What is "iapx"

In marketing, iAPX (Intel Advanced Performance Architecture with X standing in for the Greek letter χ (chi)) was a short lived designation used for several Intel microprocessors, including some 8086 family processors. Not being a simple initialism seems to have confused even Intel's technical writers as can be seen in their iAPX-88 Book where the asterisked expansion shows iAPX to mean Intel Advanced Processor System.

The iAPX prefix originally belonged to the Intel iAPX 432 architecture, alias Intel 8800. However, as this radical design failed in the marketplace, Intel also tried it on its more conventional 8086-family of processors, mainly used as a kind of system prefix but also to denote individual processors in the family. The 8086 based line was therefore called the iAPX 86 series for a few years during the early 1980s. This was abandoned rather soon, however. The industry around the 8088- and 80286-based de facto standard of IBM PC and IBM AT designs also seldom used that naming scheme. As a result, the iAPX prefix is now, again, more closely associated with the (non-x86) iAPX 432 architecture (which, although being a commercial failure, is often seen as historically important).