• Type: Home computer
  • Released: 1984
  • Introductory price: ~$299
  • Discontinued: 1985
  • OS: Commodore BASIC 3.5
  • CPU: MOS 8501 @ ~1.77 MHz
  • Memory: 64 KB RAM
  • ROM: 64 KB (Commodore BASIC 3.5 with machine code monitor, and TRI-Micro’s “3 Plus 1” (word processor, spreadsheet, database, graphing))
  • Graphics: 160×200 (multicolor) / 320×200 (hires)
  • Text mode: 40×25 characters (PETSCII)
  • Palette: 121 colors
  • Sound: TED chip (2-channels)
  • I/O: Tape connector (incompatible with C64), cartridge slot (incompatible with C64), IEC port (compatible with C64), User port (for modems and nonstandard devices, incompatible with C64), Composite video connector including S-Video and mono audio signal, RF modulator

Released 1984: The “Plus/4” name refers to the four-application ROM resident office suite (word processor, spreadsheet, database, and graphing); it was billed as “the productivity computer with software built-in”. Internally, the Plus/4 shares the same basic architecture as the lower-end Commodore 16 and 116 models, and is able to use software and peripherals designed for them. It is not compatible with the well-established Commodore 64. The Plus/4 was the flagship computer of the 264-series. The Plus/4 had 64 KB of memory while the C16 and 116 had 16 KB. The Plus/4 had built-in software, whereas the others did not.

According to what I’ve understood from Bil Herd, ex. Commodore hardware engineer. A new management at Commodore after the leader Jack Tramiel left the company in 1984, misunderstood the 264-series and the Commodore 116. The Commodore 116 was the model ordered by Jack Tramiel before he left the company in 1984. It was meant to be a competitor for the marked segment of very cheap home computers that had emerged, in the price range 75-100 USD. The new management ordered the more expensive Plus/4 to be developed. When released, it stepped on the very successful Commodore 64’s toes in price range and confused the marked. It more or less landed on the Commodore 16 which was marketed and priced as something inbetween VIC20 and C64.

In total, 1 million 264 series machines were sold in its two years on the market. Of these, 400,000 were Plus/4s with most of the remainder being C16s. Beginning in 1986, remaining C16, C116 and Plus/4 inventories were sold at a much reduced price on the eastern bloc market, mainly Hungary. Hungary did not produce any home computers at the time, while the Soviet, Bulgarian and East German models were far too expensive for most Hungarians, and most Western models were completely out of reach. Thus, this move by Commodore was the first chance for many people in Hungary to own a computer. It created a fan-base that lasted well into the 1990’s and that contributed several unofficial ports of popular Commodore 64 programs. In Mexico, the C16 was sold as a beginners’ computer from early 1985 up to 1992.

My Commodore Plus/4 and repair

There was no display when I first got it. It’s a very common failure that either CPU or TED chip fails. The case is very small, and this results in heat that affects the reliability over the years. Those two chips was only used in the 264-series (C16, C116 and Plus/4), so they can be both difficult and a little expensive to come bye. I first replaced the TED chip, and it didn’t help. Then I replaced the CPU chip, and this time it worked. (CPU is probably the most common chip to fail and cause black screen, so I should have replaced that one first.) I also put heat-sinks on the chips before putting the machine back together.

SD2IEC floppy drive emulator works with this computer as well, only had to solder in a correct connector to take current from the cassette port. It got a different cassette port connector than the C64 and other Commodore 8-bit computers.

Commodore Plus/4

Remi Jakobsen

I'm collecting classic computers and video games, stretching from the 70's into the 90's. Restoration, history, usage ...

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2 thoughts on “Commodore Plus/4

  1. What all do you collect on the commodore.i have several things. Games joystick I think printer .I have 4 of the key boards plus/4 and other things. What are they worth. Dont no if any of it works or not..I dont no anything aboult them

    1. I’m interested in collecting and restoring everything from Commodore. Commodore is the main focus in my collection. The value depends on condition, tested and proven working or not, well kept, complete with original box, manual and everything is worth more.

      Printers are usually not very sought after. The Plus/4 unit itself is worth around 100 euro if it’s tested and working in good condition I would guess. Due to the small housing and heat problem, it’s very common with failed chips that could be a bit expensive and difficult to find.

      Can you send me some picture? My e-mail: remi@remimedia.com
      I could tell you more about what you got, maybe give you an offer if you want to sell something.

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