dz-11 on a VAX-11/750 at 19,200 baud.

[Jack Jansen]

[Sorry for posting, but I couldn't reach the author by mail...]

In article <1577 at brl-smoke.ARPA> JBS%DEEP-THOUGHT at mit-eddie.arpa writes:
>
>The lost data is not really my problem though.  What I'm worried about
>is that on the console, the system spits out occasional "dz0,4: silo
>overflow."  Does anyone know what is wrong, and if so, what I can do
>to fix it?
Well, in fact you should even be grateful if it runs at 9600 baud...
The DZ is completely interrupt driven, which means that *every character*
causes an interrupt. So, 8 lines at 19.2Kb can produce an awful
amount of interrupts......
Whenever the VAX doesn't serve input interrupts in time, the input
silo fills up with unprocessed characters, and eventually some
characters will be dropped. There are two solutions:
- Set speed to 4800 baud. You will also see the performance of
  your machine jumping up, since it doesn't have to spend so much
  time on interrupt handling anymore.
- Replace the DZ by something better, probably some DH-11 clone.
  These things use DMA for output, so you get far less interrupts.
-- 
	Jack Jansen, jack at mcvax.UUCP
	The shell is my oyster.