[blihp]

Several important DOS applications (spreadsheets, databases, CAD etc... even Doom required 4 Meg) were absolutely able to use more than 640k which was why you saw PCs with more memory: there were applications people cared about that needed it then. Granted, it was a painful business that had all sorts of limitations but the use cases were there. Anyone paying attention could look around and see that this problem had already been solved in better ways on other platforms and the various DOS multitaskers were just stop-gaps until a more universal solution (both OS and application) came along.

[eatfish]

True, and I think Quarterdeck (and Pharlap, Rational, etc.) developed the VCPI specification that allowed those DOS extenders to work cooperatively. Some of the early DOS extenders took over the entire machine and did not allow that.