RAM Doubler really did work, and did it with a surprisingly low footprint. I usually stuffed my classic Macs so full of RAM that virtual memory of any kind wasn’t needed, but for systems with hard low ceilings like the PowerBook 1400 or the Power Mac 6400/6500/TAM, RAM Doubler was far superior to Apple’s built-in virtual memory. With RAM Doubler, Classilla could actually start and be stable on my 1400. Without it, well …
It came back in Linux as ‘zswap’ and then ‘zram’: https://en.wikipedia.org/wiki/Zram
It was actually useful on early Android phones, which tended to have 256MB of RAM and really needed 1GB, or had 1GB and really needed 2GB. These days 4GB is pretty normal and 16GB is available on some flagships.
I just ran into those trying to use a Raspberry Pi 4 as a desktop computer. Even with 4GB of RAM lots of folks recommend using one of these. It doesn’t help that the default SD storage on RPi is very very slow; swapping to it is not a good idea at all.
an external USB 4 SSD drive is much faster than the built in MicroSD…
On those early PowerMacs, RAM Doubler and Speed Doubler felt like miracles in some cases. (Speed Doubler was a collection of gadgets, IIRC, which I think included an improved 68k emulator and an improved disk cache.)
I think a precipitous drop in RAM prices, maybe early ’96 or so, likely had as much to do with killing RAM Doubler as any kind of improvements to virtual memory on Mac. At some point around then, I went from not being able to afford the RAM I needed to being able to buy as much as my Mac could use.
MacOS sort of had virtual memory starting with System 7.0 in 1991, but the implementation was terrible and performance was so bad no one used it. Then an Apple engineer whose name I forget (Jim something) profiled it and found all sorts of optimizations, which went into 7.5.
The windows version of this (which didn’t work) was on lobsters a few months ago: https://lobste.rs/s/x4jxxn/inside_story_outside_investigation
I have no idea whether the Windows version of this product worked or not, but the story you linked is not about that. It is about a competitive, contemporaneous product from Syncronys called “SoftRAM”, not Connectix RAM Doubler.
Modern Windows and Mac OS have memory compression built in and enabled by default now. Linux sort of does in that you can swap to compressed memory using zram but I’m not sure how often this is turned on.