LSI-11

The LSI-11 was DEC's first cost-reduced PDP-11 processor, using the QBUS. Several different LSI-11 models exist, including the KDF11-F (quad form factor), and the KD11-HA (dual form factor), also called the LSI-11/2.

However, they all use the same chip set internally, the Western Digital WD16/CP1600 (alternative designations). The chip set consists of a data path chip, a control chip, and two or three microcode ROMs (each holding 512 words which are 22 bits wide). The uROMs all have the same pinout, and are wired in parallel, so they can be placed in any of the three uROM positions.

The first two uROMs contain the basic PDP-11 instruction set; the third uROM is optional, and a number of different choices are available. One is the KEV11-A, for the EIS/FIS instructions; the KEV11-B provides EIS without FIS. The KEV11-C provides a subset of the PDP-11 CIS, sometimes known as DIS (DIBOL instruction set).

LSI-11

The LSI-11 is a quad board (M7264) with additional functionality on-board (making possible a single-board computer): the base KD11-F version includes 4KW of MOS RAM; the KD11-H version has the RAM deleted; the KD11-Q includes the KEV11-C.

The chip order (from the left, with the contact finger edge down, and the component side facing the viewer) is KEV11, uROM 1, uROM 0, Control, Data Path.

LSI-11/2

The LSI-11 is a dual board (M7270); it contains the processor, and nothing else.

Note that the image in the "Microcomputer Products Handbook" (pg. C-18) is erroneous; the order of the chips (from the handle end) is, in fact, KEV11, Control, uROM 1, uROM 0, Data Path (per the KD11-HA print set); the order given in the Handbook is that for the LSI-11 (no doubt an image was re-used without checking).

Chip variants

There are a number of variants of all the various uROM chips; it is not known if all variants are completely interoperable (i.e. any revision of any chip can be replaced with any other, and have the machine still work), so combinations will be listed.

Chip numbers of the form 23-xxxxx-rr, etc are DEC part numbers (where 'rr' seems to represent a revision number - 0, if not given); the corresponding Western Digital numbers are xxxxy, etc (where the 'x's are digits, and the 'y' a letter). The Data Path chip is a 1611H (various DEC part numbers), and the Control chip is a 2007C (ditto); the uROM chips are all 30xxy.

The following sets (Data, Control, uROMs) have been observed (the first three on dual cards):

• 1611H 21-11549-01, 2007C 23-002C4, 3010A 23-001B5, 3007D 23-002B5
• 1611H 21-16890, 2007C 23-002C4, 3010D 23-001B5, 3007D 23-007B5
• 1611H 21-16890, 2007C 23-003C4, 3010D 23-008B5, 3007D 23-007B5
• unknown, unknown, 3010D 23-001B5, 3007D 23-002B5

The 3010D contains uROM addresses 0x000-0x1ff, and the 3007D 23-002B5 contains 0x200-0x3ff.

For the KEV11-A, one version is a 3015 23-003B5 (seen with the first set above), which is suitable for the M7270 quad card etch revisions E and F, and the M7264 dual card. Another version is reported to be the 23-091A5, suitable for the M7270 quad card, etch revisions C and D.

For the KEV11-B, one version is known, the 23-090A5; it is suitable for the M7270 quad module etch revisions C and D.

The KEV11-C uses two uROMs, the 23-004B5 and 23-005B5. (There may also be a hybrid - i.e. single DIP carrier - version of the KEV11-C, but the part number is unknown.)

Links

• Microcode disassembler