From V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016) :
SPX
Sequenced Packet eXchange (Novell, Netware)
From The Free On-line Dictionary of Computing (30 December 2018) :
SPX
1. Sequenced Packet Exchange.
2. A graphics program for the Atari microcomputer.
ftp://src.doc.ic.ac.uk/computing/systems/atari/umich/Graphics/spx_v18.lzh)">(ftp://src.doc.ic.ac.uk/computing/systems/atari/umich/Graphics/spx_v18.lzh).
3. Simplex.
(1997-03-04)
From The Free On-line Dictionary of Computing (30 December 2018) :
spx
The filename extension for Screen
Peace eXtension files.
(1995-03-14)