Brent Hilpert wrote:
Just rumour to me, but circa 1980 when I was doing some software development
with the spanky new 68000, I was told that the 68000 had been prototyped
as (literally) a large wall of SSI/MSI logic.
Billy responds:
That was pretty much the modus operandi on early MSI/LSI chips. All of the
early ASIC's I worked with were bread boarded from SSI or even single gate
ICs. The vendors would provide design kits with lots of these little chips.
Most of them were 4 or 8 pins; a few were 14 or 16 pins. You can still buy
them today to patch bugs on LSI until you can roll the metal. First ones
were TTL, then they moved to CMOS. I even remember one ASIC that we used
ECL gates on.
This was in the early 80's. Gradually, the design software caught up and
you could simulate your design on a computer. It's hard to remember that in
the days before PCs, many of tools we take for granted, didn't exist. For
example, when CDC was designing the Star series and the ETA machines, the
early design automation consisted of huge programs to lay out the logic.
The designer input the logic equations on decks of cards. I remember seeing
some of these early programs taking 20-40 hours to run, with card decks of
thousands of cards.
I think I have a few of these early proto boards left. They would make a
great display on the progress in the industry. We used a 12" by 24" size
and interconnected them with ribbon cable. I never saw a wall mounted unit.
But we had many that covered a standard workbench top and they later fit
into a 24 pin package.
Billy