Date   : Wed, 25 Aug 1982 00:13:01-EDT (Wed)
From   : Keith Petersen <w8sdz@BRL>
Subject: Re: MODEM221 Overrun Problems

Many MANY revisions back in "MODEM2xx" I changed the old original time-out
values to 10 seconds to allow for slow disk systems.  I have a Micropolis
Mod II mini-floppy that has a 30 millisecond track-to-track seek time and
it was constantly screwing up everytime it crossed a 16k extent boundry
because it had to seek back to the directory and then back to the data
area again, and by that time the sender was already sending the next
sector.  Somewhere along the line someone thought they "knew better"
and changed my 10 second values to much lower values.  I have seen
them as low as 3 and as high as 7.  My experience is that 10 was the
minimum reliable value for very slow disk systems and since the time-out
loop includes the input and it does not slow down the program to have it
set for 10 seconds, I see no reason to have it be less than that!

There are two timings involved in MODEM2xx.  1) the timing between
received bytes, which is set for one second maximum, and 2) the
timeout value between sectors, which as I said above should be 10
seconds.

There has been some discussion lately about some between-byte delays]
caused by heavy system load, which caused the 1-second byte timeout
to cause problems.  It would probably be a good idea to consider
changing that to 3 seconds, but I wouldn't increase it too much more
because it might cause problems getting back into "sync" after some
line disturbance or over-run.