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To: Don Yuniskis <dgy@rtd.com>
cc: freebsd-hackers@freefall.FreeBSD.org (FreeBSD hackers)
Subject: Re: Watchdog timers (was: Re: Multi-Port Async Cards) 
In-reply-to: Your message of "Thu, 01 Feb 1996 00:57:18 MST."
             <199602010757.AAA19863@seagull.rtd.com> 
Date: Thu, 01 Feb 1996 00:26:32 -0800
Message-ID: <4664.823163192@time.cdrom.com>
From: "Jordan K. Hubbard" <jkh@time.cdrom.com>
Sender: owner-hackers@FreeBSD.ORG
Precedence: bulk

> Does this gizmo *need* to reside within the "PC"?  Are you really
> wanting to let it grab the bus, poke around, etc.?  Or, would something
> more "passive" suffice (i.e. sitting on a serial port external to the 
> PC)?

Actually, I kind of liked the idea of letting it grab ahold of the
bus.  It seems that a lot of problems one runs into in PCs these days
stem from individual cards or chipsets not *quite* playing by the
rules, and at times like that you really do want to watch every IRQ
line and have little service routines that are called when one changes
state, or whatever.  It's the only way to tell if someone's bogusly
generating an interrupt, or to generate one yourself if you're trying
to simulate some weird peripheral.

Not that I ever expected to *build* something as grandiose as I what
was talking about, I just like to fantasize about weird
peripherals. :-)

I think we're also probably dealing with several problem spaces here,
not one.  One set of people want a dumb robot, hacked out of discrete
logic if necessary, that does simple timing and watchdog tasks.
Another set of people want a full-blown system for dropping into a PC
and diagnosing its behavior right down to individual state transitions
on the bus.

I can see how both might be very useful things to have, in certain
situations.  I don't think that they necessarily have to be the same
card. :-)

I can also see where maybe you just want to design a dumb card that
enables one PC to take over another.  Then your PC on a card can just
be a PC on a PC. :-) All the intelligence would be in the device
driver.

					Jordan