"Wicked fast" entered the Macintosh vocabulary when Apple rolled
out the 40MHz IIfx in March 1990. This was the Mac of choice for
graphic designers, offering nearly three times the performance of the
IIx, thanks to a lightning fast CPU, an
improved memory architecture, and special DMA chips which relieved
the CPU of much of its I/O burden. A built-in 32KB static RAM cache
also helps boost performance.
The IIfx requires a special "black" SCSI terminator to accommodate
its unusual architecture.