Re: [9fans] Re: random moving of cursor arrow

["Douglas A. Gwyn" <DAGwyn@null.net>]

boyd, rounin wrote:
> iirc, from the dz-kmc days you needed to manage the 'fifo' so it wouldn't
> overrun, but at the same time you needed a timer to empty it [stick on the rawq]
> so stuff just didn't get 'stuck'.

No, the problem arises when people try to set the input alarm
threshold at more than 1 character.  In the case of the DZ11
the right thing to do was to interrupt on any incoming
character and after processing (putting in the queue) wait a
tiny bit for the FIFO to trickle down then test for another
ready character, and if found don't return (context switch)
but instead go back to the start of the intr function and
process the character.  My driver did that, and on a PDP-11/34
we had a couple of dozen concurrent users of 9600bpi terminals
with great response.

I have a KMC11B sitting around, and some day I'll look into
whatever problems there might have been.  The idea of a front-
end processor was right, even if the implementation wasn't.

> how much time have i wasted with rs-232 junk?  too much.

However, it's as near to universal as one can get, even today.
I have a paper tape reader and an Apple IIGS attached to my
PCs via RS-232-C.  (The magtape is on SCSI.)