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The TIM (Terminal Interface Monitor) was a MOS Technology Inc's build-it-yourself 6502 development system that was launched before the 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.

Please consider donating your old computer / videogame system to or one of our partners from anywhere in the world (Europe, America, Asia, etc.).


Hi, I am a vintage computer collector. Please contact me (E-Mail via my website) if you have a TIM to offer.

Sunday 12th September 2021
Achim Baqué

I am looking for a MOS TIM for my collection. Any offer welcome.

Thursday 3rd March 2016
Achim (Germany)

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.

Friday 4th April 2003
Brian Bagnall (Canada)
Commodore Retro


TYPE  Home Computer
YEAR  1975
BUILT IN LANGUAGE  ROM based hex monitor
KEYBOARD  external 8-level ASCII terminal or teletype
CPU  6502
SPEED  1 Mhz.
RAM  1024 bytes (depending of the user)
ROM  1024 byte TIM monitor in 6530, 1024 byte in 2708 EPROM
SIZE / WEIGHT  Implementation specific
I/O PORTS  Front 2708 eprom burner, BNC analog output, rear RS232
BUILT IN MEDIA  2708 in front socket can be written (programmed) and read
OS  Monitor in 6530, user code in the internal 2708 EPROM
POWER SUPPLY  User built
PRICE  unknown

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