2. Qbus systems
by Ákos Varga (Hamster)

2.1  Introduction
2.2 LSI-11 and MicroPDP-11 systems
2.2.1  LSI-11 and LSI-11/2
2.2.2  LSI-11/23 and MicroPDP-11/23
2.2.3  Qbus systems based on the DCJ11 chip  LSI-11/73  PDP-11/53  PDP-11/83  PDP-11/93
2.3  MicroVAX and VAX systems
2.3.1  MicroVAX I, VAXstation I
2.3.2  MicroVAX II, VAXstation II, VAXstation II/GPX
2.3.3  MicroVAX III  MicroVAX 3500, MicroVAX 3600, VAXstation 3200  MicroVAX 3800, MicroVAX 3900  MicroVAX 3300, MicroVAX 3400
2.3.4  VAX 4000/200
2.3.5  VAX 4000/300
2.3.6  VAX 4000/400
2.3.7  VAX 4000/500

Full Table of Contents

Note: These pages are for informational purposes, I cannot be held responsible for damages, loss of information/hardware or injuries. Take precautions, we're talking about sensitive equipment and electricity here! I gathered the information from handbooks, catalogs, UseNet postings and from my own experience, so I might be wrong here and there. Please mail me, if you find something that doesn't seem right!

2 Qbus systems

2.1 Introduction

The Digital qbus was mostly used in the PDP-11 and VAX computer line, and products based on them, although there was one MIPS Rxxxx-based RISC computer, the DECsystem 5000/400, a.k.a. "MIPSfair". This means, that you can find it in systems using the following names: LSI-11, LSI-11/2, LSI-11/03, PDP-11/03, LSI-11/23, MicroPDP-11, MicroPDP-11/23, LSI-11/73, MicroPDP-11/53, MicroPDP-11/83, MicroPDP-11/93, MicroVAX I, VAXstation I, MicroVAX II, VAXstation II, VAXstation II/GPX, MicroVAX 3500, VAXserver 3500, VAXstation 3200, VAXstation 3500, MicroVAX 3600, VAXserver 3600, DECsystem 5400, MicroVAX 3300, VAXserver 3300, MicroVAX 3400, VAXserver 3400, MicroVAX 3800, VAXserver 3800, MicroVAX 3900, VAXstation 3900, VAX 4000/200, VAX 4000/300, VAX 4000/400, VAX 4000/500, DECserver 5000, DECserver 5400. These are all systems based on the qbus, so you have to know: the small label on the front of the enclosure doesn't says what's in there: LSI-11 systems can be upgraded to MicroPDP-11 systems, MicroPDP-11 systems can be upgraded to MicroVAX systems, DECserver 5000/5400 systems can be upgraded to MicroPDP-11 or MicroVAX systems, DECsystem 5400's can be converted to MicroVAX 3500's, etc. Also, a BA23/BA123 MicroVAX II system upgraded to a MicroVAX 3500 is sometimes called "MicroVAX III". A VAXserver is a MicroVAX with a license limit for only one interactive user, a VAXstation is a MicroVAX with graphics head. You'll have to open the box and see the CPU module to make sure what you have there.

You can also find qbus-based systems embedded in other systems: the qbus was originally aimed at the OEM industry. For example LSI-11-based systems are used in big Xerox graphics printers, Siemens telephone exchanges, etc... Most of the times these systems can be converted into standalone computing systems (with the removal of specific cards, replacing PROM's, EPROM's. (The DECserver 5000 is a nice example: it's a MicroPDP-11/53 system with special PROM's to make it act as a terminalserver). There were also third-party products which used the qbus as the main system interconnect (e.g. UNIVAX from ???).

Interesting pieces of history are the qbus systems manufactured in the "Easern Bloc" (COMECON countries, socialist/communist states) during the '80s). They're interesting, because the systems that have CPU's manufactured there are -although electronicaly compatible- different from the originals. The backplane and the cards were designed in metrical sizes: the cards cannot be used in "real" qbus backplanes (they're slightly bigger, and the different-sized edge-connectors would cause a short circuit). The soviet "Elektronika" company and the hungarian Central Research Institute for Physics built LSI-11/MicroPDP-11 compatible systems with this "metric qbus".

2.2 LSI-11 and MicroPDP-11 systems

Coming soon...

2.2.1 LSI-11 and LSI-11/2

2.2.2 LSI-11/23 and MicroPDP-11/23

2.2.3 Qbus systems based on the DCJ11 chip LSI-11/73 PDP-11/53 PDP-11/83 PDP-11/93

2.3 MicroVAX and VAX systems

Coming soon...

2.3.1 MicroVAX I, VAXstation I

2.3.2 MicroVAX II, VAXstation II, VAXstation II/GPX

2.3.3 MicroVAX III MicroVAX 3500, MicroVAX 3600, VAXstation 3200 MicroVAX 3800, MicroVAX 3900 MicroVAX 3300, MicroVAX 3400

2.3.4 VAX 4000/200

2.3.5 VAX 4000/300

2.3.6 VAX 4000/400

2.3.7 VAX 4000/500

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Copyrights: Ákos Varga, 1999 Last modified: