On this day, 22 years ago, the #Rockbox project started, co-founded by me. We wrote an open source firmware for mp3 players. On its 10 year anniversary 2011, I wrote this:
https://daniel.haxx.se/blog/2011/12/07/ten-years-of-rockbox/
when we had get-togethers of #rockbox hackers, we did these (silly) towers of devices that could run Rockbox. Look at this beautiful example featuring 78 mp3 players.
More photos here: https://www.rockbox.org/wiki/TowerOfRockbox.html
@bagder OMG I totally recognize the beefy ones on the bottom layer with blue corners. They had full size disks in them and huge capacity.
@focusaurus yeps, a 20GB spinning 2.5" disk in there. 2MB of RAM that would be used to buffer mp3 in addition to run the actual OS and application
@bagder
The original 2MB buffer chip was already a bit small for 128Kbps MP3 and a HDD, but definitely too small for 320Kbps MP3 ripped from my CD 
Every time I played music, I remember thinking "when will the HDD die from all the power cycles ?" 
With a Compact Flash and IDE adapter, there is no spin-up time so it's not that bad.