I had the XL and XE's.
I made my own PCB and had an external box with 1MB of RAM,IBM controller with a 40MB IBM HD,variable 99-9601 baud modem on my ATARI 128.
Emulation boot disks let me run Commie-door/ATARI/IBM software.
Bad ass 8 bit times!
Latter I had some inter connected ATARI Jaguars (16 bit).