These were PDP-8 compatible systems, designed when computing entered the deskside/desktop era. The PDP-8 was a quite successful architecture, you can read more about it here. The information on this page is not really extensive, as I don't have any first-hand experience and much knowledge about them. Please help me here!

WT78 (DECstation)
DECmate I
DECmate II
DECmate III

WT78

Picture 1: The Digital WT78

The WT78 was a small PDP-8-based system packaged into a VT52 CRT terminal; it was introduced around 1978, and was also known as DECstation or DECstation 78. The computer itself was housed on top on teacart-style "vehicle", which had an RX01 mounted beneath. The heart of the machine was the Intersil/Harris 6100 microprocessor, driven at 2.2 MHz. Standard amount of memory was 16 Kwords.

DECmate I

Introduced in 1980, the DECmate was the successor of the WT78. It was based on the Harris 6120 microprocessor running at 10 MHz, and was housed in a VT100 CRT terminal. It was a very limted model, no EAE option was available, memory was 32 Kwords. Similar to the WT78, it used a 8"  dual floppy drive, this time the RX02.

Options:
DP278-A and -B: Communication ports
RL278: 1 to 4 RL02 cartridge disk drives

DECmate II

Picture 2: DECmate II (system unit + VT201 keyboard + VR201 monochrome monitor)

A machine with a more open architecture than the previous DECmate. The official designation was PC27X, as the machine was one of the DEC "almost-PC" triumviate (which consisted of the PDP8-based DECmate II, the PDP11-based Professional and the dual (Z80/i8088-based) Rainbow) introduced in 1982. The processor was the Intersil 6120 microprocessor, standard memory was 32 Kwords, it had control panel function emulation. The enclosure incorporated an RX50 dual 5.25" floppy drive (with a special format, not the IBM-style 360 KB), and had space for a full-size 5.25" hard disk. Also on-board was a graphics adapter.

Options:
PC27X-A: APU (auxhillary processor unit), a Z80-based coprocessor with 64 KB memory (the DECmate could run CP/M using it)
PC27X-B: Hard disk controller
PC27X-?: XPU (extension processor unit), an i8086-based coprocessor with 256/512 KB memory (for MS-DOS)
RX78: adapter for using RX01/02 8" floppy drives

DECmate III

Picture 3: DECmate III (system unit with RX33 floppy + LK201 keyboard + VR201 monitor + expansion box with RX50)

Also know as PC23X, it was introduced in 1984, and was in fact an enhanced version of the DECmate II. Standard memory was 64 Kwords.

Options:
PC23X-A: Z80-based APU
PC23X-C: color graphics adapter
PC23X-D: integral modem

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