DX20 Programmed Device Adapter
The DX20 Programmed Device Adapter was an adapter which could interface between an IBM-style channel bus and a MASSBUS. It can act as either a channel controller or a control unit on the channel bus. When operated as a control unit, in theory it could have been used to attach a DEC machine to a IBM System/370 (appearing as a device to the /370); it was mainly intended to allow use of OEM-produced peripherals on DEC machines.
It was principally intended for use on a KL10 system; it plugged into a RH20 MASSBUS controller on the KL10. (The original intended configuration was with a TX02 Magnetic Tape Controller, along with one or more TU70, TU71 OR TU72 magnetic tape drives; the ensemble was designated a 'TU70 Magnetic Tape Subsystem', or TU71 or TU72 as appropriate.)
Implementation
The DX20 is built around a microprocessor (in the old sense of the word; i.e. a block of logic which executes microcode. The microcode (2K of 16-bit μwords) is held in a 'writeable control store', and was loaded into the DX20 by the host processor after power-on.
The DX20 was composed of four major sub-systems - "microcontroller, [MASSBUS] computer interface, high speed data path, and a device [channel] interface" - held mostly on five hex boards (with a sixth optional), and two quad boards:
- M8602 microprocessor
- M8601? (control store memory)
- M8603 MASSBUS data (quad)
- M8604 MASSBUS control
- 3xM5903 MASSBUS transceiver (dual width)
- M6505 data storage (quad)
- M6506 data formatter
- M8607 channel bus
- M8608 channel extension (optional, for bus 1; only bus 0 is standard)
- G891 power fail and select (single width)
They plugged into a custom system unit-sized backplane, mounted in a separate cabinet (either an H950 or an H9502) along with the power supply. The manual states that the boards were wire-wrapped, which if accurate, indicates that the DX20 was produced in small numbers.
See also
External links
- DX20 Programmed Device Adapter Technical Manual (EK-0DX20-TM-PRE)
