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[Thomas DeBellis]

Funny you should say that; I went from Tops-20 systems programming to 
embedded systems development for 4 or 5 years.

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.

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.

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.

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.

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...

Every time I think about getting back into embedded systems, I think 
about the 9516 and ... think about doing something else.

> ------------------------------------------------------------------------
> 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.
>> ------------------------------------------------------------------------
>> 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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