Motorola 68040

Motorola 68040 is one CISC 32 of the family m68k of . It succeeds and precedes it (the 68050 was a given up project, it was to the 040 what were the 030 to the 020, a finer engraving, and masks more important). This processor is often called 040.

The 68040 is the first member of the family 680x0 with built-in arithmetic coprocessor. It includes all the functionalities which were formerly external, namely itcalculating unit in floating point and MMU (which was added in the 68030). It also has masks separate of instructions and data of 4 kilobytes each one. It is entirely pipeliné, with six stages.

The FPU in the 68040 was unable to use the functions transcendentales IEEE which were supported by Motorola 68881 and 68882. The software of support of floating point of Motorola (FPSP) emulated these instructions in the form of interruptions. As it was a treatment by exception, the abuse functions transcendentales caused serious decelerations.

Heat was a problem during all the life of the 68040. Whereas by cycle of clock it provided the double of performance from already old the 68030, the complexity of the chip and the power supply necessary to feed great surface and large the masks caused an accumulation of heat. This affected the capacities of evolution of the processor and it never passed the bar of the 40 MHz. An alternative with 50 MHz was envisaged, but abandoned. The first overclockeurs succeeded however with radiators and ventilators (exceptional for the time).

The 68040 were competitorINTEL 80486 but were exceeded by him at an equivalent frequency.

Various versions were used in the series of computers and APPLE Macintosh Quadra, like in a certain number of workstations and of the later versions of .



The 68LC040 is one 68040 without FPU.


The 68EC040 is one 68040 without FPU nor MMU.

Uses of the 68040


For very many model of its range of , in particular them Macintosh Centris and Quadra, of Performa and of .


For the micro-computer Amiga 4000.


For NeXTstation.

List Motorola microprocessors

6800 · · · · 68010 · 68012 · 68020 · · 68040 · · 88000 · · ColdFire · · · PowerPC G4

FPU : 68881 · 68882

: DSP560XX · DSP563XX · DSP566XX · DSP568XX · DSP96XXX


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