Jerome Fine (jhfinedp3k at compsys.to) wrote:
How would device drivers designed for a Qbus or Unibus do disk I/O?
How would serial ports to a terminal operate?
This is the killer with the S-100 plan. I've got a bag of T-11 chips and
had considered doing something like the SBC6120 for a PDP-11, but it's
pointless unless all the peripherals are also PDP-11 compatible. Unless, of
course, you have lots of time on your hands and want to write your own
PDP-11 OS and tools, and that'd take an order of magnitude more time than
designing the hardware.
You could, if you had the right bits and knew enough about RT11, just
write new device drivers for RT11 and port it to S100 hardware. I'm sure
there are people with enough knowledge to do that, but RT11 is _not free_.
What hobbyists do in their garage is one thing, but any commercial endeavor
would have to be careful about putting their name on that.
AFAIK there are no "free" OSes that will run on a T11. 2bsd is your only
option, and that'll need at least an F11 CPU. An F11 S-100 card would be a
cool project (I'd buy one!) but it'd be much harder. F11s are a multi-chip
chipset, much less well documented at the hardware pin level, and less
available than T11s.
There's always the FPGA route, but then the S100 becomes superfluous. You
could fit a whole 11/73, including all the peripherals, into any modern FPGA
without even trying and all you'd need beyond that are the connectors and
level shifters.
Bob