Anyway, the Commodore 64 famously had a usable 39kB, because the rest of the addressable memory space was usually occupied by the BASIC interpreter / OS (much the same thing on that machine).
However, neither of those numbers is strictly true, as some developers paged in (kinda sorta) the 4kB RAM allowed to the I/O system -- effectively turning the machine into a 68kB box.
Fun times.
Not extra RAM in the sense of paging to disk, but in the sense of (ab)using the RAM in the disk drive?
Wikipedia said the most common model had the same CPU chip as the C64 and 2kB RAM.
EDIT: https://www.lemon64.com/forum/viewtopic.php?t=27911 says yes, and lists a few demos. https://www.reddit.com/r/c64/comments/iw2ubd/can_you_use_the... might also be interesting.
I think the 1541 transfer speed only ever felt truly fast to people who'd experienced years of using the 1530 (the cassette tape storage device).
Outside of demos, the most interesting suggestion was to offload data(base) querying logic to the drive.
> I had the smaller one a generation prior to the c64