Since I often have to change the ROM when testing different software. I built a ROM simple switch.
You can find him here: https://github.com/hans61/gtrom
It supports a 27C4002, can be programmed with a TL866II and can switch between four ROM versions.
I'm also trying a switch with 27C160 and electronic switching for 16 ROMs. A little more patience.
Gigatron with quad ROM.jpg (270.14 KiB) Viewed 1685 times
I have tested a ROM switch with the 27C160 EPROM. The 27C160 can be programmed with a simple adapter via the TL866II. The 27C160 allows a selection of 16 ROM versions. The selected ROM is displayed with a 7 segment display (0..F). Switching is done by a push button. The switch is controlled by an ATtiny24 (alternatively 44/84). The last selected ROM is stored in the EEPROM (2 seconds delay) and automatically selected at power on. So a reset by power off/on is possible. The sources can be found here: https://github.com/hans61/gtrom16
rom-switcher-16-1.jpg (543.85 KiB) Viewed 1624 times
rom-switcher-16-2.jpg (455.62 KiB) Viewed 1624 times