I worked for Cray Research in the 1980s. A lot of the CAD software for the Cray 2 ran on a Z80 based CPM machine called the Intertec Suberbrain. Then we got a bunch of PCs from ATT called the ATT 6300 (Actually made by Olivetti). We figured out that if we replaced the 8086 in the ATT 6300 with a NEC V20, we could run all the Z80 software on the ATT 6300 by putting the V20 into Z80 compatibility mode. Saved a lot of work and time for us.