LSI-11 Processors

Overview

The LSI-11 processor is a microcomputer that was originally designed for OEM use, and meant to be integrated in third-party products. It was later packaged and sold by DEC as the PDP-11/03 line of production computers.

The processor has a 16-bit address bus and a 16-bit data bus. It can address up to 64 KB (32 KW) of memory and reserves the top 8 KB (4 KW) of the address space for I/O devices. This leaves up to 56 KB (28 KW) of memory for programs and data. Some configurations allow the I/O area to be reduce to 4 KB, allowing up to 60 KB (30 KW) of memory for programs.

In the table below, I broke out each processor by model number to illustrate the base variations. I many cases, the variation between two models was simply the addition of a chip, or chipset. For instance, adding an EIS/FIS chip to a KD11-F processor changes its model number to KD11-L.

LSI-11 Processors and Their Capabilities
Processor LSI-11 LSI-11/2
Module Number M7264 M7264-BB M7264-YA M7264-YB
M7264-YC
M7270
Model Number KD11-F KD11-L KD11-P KD11-H KD11-N KD11-Q KD11-H KD11-N KD11-HA KD11-NA
Introduced 1975 1975 1977 1976 1976 1977 1980 1980 1977 1977
Discontinued 1977 1977 1984 1980 1980 1982
Module Size Quad Quad Quad Quad Quad Quad Quad Quad Dual Dual
Chipset LSI-11 LSI-11 LSI-11 LSI-11 LSI-11 LSI-11 LSI-11 LSI-11 LSI-11 LSI-11
DIS Instructions optional1,3 no2 yes optional1,3 no2 yes optional1,3 yes optional1,2 no2
EIS Instructions optional5 yes yes optional5 yes yes optional5 yes optional4 yes
FIS Instructions optional6 yes no optional6 yes no optional6 no optional4 yes
Memory Management no no no no no no no no no no
Performance (VUP) 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05
Clock Period (ns)7 360-4008 360-4008 360-4008 360-4008 360-4008 360-4008 360-4008 360-4008 380 380
Q-bus Address Size 16-bits 16-bits 16-bits 16-bits 16-bits 16-bits 16-bits 16-bits 16-bits 16-bits
Q-bus Interrupts 1-level 1-level 1-level 1-level 1-level 1-level 1-level 1-level 1-level 1-level
RAM Capacity 64 KB 64 KB 64 KB 64 KB 64 KB 64 KB 64 KB 64 KB 64 KB 64 KB
Onboard RAM 8 KB 8 KB 8 KB no no no no no no no
Onboard ROM no no no no no no no no no no
ODT Microcode yes yes yes yes yes yes yes yes yes yes
Memory Refresh yes yes no9,10 yes yes no9 yes yes no no
Termination (ohms) 250 250 250 250 250 250 250 250 220 220
AC Bus Load 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 1.7 1.7
DC Bus Load 1 1 1 1 1 1 1 1 1 1
+5V Load 1.8 A 1.8 A 1.8 A 1.8 A 1.8 A 1.8 A 1.8 A 1.8 A 1.2 A 1.2 A
+12V Load 0.8 A 0.8 A 0.8 A 0.8 A 0.8 A 0.8 A 0.8 A 0.8 A 0.22 A 0.22 A

1 Requires the KEV11-CA 23-004B5 & 23-005B5 DIBOL chip set.
2 The DIS and EIS/FIS chipsets are mutually exclusive.
3 Requires etch Rev E or F.
4 Requires the KEV11-A (23-003B5) EIS/FIS processor chip.
5 Etch Rev C requires the KEV11 23-091A5-01 EIS/FIS processor chip.
  
Etch Rev D requires the KEV11 23-091A5-01 EIS/FIS processor chip, or the KEV11-B 12-090A5-01 EIS-only processor chip.
  
Etch Revs E & F require the KEV11-A 23-003B5 EIS/FIS processor chip.
6 Etch Revs C & D require the KEV11 23-091A5-01 EIS/FIS processor chip.
   Etch Revs E & F require the KEV11-A 23-003B5 EIS/FIS processor chip.

7 Clock frequency = 1 / Clock Period (e.g. 1 / 400 ns = 1 / 0.0000004 = 2,500,000 Hz, or 2.5 MHz)
8 Module has a variable frequency oscillator, so the period may vary slightly.
9 The DIBOL chipset does not have microcode refresh.
10 A system must be equipped with an REV11 module to perform the onboard memory refresh operation.

Due to the number of variations in M7264 module numbers, referenced in the DEC documentation, I went ahead and broke out the differences between them. Most have to do with the RAM chip manufacturer used.

M7264 variations
Variation Description
M7264 Processor with 350ns Mostek 4096 RAM
M7264-AA M7264 or M7264-AB, CB, DB, EB, FB, HB, JB
M7264-AB Processor with 350ns Intel 2104 RAM
M7264-BB Processor with 350ns Mostek 4096 RAM and DIBOL microm
M7264-CB Processor with 350ns Fujitsu 8224 RAM
M7264-DB Processor with 350ns Intel 2104A RAM
M7264-EB Processor with 200ns Mostek 2047 RAM
M7264-FB Processor with 200ns DEC 2047 RAM
M7264-HB Processor with 200ns Motorola 2047 RAM
M7264-JB Processor with 200ns Fujitsu 8227 RAM
M7264-YA Processor with no onboard RAM
M7264-YB Processor with no onboard RAM and DIBOL microm
M7264-YC Processor with no onboard RAM (replaced the M7264-YA)

I also broke down the more common KD11 variations, to clarify their differences.

Q-bus KD11 Variations
Variation Description
KD11-F LSI-11 processor, 4KW MOS RAM onboard
KD11-H LSI-11 processor, no onboard RAM
KD11-J KD11-H packaged with a MMV11-A 4KW core memory module
KD11-L KD11-F with EIS/FIS
KD11-M KD11-J with EIS/FIS
KD11-N KD11-H with EIS/FIS
KD11-P LSI-11 processor with DIBOL microm, 4KW MOS RAM onboard
KD11-Q LSI-11 processor with DIBOL microm, no onboard RAM
KD11-R KD11-H packaged with a MSV11-CD 16KW MOS memory module
KD11-S KD11-R with EIS/FIS
KD11-U KD11-H packaged with an MRV11-BA EPROM module
KD11-HA LSI-11/2 processor
KD11-NA LSI-11/2 processor with EIS/FIS

Summary

Probably the more desirable processor to own is the M7270 LSI-11/2. It has all of the relevant capabilities that the larger M7264 has, but takes up less space in the card cage. It is fairly common and affordable.

An early KD11-F, or KD11-J, with a core memory board would also be desirable, for historical preservation purposes. An M7264 with the DIBOL (commercial) instruction set would be collectable, due to its rarity.

References

Additional Resources


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