Motorola 68040

The Motorola 68040, also referred to as the 68040 or '040, is a 32-bit CISC processor that was produced by Motorola's Semiconductor Products Sector, superseding the Motorola 68030. The 68040 was used in the Centris, Quadra, and PowerBook 500 series. It was also used in the NeXTcube and NeXTstation computers. It was the last of the 68k processor series to be used by Apple Computer, which instead migrated to PowerPC processors for its Power Macintosh line.

Features
Introduced in 1990, the 68040 improved processor performance over the 68030 by increasing the instruction and data caches eight-fold to 4 kilobytes each. Instruction pipelining was doubled to 6 stages. The internal core operated at twice the speed of the external clock, so Apple sometimes marketed versions with two clock speeds, such as 66/33MHz.

The 68040 was available in external clock speeds up to 40MHz in a ceramic pin grid array (PGA) package. However, heat became a factor in the design and a 50MHz version was cancelled. The compact quad flat package (QFP) version was delayed for Apple's PowerBook 500 series and limited to 33MHz.

Variants

 * Motorola 68LC040 - a low-cost version without a built-in floating-point unit. Mostly used in entry-level and portable Macintosh models. Units with mask numbers lower than 03E23G (manufactured before late 1994) contain a bug which breaks software emulating a floating-point unit, such as SoftwareFPU. These defective units were found in many early Macintosh LC 475s and Quadra 605s. Patrick Fleming of Apple Computer reportedly denied the existence of the bug, but Motorola confirmed it as bug E4 in revision 4 of their official 68LC040 errata sheet.
 * Motorola 68EC040 - a lower-cost embedded version without built-in floating-point nor memory management units. Not used by Apple in any model.

Macintosh models with 68040 processors
68040 pin grid array (PGA) version: (with FPU) 68LC040 pin grid array (PGA) version: (no FPU) 68040 Quad flat package (QFP) version: (with FPU) 68LC040 Quad flat package (QFP) version: (no FPU)
 * Macintosh Centris 660AV/Quadra 660AV (25/25 MHz)
 * Macintosh Quadra 610 (25 MHz)
 * Macintosh Quadra 630 (33 MHz)
 * Macintosh Quadra 650 (33 MHz)
 * Macintosh Quadra 700 (25 MHz)
 * Macintosh Quadra 800/840AV (33/40 MHz)
 * Macintosh Quadra 900/950 (25/33 MHz)
 * Macintosh Centris 610 (20 MHz)
 * Macintosh Centris 650 (25 MHz)
 * Macintosh Quadra 605 (25 MHz)
 * Macintosh LC 475 (25 MHz)
 * Macintosh LC 575/580 (33/33 MHz)
 * Macintosh LC 630 (33 MHz)
 * Macintosh Performa 475 (25 MHz)
 * Macintosh Performa 575/580 (33/33 MHz)
 * Macintosh Performa 630/640 (33/33 MHz)
 * PowerBook 550c (33 MHz)
 * PowerBook 190 (33 MHz)
 * PowerBook 520/540 (25/33 MHz)
 * PowerBook Duo 280/280c (33/33 MHz)