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PDP-11/40 with TU56 dual DECtape drive.
Manufacturer: Digital Equipment Corporation
Word Size: 16 bit
Physical Address Size: 18 bit
Virtual Address Size: 16 bit
Bus Architecture: UNIBUS
A PDP-11/40 setup.

The PDP-11/40, introduced in 1973, using the KD11-A CPU, was the second machine to support 18-bit memory addressing on the PDP-11 platform, after the PDP-11/45.

The OEM version of the -11/40 is the PDP-11/35; the machines are completely identical, except for the printing on the front panel.

A special -11/40 with a blue front panel was used as the front-end for the KL-10 in DECSystem-10s and DECSystem-20s - though the 11/40 panel was hidden behind a cabinet door on the -20.

The 11/40 was also a primary platform for early UNIX.




The /40 was introduced in January, 1973. It was a higher performance version of the /20, with a microcoded multi-board CPU. 18-bit MMU (-> max. 128 kw memory), FPU and EIS/FIS (extended/floating point instruction set) were available options.

There was a 'graphical' workstation model of the /40, marketed as the GT44. Many /40s were used in DECsystem-10's (KL10's, to be exact), as the frontend/IO-processor. These were painted differently, the panel looks awsome in blue too. (no, it's not just the frontpanel, that I like about the -11...)

On the picture to the left we can see two RK05's (disk pack drives) and two TU60 (DECcasette) units. On this picture we can see a close-up at the frontpanel (with bootdevice-selector panel) and the paper-tape puncher/reader.

OS's at this point: DOS/BATCH, RSX11, RT-11, RSTS.

Trivia: The 11/40 was one of the most often "cloned" machine. the soviet/tscech/polish SM-4 (CM-4), the hungarian TPA-1140 are all copies of this computer.