TRS-80 Model 4 (Gate Array Version) ROM B/C EPROM Adapter

This board allows a 2764 EPROM to be plugged into the ROM B/C socket (U4) of a TRS-80 Model 4 computer. It is applicable to the gate array version only, which is easily identified by noting the orientation of the RS-232 serial port connector. That connector will face towards the rear of the gate array version computer, or downwards on a non-gate-array version computer.

ROM B/C is an MCM68A364 mask-programmed ROM, and it is not pin-compatible with common 2764 EPROMs. This board adapts the pinout, and also allows the original mask-programmed ROM to be reinstalled and selected with a jumper or remote switch.

The primary motivation of this project is to support the new auto-boot menu feature of the FreHD hard disk emulator without requiring soldered modifications of the computer itself, and also allowing the original ROM to be selected when desired.

Design files for this project may be found at:

https://github.com/NF6X/M4-GA-ROM-BC

Additional information may be found at:

http://www.nf6x.net/tag/M4-GA-ROM-BC

M4-GA-ROM-BC is a free hardware design: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

M4-GA-ROM-BC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with M4-GA-ROM-BC. If not, see http://www.gnu.org/licenses/.