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From: terry@spcvxb.spc.edu (Terry Kennedy, Operations Mgr.)
Newsgroups: comp.sys.dec
Subject: Re: "passive release"?  What is it?
Message-ID: <1991Feb12.044547.1097@spcvxb.spc.edu>
Date: 12 Feb 91 04:45:47 GMT
References: <GOEHRING.91Feb11202106@ai.mit.edu>
Organization: St. Peter's College, US
Lines: 22

In article <GOEHRING.91Feb11202106@ai.mit.edu>, goehring@ai.mit.edu (Not Marc Spencer) writes:
> The _VAX Architecture Reference Manual_ specifies that SCB vector 00
> is for a "passive release" interrupt.  What is a "passive release",
> what causes one, what is the OS expected to do with one of these, and
> what parameters are pushed on the stack?

  In brief, when a device asks for the bus via interrupt request, but
then decides to ignore the interrupt ack from the Unibus adapter. Thus,
the ack progresses through the backplane. If no other device grabs it,
it hits the terminator.

  Thus, no vector is passed to the processor, and you get the default
vector.

  From an application point of view, you'll never see this. From the
driver's point of view, it won't either (but it should avoid placing the
hardware in a state where it will generate passive releases, as they
delay bus operations.

	Terry Kennedy		Operations Manager, Academic Computing
	terry@spcvxa.bitnet	St. Peter's College, US
	terry@spcvxa.spc.edu	(201) 915-9381