Alphacom VP42 Printer

  • The Alphacom VP42 is an 40-column thermal printer for the IEC bus. It is interesting because it contains a MOS 6500/1 microcontroller marked “VIC-42”.

    More photos can be found in this Flickr photo set.

    VIC-42 Chip

    On June 17, 2021, Bo Zimmerman started a discussion on the cbm-hackers mailing list because an electronics surplus dealer on eBay had been selling chips marked “VIC-42”. At the time, the “VIC-42” chip was unknown to the community. Various people speculated about the chip and what it could be. On June 20, “Six of DLoC” suggested that someone check the Alphacom 42 printer. An “Alphacom 42” printer was on eBay at the time, and it could be seen in the auction photos that it uses an 8041 microcontroller. However, David Wood asked me to check my printer, which is badged “Alphacom VP42”. I opened it up to my surprise, the “Alphacom VP42” did indeed contain the “VIC-42” chip. On June 21, I posted the news on cbm-hackers and on

    Upon seeing the VIC-42 in this printer, I immediately thought that it could be a MOS 6500/1 because the Commodore 1520 plotter uses one. I quickly did continuity checks and found that Vcc, Vss, and the crystal connections all matched the MOS 6500/1. Back in 2014, Jim Brain and members of cbm-hackers had developed a board to dump the firmware of the MOS 6500/1 in the 1520 plotter. I built a dumper based on this design. On June 26, I successfully used it to read the firmware out of the “VIC-42”, confirming that it is indeed a MOS 6500/1 microcontroller.

    “VIC-42” Firmware Dump (Binary, 2K)