Of all the changes to Apple's product lineup that took place on 15-Apr-92, the quietest was the departure of the Macintosh IIfx. The high-end Macintosh II offering has never quite fit into the product line, thanks to some engineering oddities and, of course, the eventual appearance of the Quadra series.
The IIfx remained on Apple's rolls this long probably because of its six NuBus slots as much as anything else. The initial '040 compatibility problems probably helped, but many users had commented that the Quadra 900's five slots weren't up to the heaviest tasks, making the IIfx, the last six-slot Mac, an important member of the Mac team.
When it was first introduced, the Mac IIfx was hailed as the "wicked fast" Macintosh by its fans within Apple. Its 40 MHz 68030 processor was more than twice as fast as the 16 MHz version found in previously "top-of-the-line" IIx and IIcx machines, and Apple's engineers boosted performance even further through the use of ASIC, or application-specific integrated circuit, technology. This ASIC technology provided coprocessors to handle mundane system tasks such as disk and SCSI activity and serial port communications, freeing the '030 to concentrate on computing.
Unfortunately, the IIfx created some compatibility problems with software that, contrary to Apple's recommendations, accessed hardware (such as serial ports or the disk controller) directly. A "IIfx Serial Switch" Control Panel alleviated the difficulties for applications and utilities that wanted to talk directly to the serial ports instead of working with the drivers, but other incompatibilities had to be ironed out by the application developers. Certainly this wasn't the fault of the IIfx, but the incompatibilities did leave a sour taste in many mouths, as did the special dual-ported memory and black SCSI terminator that only the IIfx required. It also didn't help that the IIfx's much-touted Direct Memory Access (DMA) abilities were never supported by the system software, making them useless except in theory.
The retirement of the IIfx leaves Apple with just two machines left in the five-year-old Macintosh II family: the IIci and IIsi, clocking in at 25 and 20 MHz, respectively. The Quadra 700 and 900, and the expected 950, fill the shoes of the ex-"wicked fast" IIfx.
Customers who still have the IIfx on order as of 15 April will have their orders filled, but Apple doesn't plan on taking further orders.