Ancient history few people know. AutoCAD started life as a CP/M application. When you bought ACAD you had to buy an 8087 math co-processor card as well as a 512K RAM drive card.

I ran ACAD for many years on such a system using a DEC VT-100 terminal, an early magnetic tablet with a wired puck having a coil for pickup and a large CRT-based graphics monitor. Memory restrictions were such that you had to do things like unload modules from memory before plotting and write clever code in Lisp to use less memory while drafting. Cool stuff.