DEC LSI-11 11/03 systems

This page Last updated Nov 2 2016. (c) Copyright Herb Johnson 2016

DEC's LSI-11 was their earliest product with a CPU on a set of large LSI IC's. Based on the PDP-11 instruction set, the LSI-11 used a non-UniBus backplane architecture called "QBus". An early CPU board was a quad-width KD11-F, and the DEC model was 11/03. These were first distributed in 1975. (I'm a little fuzzy about whether the LSI-11 and the 11/03 were the same or seperate.)

The CPU chip set was produced by Western Digital initially, and later sourced by DEC itself. The chip set was reused in other products of the era. DEC went on to produce other PDP-11's with various enhancements to this and subsequent CPU chip sets.

This Web page shows a DEC 11/03 CPU and H9270 frame / backplane, with Heath brand cards. I acquired it at the Trenton Computer Fest of April 2011. Some photos were added in Oct 2016.

To see other DEC systems and parts I have, visit my DEC reference page.

To email me or to order, see see my ordering Web page for my email addresses.

11/03 as acquired

[LSI-11 on frame]

Here's photos of the 11/03 and Heath cards I acquired at the 2011 TCF. The fellow took my email address and said he may have some documents at home to offer me. A look at the lable on the backplane, says this is the 11/03 with model H9270 backplane (H9270 is also on the box).This frame / backplane is dated Jan 1976.

The CPU board (KD11-F, M7264) is dated Oct 1975. I was told this was a $1000 item at the time. The four LSI chips (mid-1975) are: two ROMS (23087A501, 23088A501), a control chip 23001C201 and a data chip 21-11549. The fifth socket can hold an extended instruction set (EIS) chip (some variation of 23-003B5-00 or 23-009B5-00, WD number AC1631-???. Looking at some manuals for the M7264, there seems to be some variations in layout.

I also obtained a DEC M7940 console (serial port) card.

2011 dealer prices for the 11/03 CPU or backplane are between $100-$200. Dealer prices for the H9270 and subsequent backplanes are a few hundred dollars. Here's a 2016 photo of the H9270 I have, it's not marked -A or -Q, just "H9270".

The Heath company also offered an LSI-11 (possibly only the dual width CPU version?), and provided cards of their own. My purchase included two Heath static RAM cards, one bare, one with some sockets, as shown.

H9270 box from DEC with LSI-11
H9270 rack, from CPU side
H9270 rack, showing wirewrap base
H9270 rack, DC power connections
H9270 rack, card edge side
H9270 rack, wirewrap back
H9270 rack in box
label on H9270 rack
CPU area of processor card
4K X 16 RAM area of processor card
DEC serial card M7940
DEC serial card
Heath 85-2032-2 RAM card
Heath RAM card from back

Other Web sites describe the LSI-11 or 11/03, some in more detail than others. A Web search will be pretty productive. "Diane's PDP-11 Page" describes the various LSI chip sets. Various archives of "bitsavers" or "" have PDP-11 and 11/03 manuals. There's also archives on has many Web page links, some dead. There's a nice set of bootstrap options on Will's PDP-11 pages.

Herb Johnson
New Jersey, USA
follow this link to email @ me

Copyright © 2016 Herb Johnson