Understanding and Making a Retro-Computer Multi-ROM Switcher

In this video, I discuss the concept of a ROM-Switcher -- a device that lets you install an EPROM with several data/code images, and use an external switch to instruct your hardware on which ROM image to use. Such devices were common prior to cheap flash memory and are still used today in retro-computing projects.

The video covers the theory of how they work, includes the schematic of the "textbook" ROM-switching circuit, and then gives a tutorial and demo of preparing and using an EPROM with a ROM switching module in a Commodore computer.

Please use the following time-code index to jump to relevant sections in the video.

00:00 What is a ROM Switcher?
02:19 Theory: Using larger, compatible EPROMS
04:42 Theory: Access higher ROM pages
06:12 ROM switching circuit template
08:03 Applying circuit to other EPROM types
10:56 A note about pin compatibility
12:51 Overview of ROM switching module
15:21 Commodore Kernal Switching Demo Overview
16:16 Demo: Preparing EPROM image
17:52 Demo: Programming EPROM image
19:14 Demo: Switching kernals in a Commodore 16
22:08 Closing note

Purchase options for the featured multi-ROM switcher module and project GitHub page:
https://ebay.us/UgAkwz
https://github.com/SteveGuidi/video-c...


IC pinout drawings courtesy of Peter Schepers
https://ist.uwaterloo.ca/~schepers/ro...

Atari 2600 cartridge images courtesy of Atari Age
https://www.AtariAge.com

JiffyDOS ROM switcher image courtesy of Retro Innovations
https://store.go4retro.com