unix & real time -- is a rewritten UNIX still UNIX?

[Mike Gallaher]

	From: Bill Shannon <shannon at sun.uucp>

	[handling] 9600 baud asynchronous input with little or no hardware
	buffering.  On the Sun our approach to guaranteeing that we could
	service the interrupt as soon as possible was to make the UARTs
	interrupt at a priority higher than the system used for anything else,
	even the clock.

I've suspected for a while that that is the reason why the time of day
clock on our Sun 120 loses up to an hour or more a day, depending on
"system activity", which turns out to be "serial port usage".
We have two 9600 baud ports and a 1200 baud uucp port.  The
hardware clock is accurate, but the system time is set by it only at
boot time.

mike gallaher
....!sun!sunrise!unipress!mg
mg at rutgers
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