From: jnc@mercury.lcs.mit.edu (Noel Chiappa)
Subject: [TUHS] DH11 flaw Was: pre-more pager?
Date: Wed, 8 Nov 2017 16:27:53 -0500 (EST) [thread overview]
Message-ID: <20171108212753.C800818C0B9@mercury.lcs.mit.edu> (raw)
From: Ron Natalie
> We actually still had some real DEC DH's on our system.
> ...
> At least the DZ doesn't loop on the ready bit like the kernel printf
This reminds me of something I recall reading about John McNamara (designer of
the DH11) admitting that he'd screwed up a bit in the DH design; IIRC it was
that if you set the input silo alarm (interrupt) level to something greater
than 1 character, and someone types one character, and then nothing
else... you never get an input interrupt!
(Which is why some Unix DH driver which sets the silo alarm level > 1 - to get
more efficient processing by reducing the number of interrupts _if possible_ -
has to call a 'input characters ready from the DH' routine in the clock
interrupt code.)
IIRC McNamara said he should have included a timeout, so that if the silo
count was non-zero,and stayed that way for a while, it should have caused
a timeout, and an interrupt.
I was just looking for this, but couldn't find it. I thought it was here:
http://woffordwitch.com/McNamaraDH11.asp
but it doesn't seem to be. Does anyone recall seeing this anywhere, and if so,
where? Web search engines didn't turn anything up, alas...
Noel
next reply other threads:[~2017-11-08 21:27 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-08 21:27 Noel Chiappa [this message]
2017-11-08 21:49 ` Clem Cole
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