Restoration of a PDP-8a - test-drb@ccmp.vtda.org

15 Jan 2014

...
  Message: 21
 Date: Wed, 15 Jan 2014 06:37:59 -0500
 From: Bob Vines <bobvines00 at gmail.com>
 To: cctech at classiccmp.org
 Subject: Re: Restoration of a PDP-8a
 Message-ID:
 	<CAPDUT-=Vd2iYTC=u97rjnr5O=Hk1wv+Ltpf9uKphABWNzdOi7g at mail.gmail.com>
 Content-Type: text/plain; charset=ISO-8859-1

 ------------------------------

 Message: 12
 Date: Tue, 14 Jan 2014 10:24:57 +0000
 From: anders at abc80.net
 To: "General Discussion\: On-Topic Posts Only" <cctech at
classiccmp.org>
 Subject: Re: Restoration of a PDP-8a
 Message-ID:
         <20140114102457.Horde.jcUVy0nXMOJSjET97Z2yBA7 at blue.abc80.net>
 Content-Type: text/plain; charset=UTF-8; format=flowed; DelSp=Yes

 Hi,

 Slowly my restoration project continues. I have repaired the power
 supply and I actually found and bought a programmers console. I also
 got a DKC8-A in etch revision D. I have now all the boards needed for
 getting this machine running.

 Is the two cables between KC8 and DKC8 just two strait 40 pin cables?

 I have a question about memory configuration. I have two core stacks
 from different suppliers. One from DEC and one from Dataram corp. The
 later one is impossible to find any information on. The DEC stack is a
 MM8-AB 16k module but the address field configuration looks strange.
 If I interpreted the manual correct it's configured as a 8k module
 using field 4-5.

 Picture of the jumpers on the actual board:
 http://www.abc80.net/docs/pdp8/pdp8a/DSC_2258.JPG

 Pictures on the complete board on both sides.
 http://www.abc80.net/docs/pdp8/pdp8a/DSC_2252.JPG
 http://www.abc80.net/docs/pdp8/pdp8a/DSC_2253.JPG

 The board is known good and does not origin from this particular machine.

 Does anybody know why this looks like this?

 /Anders

 The PDP-8/A Operator's handbook at

http://bitsavers.informatik.uni-stuttgart.de/pdf/dec/pdp8/pdp8a/EK-8A001-OP…,
 page 3-30 states that two BC08R cables are used.  The Digital Cables
 Handbook at http://www.pdp8online.com/bklatt/cables.html describe the
 BC08R on pages 30 & 31.  Page 31 shows the pinout. 
Great, I have missed that one.

...

 About the Dataram module:  Does any of the info at
 http://bitsavers.informatik.uni-stuttgart.de/pdf/dataram/ help?  Also,
 there is a Dataram company (http://www.dataram.com/) still in business
 providing computer memory products (since 1967).  Have you tried to
 contact them?  You might get lucky, especially if they like the idea
 of one of their "early" products still in operation after 30+ years.

I'll try to contact them. I have already tried bitsavers.org

...
  The MM8-AA & MM8-AB Engineering Specification at
 http://www.pdp8online.com/pdp8cgi/query_docs/tifftopdf.pl/pdp8prints/mm8aa.…
 shows that your jumpers are in locations 1-3 & 3-4.  It then states
 that those two jumpers, in combination, will configure the module for
 memory locations 32K-48K, which it then states are "presently not
 available."  But it was written in 1975.  However, the 1978 KT8-A
 Memory Management Control (EK-KT08A-UG-001 at
 http://bitsavers.informatik.uni-stuttgart.de/pdf/dec/pdp8/pdp8a/EK-KT08A-UG…)
 allows an -8/A to use up to 128K of any -8/A memory type.  Perhaps the
 previous user of the MM8-AB module had the KT8-A module to allow the
 use of more than 32K? 
Ok. Thanks. That explains it I think.

/Anders