---
title: Mostek MD
categories:
- Computers
types:
- Professional Computer
origins:
- U.S.A.
years:
- '1979'
cpus:
- Z80
params:
  name: MD
  image: /media/museum/photos/mostek_md_system_1.jpg
  company: /companies/mostek
  company_name: Mostek
  specs:
  - label: NAME
    value: MD
  - label: MANUFACTURER
    value: Mostek
  - label: TYPE
    value: Professional Computer
  - label: ORIGIN
    value: U.S.A.
  - label: YEAR
    value: '1979'
  - label: BUILT IN LANGUAGE
    value: Monitor in ROM
  - label: KEYBOARD
    value: Depending of the video terminal used
  - label: CPU
    value: Z80
  - label: SPEED
    value: 4 Mhz
  - label: CO-PROCESSOR
    value: None
  - label: RAM
    value: 8 KB expandable to 64 KB
  - label: TEXT MODES
    value: 80 chars x 25 lines
  - label: SOUND
    value: No sound
  - label: SIZE / WEIGHT
    value: 54 (W) x 60 (H) x 44 (D) cm. / Heavy!
  - label: I/O PORTS
    value: 2 x serial, 2 x A/D-D/A, 1 x Parallel, video terminal
  - label: BUILT IN MEDIA
    value: 2 x 8
  - label: OS
    value: CP/M
  - label: POWER SUPPLY
    value: 3 x built-in power supply units (+24V for FDD / + 5V / +12 -12V)
  - label: PERIPHERALS
    value: All STD Bus cards
  - label: PRICE
    value: Unknown
  tabs:
  - photos
  - hardware
  photos:
  - title: COMPLETE SYSTEM
    subtitle: ''
    text: MD system with a Volker-Craig video terminal
    image: /media/museum/photos/mostek_md_withterminal_1.jpg
  - title: TERMINAL CLOSE-UP
    subtitle: ''
    text: ''
    image: /media/museum/photos/mostek_md_volkerterminal_1.jpg
  - title: 'BOTTOM RACK #1'
    subtitle: ''
    text: The bottom rack holds two 8" floppy drives
    image: /media/museum/photos/mostek_md_frontside_1.jpg
  - title: 'BOTTOM RACK #2'
    subtitle: ''
    text: The two impressive floppy drives with their own 24V power supply unit.
    image: /media/museum/photos/mostek_md_bottomrack_1.jpg
  - title: 'TOP RACK #1'
    subtitle: ''
    text: |-
      From left to right:

      \- CPU board\
      \- 32 KB RAM and Parallel port board\
      \- Dual serial port board\
      \- Floppy drives controller board
    image: /media/museum/photos/mostek_md_toprack_1.jpg
  - title: 'TOP RACK #2'
    subtitle: ''
    text: ''
    image: /media/museum/photos/mostek_md_toprack_2.jpg
  - title: 'BACK SIDE #1'
    subtitle: ''
    text: |-
      **(1)** +12V / -12V power supply unit\
      **(2)** +5V second power supply unit\
      **(3)** Dual 64 lines bus. Bottom bus is used for addresses and data lines, top bus is used for I/O. Main boards use the dual bus, some others **(5)** only use the bottom one.\
      **(4)** I/O cables. They are normally fixed to the back panel.
    image: /media/museum/photos/mostek_md_backopen_1.jpg
  - title: 'BACK SIDE #2'
    subtitle: ''
    text: |-
      **(1)** Z80 bus I/O connector\
      **(2)** Analogue / digital converter connector\
      **(3)** Composite video connectors. Video signal comes from the main CPU board.\
      **(4)** Parallel connector\
      **(5)** 2 x Serial connectors\
      **(6)** Video terminal connector
    image: /media/museum/photos/mostek_md_backclosed_1.jpg
  - title: WIRED BUSES
    subtitle: ''
    text: Notice that the system didn't use backplane but handy wired buses.
    image: /media/museum/photos/mostek_md_wiredbus_1.jpg
  - title: CPU BOARD
    subtitle: ''
    text: |-
      This board holds all the necessary chips allowing it to be used as a stand alone unit.

      **(1)** Mostek Z80 processor\
      **(2)** Step by step switch\
      **(3)** Reset switch\
      **(4)** 16 KB RAM memory (8 x 4116 chips)\
      **(5)** 4 KB Monitor ROMs (4 x 2708)\
      **(6)** Z80 CTC - Counter Timer Circuit\
      **(7)** 2 x Z80 PIO - Parallel Input Output Controllers
    image: /media/museum/photos/mostek_md_mainboard_1.jpg
  hardware:
  - title: ANALOG CARD
    subtitle: ''
    text: Analogue to Digital and Digital to Digital conversion card.
    image: /media/museum/hardware/mostek_md_analogboard_1.jpg
  oc_id: 819
  source:
    url: https://web.archive.org/web/20221205022457/http://www.old-computers.com/museum/computer.asp?c=819
    date: '2022-12-05'
---

The Mostek MD (from **M**icro **D**esign) marked the entry of Mostek Company in the computer business.\
It was a development system, aimed at promoting the family of Mostek boards, and built around several boards based on the 64 pin SDT bus.

The hearth of the system was the CPU board holding a Z80 (Mostek) processor, 10 KB of ROM and 8 KB of RAM. A large range of additional cards could be then added: dual Serial port, 32 KB RAM, Analogue/digital converter, 32-bit parallel port, and so on.

Using an ASCII video terminal, a basic one-board system allowed machine code programs to be assembled, debugged and run thanks to the built-in ROM monitor.

A complete system - like the one pictured - could manage two 8" floppy disc drives and run CP/M Operating System. However, these systems were mainly used for managing external devices in laboratories, universities and industry.

Special thanks to **John Jenkins**