website/content/museum/mos-technology-tim.md

---
title: MOS TECHNOLOGY TIM
categories:
- Computers
types:
- Home Computer
origins:
- U.S.A.
years:
- '1975'
cpus:
- '6502'
params:
  name: TIM
  company: /companies/mos-technology
  company_name: MOS TECHNOLOGY
  specs:
  - label: NAME
    value: TIM
  - label: MANUFACTURER
    value: MOS Technology
  - label: TYPE
    value: Home Computer
  - label: ORIGIN
    value: U.S.A.
  - label: YEAR
    value: '1975'
  - label: BUILT IN LANGUAGE
    value: ROM based hex monitor
  - label: KEYBOARD
    value: external 8-level ASCII terminal or teletype
  - label: CPU
    value: '6502'
  - label: SPEED
    value: 1 Mhz.
  - label: RAM
    value: 1024 bytes (depending of the user)
  - label: ROM
    value: 1024 byte TIM monitor in 6530, 1024 byte in 2708 EPROM
  - label: SIZE / WEIGHT
    value: Implementation specific
  - label: I/O PORTS
    value: Front 2708 eprom burner, BNC analog output, rear RS232
  - label: BUILT IN MEDIA
    value: 2708 in front socket can be written (programmed) and read
  - label: OS
    value: Monitor in 6530, user code in the internal 2708 EPROM
  - label: POWER SUPPLY
    value: User built
  - label: PRICE
    value: unknown
  tabs:
  - photos
  photos:
  - title: 'SYSTEM #1'
    subtitle: ''
    text: ''
    image: null
  - title: 'SYSTEM #2'
    subtitle: ''
    text: System with MOS manuals
    image: null
  - title: FRONT PANEL
    subtitle: ''
    text: |-
      A minimalist version!

      **(1)** Power supply status\
      **(2)** LEDs under program control\
      **(3)** Vents for cooling!\
      **(4)** 3-position switch. Sets which memory device will be mapped to top memory upon next reset (6502 vectors in top memory) usually with application code.\
      **(5)** Reset switch\
      **(6)** BNC connector. Analog/Digital converter output\
      **(7)** 2708 EPROM on ZIF socket. Only 2708 version could be programmed
    image: null
  - title: EPROM BURNER
    subtitle: ''
    text: |-
      **(1)** Zero Insertion Force (ZIF) socket for 2708 EPROM\
      **(2)** 2708 Eprom programmer circuitry. Software routines are contained in the internal Eprom, allowing copy 2708 into ZIF socket to internal RAM or program external 2708 from data in RAM.
    image: null
  - title: MOS CHIPS AREA
    subtitle: ''
    text: |-
      **(1)** 6502 processor. When initially built, this board used a 6502 without the ROR instruction. There were enough complaints that MOS technology added it. This 6502 was replaced when the new version became available\
      **(2)** 6530-004. This IC contains 64 bytes of RAM, 1024 bytes of ROM (TIM monitor), a timer and 16 I/O lines.\
      **(3)** 2 x 6532 general purpose I/O chips. Each had 128 Byte RAM, a timer and two 8-bit bidirectional ports.
    image: null
  - title: ROM AND RAM
    subtitle: ''
    text: |-
      Internal 2708 EPROM. Contains utility subroutines, eg Burn EPROM.\
      Note the three high stacked RAM chips! Each one is 2114 - 1024 x 4 bit. Chip select pins on other side are only pins not common to all three layers.
    image: null
  comments:
  - author: Achim Baqué
    date: Sunday 12th September 2021
    text: Hi, I am a vintage computer collector. Please contact me (E-Mail via my website) if you have a TIM to offer.
  - author: Achim (Germany)
    date: Thursday 3rd March 2016
    text: |-
      Hi,\
      I am looking for a MOS TIM for my collection. Any offer welcome.\
      Thanks
  - author: Brian Bagnall (Canada)
    date: Friday 4th April 2003
    text: Great information on a relatively unknown computer. Any idea which month in 1975 it was released and how MOS went about marketing it? I haven't been able to find anything about TIM in my old Byte mags.
  oc_id: 747
  source:
    url: https://web.archive.org/web/20230402080022/http://www.old-computers.com/museum/computer.asp?c=747
    date: '2023-04-02'
---

The TIM (Terminal Interface Monitor) was a MOS Technology Inc's build-it-yourself 6502 development system that was launched before the [KIM-1](/museum/mos-technology-kim-1/).

When a computer fan ordered a TIM from MOS Technology in Norristown, Pennsylvania, he got a MCS6530-004 (1k TIM monitor program in ROM), and a manual (15 sheets of 11x17 folded & stapled in the middle) containing a suggested schematic, the TIM monitor commands, and listing. He had to provide himself with various components, including the MOS MSC6502 processor.

Thanks to **Jeffrey R. Owen**, the owner of the pictured system, who relates us:\
When the KIM-1 was announced in 1975, my order was immediately placed. The price was US$150. I received a KIM-1 with serial number 285. The 6502 at that time did NOT have the ROR instruction.

About a year later, seeking more flexibility and wanting to use the newly added 'ROR' instruction, I purchased a TIM,an MCS6502 with the 'ROR' instruction, and two MCS6532's.

I constructed a simple computer, much like the one in the TIM manual, on a kludge board. No box, it was powered by a lab supply. Features and circuits were added, and removed as required. Mounting it in the brown box with power supply was done in 1979, oneof the last modifications. It was then a small development system including a 2708 PROM burner (ZIF socket outside box), and a three position switch selecting the memory map presented after reset.

I gave my KIM-1 to a friend in Teheran when we left Iran in September 1978. I kept the TIM which was just a circuit board at the time. We left Iran by taking a train to Moscow, then another to Belgium. When leaving the USSR, the customs officer looked at the board, and called a specialist, who quickly identified every chip and indicated that there was no problem.

Long after it had ceased to be a development system, the TIM served as a printer switch, allowing three computers to share a printer, and using A 2708 EPROM containing the printer switch application code in the ZIF socket.