execute short channel programs. This worked
well almost all the time; in fact, it was pretty wonderful--a lot
easier than an RH20.<br>
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<div class="moz-cite-prefix">And along came the extreme cases; since
it was reading its channel program from the same memory that was
being DMA'd to, for very short transfers (like a few words), you
could blow it completely and not get to the interrupt in time.
Bad... Very audible. The solution really broke my heart; I had
to toss all my fine interrupt and channel building code and sit in
a tiny loop polling. Ugh...</div>
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<p>Every time I think about getting back into embedded systems, I
think about the 9516 and ... think about doing something else.<br>
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<pre class="moz-quote-pre" wrap="">On 4/24/20 12:17 AM, Dave McGuire wrote:
Those days are long past for me. ;) Years ago, I moved entirely into
embedded systems development, where I can reasonably (and indeed, am
expected to) spend a whole day optimizing out a few cycles or a few
bytes. I still do my own systems and network engineering, and
occasionally for others, but I don't like to make a living at it anymore.
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<pre class="moz-quote-pre" wrap="">On 4/23/20 10:14 PM, Thomas DeBellis wrote:
For me, not only is the miracle that Dave can resurrect these monsters
decades after they were in service, but that somehow he appears to enjoy
doing it. Maybe it's due in part that he doesn't have a couple hundred
livid angry users making the phone glow red.
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