Bob Armstrong wrote:
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.
That is the issue writing RT compatable drivers.
The issue is the easy cpu is T11, the only OS that runs on that due to
max ram of 32KW is
RT11. RT11 is easily found and drivers are not that hard but no one has
done that.
An alternate is an OS that has a source(in C as in CP/M68) or could be
spec'd easily such as CP/M.
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.
Some things like DL11(Serial line card) compatable port are easy to do
and a quad DL
could be done and used with a TU58 (or a solidstate analog of one). I
have done that
and it runs RT out of the box on a T11. It's not S100 and fairly simple
but complete
as RT11SJ can tell.
Forget RT11FB, RSTS or RSX as they will not do well in 24KW.
Faster and more involved mass storage is harder but you have a huge
assortment of non MSCP devices to imitate. I leave out MSCP as that is a
CPU (T11) on a board to do that.
One approach is to make a DL compatable port that does not use the
serial deivce but
looks to RT like DL and has a local PIC or what not to make a SD memory
looks like a
32mb disk (RT does not use more than 32MB without LD) and if the
handshake looks
like DL then your can use the TU driver (TU58) resized for a larger
number of blocks.
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 is UNIX but that is bigger and you still ahve the device driver
issue.
I'd think something like Linux or uClinux are both possible but again
drivers.
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.
There is that.
Genrally the PDP11 on S100 is not a great scheme as the bus to be
reasonable has to be run as 16bit mode and memory has to support RMW and
that may cause havock with some dynamic cards. That and something like
the T11 is just right for a SBC with 32KW of
static ram and a DLV11J( 4 DL compatable serial ports). Add a boot/ODT
rom at 173000Q
and your set to go. That and it's less effort then trying to wedge it
into the S100 format
and bus.
Generally I did the T11 thing to see if I could but, I have a BA11VA
with a 11/23 cpu, 256KB of ram, DLV11J (4 port serial) and MRV11(boot
rom) running for the last 30 years with a TU58 and generally speaking
larger boxes are easier to do. It's more effort to build
up a Tll than find the bits to do a 11/23 in a BA32 box. I have several
other Qbus 11s
(LSI11 [x2], 11/23B[x3], 11/73) as complete systems already. I could
ahve used the falcon
(SBC21) CPU/Rom/IO card with a pair of MXV11s but the 11/23 is better
performance and has the MMU.
You have to understand RT11 and DEC pdp11 system for the above to make
sense.
Allison