In above posting
https://forum.arduino.cc/index.php?topic=417851.msg2883182#msg2883182
up to 80KB of 96KB memory made logic analyzer like reading at 28Msps possible, and the only restriction was the size of RAM that could be used for that.
Lately using RAM (disk) in a completely different application scenario on a different microcontroller saved the day again and allowed for stuff otherwise impossible.
On a (5$) Raspberry Pi Zero there is a 188MB ("only") /dev/shm ramdisk. I used that to capture video frames at much higher framerates than Raspberry "raspivid" allows for (90fps). The higher framerates became possible by reducing framesize and thus increasing framerate. The 188MB allowed to capture up to 8s of high framerate video regardless of resolution.
Here is a sample (640x128 stretched) video, captured at 665fps(!).
The animated .gif plays at 25fps, 26.6 slower than real:
Here are the framerates that can be a achieved with 5$ camera:
Summary:
Two completely different problems, solved by making (extreme) use of (limited) RAM.