The /40 was introduced in January, 1973. It was a higher performance version of the /20, with a microcoded two-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.