Editing DEC PRISM (section)

===Background===
Introduced in 1977, the [[VAX]] was a runaway success for DEC, cementing its place as the world's #2 computer vendor behind [[IBM]]. The VAX was noted for its rich [[instruction set architecture]] (ISA), which was implemented in complex [[microcode]]. The VMS [[operating system]] was layered on top of this ISA, which drove it to have certain requirements for [[interrupt]] handling and the memory model used for [[memory paging]]. By the early 1980s, VAX systems had become "the computing hub of many technology-driven companies, sending spokes of RS-232 cables out to a rim of VT-100 terminals that kept the science and engineering departments rolling."{{sfn|Comerford|1992|p=26}}

This happy situation was upset by the relentless improvement of [[semiconductor manufacturing]] as encoded by [[Moore's Law]]; by the early 1980s there were a number of capable [[32-bit]] single-chip [[microprocessor]]s with performance similar to early VAX machines yet able to fit into a desktop [[pizza box form factor]]. Companies like [[Sun Microsystems]] introduced [[Motorola 68000 series]]-based [[Unix workstation]]s that could replace a huge multi-user VAX machine with one that provided even more performance but was inexpensive enough to be purchased for every user that required one. While DEC's own microprocessor teams were introducing a series of VAX implementations at lower price-points, the [[price-performance ratio]] of their systems continued to be eroded. By the later half of the 1980s, DEC found itself being locked out of the technical market.{{sfn|Comerford|1992|p=26}}