19 Jun
2005
19 Jun
'05
9:01 p.m.
Subject: Re: PDP11/23+ goes on
From: Al Kossow <aek at bitsavers.org>
Date: Sun, 19 Jun 2005 18:51:57 -0700
To: classiccmp at classiccmp.org
The RQDxx controllers are a bit clunky to use with their
breakout panel if you aren't putting it into a box designed
for it.
Use the brakout designed for the BA123 to breakout a RQDX.
Just put the breakout card in some unused but powered slot
(last ore beyone the last) and it will be powered and
expand to multiple drives. I have my 11/73 with the 18/AB
backplane that way.
I still say that the simplest thing to do is just to
find
a used Qbus MSCP SCSI conroller though.. If you can find
someone scrapping Qbus microvaxen, they often have them
hiding inside (that's where I got the ones that I have).
It is.
The problem with QBUS PDP-11 IDE is that I've not seen a
design that has a DMA implementation which make it slow.
Also drivers for common PDP-11 OSs other than unix are
roll your own, wich is possible IF you already have a
working system (with editors and asm).
What makes the Qbus interface for IDE nasty is the
PDP-11 read before write. That means you have to make
the read addresses seperate from the write addresses.
However, in the last few years there is the possibility
of a flash ram disk as devices in the multimegabyte range
are available. Qbus non rotating media, hummm. There
one for the builders to consider.
Allison