VIC-20 Expansion Port Breakout

Last modified: Sep 19, 2022,  Page views: 30

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Categories: hobbyist
Compatible: VIC-20
Price: $19.00
How to Order: Order from Dorktronic's ebay listing: VIC-20 Expansion Port Breakout.
Documentation: Not included
VIC-20 Expansion Port Breakout with breadboard

Port Breakout with breadboard

VIC-20 Expansion Port Breakout, top view

Port Breakout, top view

VIC-20 Expansion Port Breakout, bottom view

Port Breakout, bottom view

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My Take

A lot of people today who love Commodore 8-Bit computers enjoy them for their hackability. This board is one of a host of similar hobbyist products that make prototyping, hacking and exploring the electronics side of the computer much easier.

A breakout board is one that allows the computer to continue functioning normally, while exposing the lines of some port or IC socket to the electronics hobbyist, with minimal fuss. This particular breakout board plugs into the VIC-20's wide expansion port, and has labeled downward-facing pins that line up with the pin spacing on a standard prototyping breadboard.

The +5 VDC and Ground lines from the expansion port lead to pins which are inserted into the power rails on the outside edge of the breadboard, and the rest extend a bit further to plug into the main inner section of the breadboard. A handy reset button is built in, connecting the expansion port's reset line to ground.

You should not attempt to use one of these breakout boards, unless you are well versed in electronics and know what you're doing. Any damage you cause to your computer will be your own fault.

It's an incredibly handy board for doing quick prototype or tinker jobs. jbevren, January 2018

Example Usage for Prototyping

David Wood, also known as Jbevren on IRC, picked up one of these at a computer show. He has been using it to prototype an EEPROM Shadow Rom. The KERNAL rom from inside the computer has been pulled, and inserted into the first breadboard. The breakout board connects the breadboard to the VIC-20's expansion port. The only additional line from the computer required for his project is the black wire that can be seen sneaking out the corner of the expansion port. That line is inserted into the Chip Select pin hole of the KERNAL rom's socket on the mainboard.

Looks like Retro Fun!

VIC-20 EEPROM Shadow Rom, prototyped on breakout board

In this next photo, the final version of the project can be seen. It is the tiny yellow board into which the KERNAL rom is plugged, near the front right of the mainboard, with 5 colorful lines coming off it.

VIC-20 EEPROM Shadow Rom, final version

Want to support my hard work? Here's how!


BRAND NEW Commodore VIC-20 Expansion Port Cartridge breadboard breakout with Reset Pushbutton Switch. Easily prototype your VIC-20 expansion port project without soldering!

NOTE: Pictured breadboard is not included.

Board Features:

  • *UPDATED* Gold plated contacts
  • *UPDATED* Machined header pins
  • 80mm (3.2") in height X 100mm (3.9") in width.
  • This board is designed to plug into a SOLDERLESS BREADBOARD for easy no-soldering prototyping.
  • Simply plug the adapter into your breadboard and you are ready to connect it to your Commodore VIC-20!
  • At the top of the board, ALL of the expansion port pins are connected to an easy-to-access header. Ready to use.
  • +5V (VCC) and Ground (GND) points are aligned to plug into your breadboard's power bus bar.
  • Crisp, easy-to-read silkscreen describes each pin's function. See pics!
  • The board features a reset pushbutton switch. The reset switch is routed to the RESET line and ground.
  • Insert the adapter into your expansion port with reset switch facing upwards.