This is the ColecoVision low-power System Memory and BIOS ROM replacement module. Integrating a 24KB SRAM upgrade and Flash ROM to replace your onboard main system memory and EPROM. This sits in between your Z80 and mainboard. If you have an SGM expansion module, this will not conflict with it.

To install, you will need to remove your old EPROM and two RAM memory chips (either desolder or cut legs and use a soldering iron to remove legs individually) and then desolder the Z80 carefully. You may install a DIP-40 socket for this module or directly solder in place. If you socket the 74138 to the left of the Z80, the Z80 will require a socket as well for this module to fit correctly. You will need four short wires to connect to the aforementioned 74138 (as shown in photos) with easy-to-remember numbered pins on the left side of this module. Specifically, pins 12,13,14,15. Solder the top of those legs with a small dab to whet it and prepare for easy soldering of the wire. Wires are typically 1" in length (2.0 to 2.54cm) and only the tips need their insulation removed. If both chips are socketed, it will be easy to remove the pair together with this length of wire.

This module has three jumpers for selecting which BIOS. We only have three to choose from -- Original, no-delay, and the "different font" with standard delay. As such, only the two right-most jumpers are necessary but as this has a large Flash ROM (SST39SF010A) three are necessary (A13, A14, A15), while the three upper addresses (A16, A17, A18) are grounded so a SST39SF040 is compatible but those addresses are inaccessible. You may reprogram this Flash chip with your own BIOS if you choose. Flash chip will be pre-programmed and included with every order.