µPDP11/53   PROCESSOR OVERVIEW M7554
INTRODUCTION
The µPDP11/53 processor modules exists in 13 variations. They have in common that they all have the QBUS architecture. The differences are (among others) the J11 processor clocked at 15 MHz or 18 MHz, the amount of RAM installed on the module (either 512 kbyte or 1.5Mbyte), and the physical construction ("normal" or with S-box handles). Here is a short table, taken from the Field Guide, maintained by Megan Gentry.

module number  module name    Description
  M7554  KDJ11-DA  J11 CPU 15 MHz, 512 kbyte RAM, 2 SLUs, LTC
  M7554-01  KDJ11-DA  J11 CPU 15 MHz, 512 kbyte RAM, 2 SLUs, LTC (VE)
  M7554-02  KDJ11-DB  11/53-PLUS CPU 15 MHz, 1.5 Mbyte RAM, 2 SLU, LTC
  M7554-04  KDJ11-DD  J11 CPU 18 MHz, 1.5 Mbyte RAM, 2 SLUs (CSS)
  M7554-PA  KDJ11-SA  J11 CPU 15 MHz, 512 kbyte RAM, 2 SLUs, with S-box handle
  M7554-PB  KDJ11-SB  J11 CPU 18 MHz, 512 kbyte RAM, 2 SLUs, LAT PROM, with S-box handle
  M7554-PC  CMR53-AA  J11 CPU 18 MHz, 512 kbyte RAM, 2 SLUs, with S-box handle, CMR53 boot PROM
  M7554-SA  KDJ11-SA  J11 CPU 15 MHz, 512 kbyte RAM, 2 SLUs, with S-box handle (VE)
  M7554-SC  KDJ11-SC  J11 CPU 15 MHz, 512 kbyte RAM, 2 SLUs, with S-box handle (VE)
  M7554-SD  KDJ11-SD  J11 CPU 18 MHz, 1.5 Mbyte RAM, LAT ROM, with S-box handle
  M7554-SE  KDJ11-SE  J11 CPU 18 MHz, 1.5 Mbyte RAM, 2 SLUs, LTC, with S-box handle
  M7554-YA  KDJ11-SA  J11 CPU 15 MHz, 512 kbyte RAM, 2 SLUs, LTC, no handle
  M7554-YB  KDJ11-SB  J11 CPU 15 MHz, 512 kbyte RAM, 2 SLUs, LAT PROMs, no handle

KDJ11-DB MODULE
KDJ11-DB PDP11/53 PLUS M7554-02
The bulkhead panel of the µPDP11/53 has the following parts.
  • MMJ (Modified Modular Jack) connections for 2 serial lines
  • Baudrate setting rotary dials for the 2 serial lines
  • Rotary dial to select the boot device number
  • 7-segment display for the system status
 
The 11/53 processor module does not have any diagnose LEDs on the board like some other QBUS processor boards. The 11/53 processor module connects with a ribbon cable to the bulkhead panel at the rear side.
The bulkhead panel is specific for the processor module, that is, the bulkhead panel for the µPDP11/73 is different, and the bulkhead panels for the µPDP11/23, µPDP11/83 and /93 are all different.

KDJ11-DB bulkhead panel

J11 PROCESSOR CHIP
J11 processor chip

The "microPDP-11's" are all built with the J11 processor chip.
All previous PDP-11 processors are physically one or more boards.
For example the PDP-11/04 is a single hex module, the PDP-11/40 is four hex-height and one quad-height module, and the PDP-11/70 processor is more than 10 hex-height modules and a quad-height module. And that is only the basic system, no floating point or other options. The J11 is basically a complete PDP-11 processor of several big boards on a chip carrier!

The following µPDP-11 models were built: /23, /53, /73, /83, and /93.
The µPDP11/93 was the fastest of them all. These models all have one thing in common, their bus architecture, which is called "QBUS".
The /23, /83, and /93 are also built with the UNIBUS architecture, then they are called PDP-11/24, /84, and /94 (so without the "micro" prefix). There was never an 11/54. But there was a prototype called PDP-11/74, but that was quite something different! The PDP-11/74 is a system of four PDP-11/70 processors, making it a multi-processor system. Rumour has it that the PDP-11/74 was cancelled, as that machine was a threat to the new announced VAX machines. The PDP-11/74 outperformed the VAX!