|Year Introduced:||June 1972|
|Word Size:||16 bit|
|Physical Address Size:||18 bit|
|Virtual Address Size:||16 bit|
The difference between the two CPUs was whether they worked with the FP11-B or FP11-C FPP. The FP11 Floating-Point Processor was optional, as was the KT11-C Memory Management Unit (the first implementation of the full PDP-11 Memory Management).
The PDP-11/50 and PDP-11/55 were systems which used the exact same processor, but were sold pre-configured with the special high-speed MS11 Semiconductor Memory System (specific to the PDP-11/45), using 350 nsec MOS or 300 nsec bipolar memory, respectively.
The high-speed memory could be configured in two semi-independent banks, each with its own M8110 (later M8120) Semiconductor Memory Control module.
Quoting: Introduced two years after the PDP-11/20, in June 1972. The KB11 was a faster, microcoded CPU built with SSI/MSI (Small/Medium Scale Integration) components. The machine had two different buses: one was a UNIBUS with 18-bit addressing, the other was a fast CPU-memory interconnect. It also introduced split I/D (Instruction/Data) spaces (UNIX used this; the DEC operating systems did not), an MMU (Memory Management Unit) option, an optional FPU (Floating Point Unit). The maximal ammount of memory was 128 Kwords.
The cycle time of the PDP-11/45 with bipolar memory (max. 8 KW!) was 300 ns, MOS memories (max. 32 KW) were 450 ns, and core was 980 ns - but without memory management! The MMU added 90 ns to the cycle time.
The PDP-11/50 was basically the same machine with different memory. The PDP-11/55 (KB11-D CPU) used the modified CPU of the PDP-11/70, where the cache was left out (instead the memory was the faster bipolar memory). It also had the kernel/supervisor/user operating modes seen on the PDP-11/70, but only had a 18-bit addressing range. It was the fastest of the "classic" PDP-11 CPU's when measured by the cycle times.
|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-11/34 • PDP-11/04 • PDP-11/44 • PDP-11/60 • PDP-11/24 • PDP-11/84 • PDP-11/94
Clones: CM 1420