Understanding and Making a Retro-Computer Multi-ROM Switcher

Рет қаралды 510

Күн бұрын

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:
ebay.us/UgAkwz
github.com/SteveGuidi/video-c...
IC pinout drawings courtesy of Peter Schepers
ist.uwaterloo.ca/~schepers/ro...
Atari 2600 cartridge images courtesy of Atari Age
www.AtariAge.com
JiffyDOS ROM switcher image courtesy of Retro Innovations
store.go4retro.com

Пікірлер: 6

@RDTengineered Ай бұрын

Great video. Gives me a clear piece of the puzzle. Wanting to do a 512 x 8 switcher with a 39040. A lot of old car ECUs used 27256 and 27512 eproms. Have to learn how to design the board now.

@richardpowell8198 3 ай бұрын

This is a great video I'm glad I found it this explains everything I needed to know 👍

@tadeusoares5648 Жыл бұрын

Thank you! I was in need of this info!

@greatwhiteretro 9 ай бұрын

One thing that wasn't clear, was you need to remove the jumpers for any address lines you plan to pass through ("D" mode), or you could short the address lines in question. It's shown clearly in the video, but wasn't described. Or maybe I missed it. But I was able to use a ST 27256 EPROM with two ROM images using this switcher once I found my mistake and corrected it.

@SteveGuidi 9 ай бұрын

Thank you for pointing this out! Yes, this is indeed the case with the module and schematic shown, but it was not mentioned explicitly.