[mambodog]

Not sure about the machine but according to Romero[1] Quake (as with Doom) was developed on NeXTSTEP 3.3, which they continued to use, later running on Intel hardware, until 1996.

QuakeEd on NeXTSTEP: http://rome.ro/uploaded_images/qe_dev-726646.gif

[1] http://rome.ro/2006/12/apple-next-merger-birthday.html