7 Mar
2021
7 Mar
'21
2 p.m.
On Mar 5, 2021, at 9:02 PM, Johnny Billquist <bqt
at softjar.se> wrote:
On 2021-03-06 02:33, Paul Koning wrote:
DDCMP runs fairly well on RSTS with the printer port at 9600, but I get some overruns. My
guess is that the terminal driver (which is front ending the DDCMP machinery) isn't as
lightweight as the equivalent on RSX. Or do you bypass the terminal driver and get a
separate comms-specific driver for this case?
> ...
I would have liked better comms. The USART has
such a tiny FIFO that you can't run it at higher than 9600 bps even with the J-11 CPU.
At least not with RSTS; perhaps a lighter weight OS can do better. The printer port is
worse, that one can't run DDCMP reliably at more than 4800 bps. I normally run DDCMP
on the PC3XC, which is a 4-line serial card that uses two dual UART chips (2681?) with
reasonable FIFO.
Hmm. I'm pretty sure I was running my -380 with the printer port for DDCMP on HECnet
for a while, and at 9600 bps. But with P/OS, you are not using the console port as
such. That's all on the graphics side.
But unless I'm confused, that's the same port. The printer port just can also be
the console port, if you short pins 8-9, right? Except it won't fully work the same as
the DL11, since interrupts work differently. But polled I/O will work the same.
But I would expect the speed characteristics to be the same for the console as for the
printer port.
Correct, printer and console are actually the same thing. If you use the console cable
(pin 8 connected to 9) then that materializes a DL11-like CSR set at 177560. Yes, with
polled I/O such as the ODT microcode uses that works just like a real DL11, but for
interrupts it's different. In RSTS, either way that port becomes a terminal port.
RSTS does have support for the graphics module, in "glass TTY" mode within the
initialization code and full VT220 emulation in RSTS proper. Well, except for blink mode,
and no bold in 132 column mode.
paul