[becurious]

There was a program called Switcha published as a listing in Your Sinclair. You could make a 48K Sinclair Spectrum appear as three 16K machines. It installed an interrupt mode 2 handler and checked for a key combination to swap out the lower 16K of RAM. No reason it couldn’t have time sliced them.

[JNRowe]

What a time to be alive, 1980s pdf at your fingertip¹. The tool is described on page 84 of the linked doc.

¹ https://ia903206.us.archive.org/19/items/Your_Sinclair_003/Y...

[becurious]

Thanks! I remember that cover now! The article has both the hex and the asm listing. I think I did an update to it to use the bank switched memory on the 128K to get 8 16K Spectrums.

Of course with something like a MGT +D with the 8K ROM and 8K SRAM it would have been possible to use the NMI button to switch between two 48K Spectrums on a 128K and have them run a game in one and BASIC in the other.