Well, FPGAs use SRAM-based look-up tables to do their combinational
logic functions - so not that crazy - if it works and gives good enough
results for the task at hand, people will find ways of using the
technique. But I imagine there were a host of other things that weren't
done as well as possible that added up to 8 hours vs. 3 minutes.
On 01/15/2023 12:09 PM, ron minnich wrote:
I just stumbled across an old letter, from a VP of
Burroughs to me and
Steve Bartels, authorizing $30,000 for a port of Unix to the E-mode
stack machine. I had forgotten getting it.
Burroughs was famed for its stack machines. E-mode was a kind of last
gasp attempt to save the stack architecture, which failed as far as I
know, see this table:
http://jack.hoa.org/hoajaa/Burr126b.html
I worked as a hardware engineer on the A15. I also had been a Unix
user for 7 years at that point and kept pointing out how awful the
Burroughs CANDE time-sharing system was, and how much better Unix was.
At some point I guess they asked me to put up or shut up. I got that
money, and left Burroughs a week later for grad school.
Funny note: A15 was Motorola ECL (MECL), and ran at 16 Mhz.,
considered fast at that time. We used a technique called "stored
logic" which was, believe it or not, using MECL RAM to map logic
inputs to outputs, i.e. implement combinational logic with SRAM. Kind
of nuts, but it worked at the time. We also used a precursor of JTAG
to scan it in. Those of you who know JTAG have some idea of how fun
this had to be.
One side effect of working with MECL is you realized just how well
designed the TI 7400 SSI/MSI parts were ... MECL always just felt like
an awkward family to design with.
Another funny story, pointing to what was about to happen to
Burroughs. We had an app that ran for hours on the stack machine. We
quick ported it to a VAX, started it up, and headed out to lunch --
"this will take a while, let's go eat." We got to the front door and:
"Oh, wait, let me hop back into the office,I forgot my jacket". And,
noticed, the program was done in ... about 3 minutes. Not 8 hours.
That's when we knew it was game over for Burroughs.
If a picture of this letter would be useful in some archive somewhere,
let me know, I can send it.