HP11C ++

[Dave Britten]

Quite intriguing. I'd be reluctant to open up any of my 11Cs and 15Cs and start moving chips around to see what happens, but this might be something that could be experimented with using an emulator to find out if the 11C ROM does indeed support additional memory. The 42S can be upgraded from 8 KB to 32 KB by simply swapping the SRAM chip and closing a jumper on the PCB to tell the "OS" to use more RAM, so maybe something similar is possible in the 11C!

It's also worth mentioning that Swiss Micros has a special firmware for their DM15L that provides additional memory (can't remember how much, but it's enough that I'm tempted to order one). Figuring out how they patched the ROM and/or emulator for that model might be a good place to start.