PDP11/23+ goes on

[Allison]

>
>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