Motorola 68040

Motorola 68040. The Motorola 68040 is a 32-bit microprocessor from Motorola, released in 1990 as the successor to the Motorola 68030. It was a highly integrated design, incorporating a floating-point unit and separate instruction cache and data cache on-die, which significantly boosted performance for workstation and personal computer systems. The processor was widely used in a variety of platforms during the early 1990s, including those from Apple Computer, NeXT, and Amiga.

Overview

Introduced at the dawn of the 1990s, the 68040 represented the peak of CISC design within the Motorola 68000 series. It was positioned as a high-performance CPU for demanding computing environments, competing directly with contemporary RISC processors like the Intel i860 and Sun's SPARC architecture. The chip's release was a significant event for the computer industry, particularly for the Apple Macintosh platform, where it powered the transition to more powerful Quadra and Centris model lines. Its integration of key components previously handled by separate coprocessor chips made it a cost-effective and powerful solution for system designers.

Design and features

The 68040 featured a superscalar pipeline capable of issuing multiple instructions per clock cycle, a first for the 68000 family. It contained two 4 KB caches, one for instructions and one for data, implementing a Harvard architecture model on a single chip. The on-chip floating-point unit eliminated the need for an external 68881 or 68882 FPU, though its performance, while compliant with the IEEE 754 standard, was sometimes criticized in comparison to dedicated units. The memory management unit included a translation lookaside buffer for efficient virtual memory support, and the bus controller supported synchronous protocols for interfacing with RAM and ROM.

Variants

Several variants of the 68040 were produced to address different market needs and thermal constraints. The standard 68040 (often labeled 68040) included a full FPU and MMU. The 68LC040 was a lower-cost version that omitted the floating-point unit entirely, used in systems like the Apple Macintosh LC III. The 68EC040 ("Embedded Controller") omitted both the FPU and MMU, targeting the embedded system market. A 68040V was a 3.3-volt version designed for lower power consumption. Furthermore, Motorola and third-party companies like IBM produced derivatives and compatible chips for specific applications.

Applications and usage

The processor found its most prominent home in Apple's high-end Macintosh computers, including the Macintosh Quadra and Macintosh Centris series, as well as the PowerBook 500 series. It was the central CPU for the NeXTcube and NeXTstation systems from NeXT. In the Amiga world, it was used in accelerator cards for the Amiga 1200 and Amiga 4000, and was the native processor for the Amiga 4000T. Other notable uses included Unix workstations from HP, Texas Instruments, and Silicon Graphics, as well as in embedded systems, laser printer controllers, and military avionics.

Legacy and successors

The 68040 was the last full-featured design of the mainstream 68000 line before Motorola shifted focus to the PowerPC alliance with IBM and Apple. Its direct successor, the Motorola 68060, offered higher clock speeds and improved pipelining but was produced in smaller quantities as the industry moved towards RISC. The 68040 architecture lived on in the embedded system market for many years, with its design philosophy influencing later microcontroller families. Its role in powering iconic computers from Apple, NeXT, and Commodore International secures its place in the history of personal computing.

Category:Motorola microprocessors Category:68000 microprocessors