The LSI-11 CPUs were DEC's first cost-reduced PDP-11 CPUs, using a microprocessor (the LSI-11 chip set). They also used a new bus, the QBUS.
They were the first PDP-11 models to not have a front panel to control them; instead, as a cost-reduction measure, the main serial line is used as a operating console, using the ODT functionality.
The first LSI-11 was a quad board (M7264) with additional functionality on-board. A later board, the LSI-11/2, packaged just the CPU on a dual card.
Note that ODT will not function correctly in the LSI-11s unless there is main memory on the QBUS. The reason for this restriction is unknown: the KDF11 CPUs and KDJ11 CPUs, which also use ODT, do not have this limitation; e.g. a system consisting only of a KDF11-A CPU and a serial console will run ODT.
Both LSI-11s are Q16 devices; they only drive 16 address lines. Although they can be plugged into a Q18 or Q22 backplane, they will only function with Q16 main memory. (With Q22 memory, the pins used for BDAL18-21 are used for other, internal signals by the LSI-11. The reason for the incompatability with Q18 memory is currently unknown.)
There were CPU options were available for the LSI-11s: 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 (it also apparently includes the EIS, but not the FIS).
They also supported the optional KUV11 Writeable Control Store.
|v • d • e PDP-11 Computers and Peripherals|
| UNIBUS PDP-11s - PDP-11/20 • PDP-11/15 • PDP-11/35 • PDP-11/40 • PDP-11/45 • PDP-11/50 • PDP-11/55 • PDP-11/70|
PDP-11/05 • PDP-11/10 • PDP-11/04 • PDP-11/34 • PDP-11/60 • PDP-11/44 • PDP-11/24 • PDP-11/84 • PDP-11/94
QBUS PDP-11s - PDP-11/03 • PDP-11/23 • PDP-11/23+ • MicroPDP-11/73 • MicroPDP-11/53 • MicroPDP-11/83 • MicroPDP-11/93
PDT-11s - PDT-11/110 • PDT-11/130 • PDT-11/150 CTI PDP-11s - PRO-325 • PRO-350 • PRO-380
Chips: LSI-11 • F-11 • T-11 • J-11 Clones: CM 1420
Also: PDP-11 architecture • PDP-11 Memory Management • PDP-11 stacks • FP11 floating point • UNIBUS • QBUS