Path: utzoo!attcan!uunet!samsung!brutus.cs.uiuc.edu!lll-winken!ames!ncar!unmvax!pprg.unm.edu!swilson
From: swilson@pprg.unm.edu (Scott Wilson [CHTM])
Newsgroups: comp.sys.dec.micro
Subject: Re: Unix for 11/23 (18-bit)
Message-ID: <26911@pprg.unm.edu>
Date: 22 Mar 90 15:48:10 GMT
References: <694.26076f6d@ubvms.cc.buffalo.edu>
Reply-To: swilson@pprg.unm.edu (Scott Wilson [CHTM])
Distribution: na
Organization: U. of New Mexico, Albuquerque
Lines: 36

In article <694.26076f6d@ubvms.cc.buffalo.edu> v076n3w7@ubvms.cc.buffalo.edu writes:
>The memory limitations, however, are in the backplane.
>
>If the backplane being used is a BA11-SA, then it's 22-bit. 
>
>I forgot the other types of q-bus backplanes, but I think the 
>BA11-N is 18- or 16-bit.
>
>Chris Kalisiak
>V076N3W7@ubvms.bitnet
>v076N3W7@cc.buffalo.edu


This is indeed the case. However, if you are brave, you can whip out your
handy wire-wrap tool and add the missing lines to your backplane! I have
done this several times. Just be sure to follow the LSI-11 Bus Technical
Specs.

This sometimes doesn't work (on real old backplanes) because DEC connected
all the SPAREx lines that would later become BDAL{18-21} to the ground plane!
On some other backplanes these were bussed between slots, but just werent
used. On others they are not bussed, but not connected between slots either
and these are the ones you can wire-wrap to be full Q22. Just be sure
to keep the wires close the backplane or you may mess up the RF impedance
of the added lines.

Check out your backplane with VOM (and with all the cards out) before you
start to be sure you get everything right.

Scott Wilson
University of New Mexico
Center for High Technology Materials
Albuqerque, NM 87131
(505)277-0780

swilson@bullwinkle.unm.edu