Subject: Re: DECsystem 5500 (was Re: system 5900)
To: Warner Losh <firstname.lastname@example.org>
From: Dave McGuire <email@example.com>
Date: 08/13/1999 15:30:31
On Fri, 13 Aug 1999, Warner Losh wrote:
>No. I don't think that it did. i do know that the MicroVAX II I
>managed back in the late 1980s had several doublewide cards, but the
>terminal card was single wide. Nothing worked until DEC Field Circus
>came out with a bus grant card (I believe that was the name) to fill
>in the other half of the double wide slot. Then everything started
>working again. I guess it was good the school had two DECsystem 20's
>so it rated its own Field Service person who came out on site often
>enough he just dropped the card by one day and kept it off the books
>(since we were part of the school, but a different part, the
>accounting for these things got funny).
Grant cards are required to maintain continuity of the bus grant lines...they
are wired to each slot and must go *through* each board to reach all boards on
the bus. If a given board doesn't use those lines, it simply jumpers them
together. A bus grant card does just that.
Unibus does things in a similar way, but the grant cards are very
small...about 2"x2"...and sit way down into the backplane in such a way that
virtually guarantees bloody knuckles if you work on them enough.