SPLD-based replacement of the Compaq Portable RAM decoder PROM (U35). The adapter PCB is arranged so the first slot isn't blocked due to the height of the socket+IC. Allows 640K RAM (64+64+256+256) on the system board. With jumper for stock 256K mode (64+64+64+64). Check the third picture to ensure you have the applicable Board Version 1. You also need at least BIOS Revision C, in either one or two chips (matching the number of chips your board currently has). Source files