Gecko's CPU Library

Motorola 68060 processors

Introduction: 1994

The 68060 (usually referred to simply as the 060, pronounced oh-sixty) is not just a redesign of the 68040, but a from-scratch entirely new processor, adding a second integer pipeline, a two cycle integer multiplication unit, a faster FPU, and branch prediction logic. It has 2 to 3 times the performance capability of the 68040 at the same clockrate. The 68060 design was led by Joe Circello.

The 68060 shares most architectural features with the original Pentium. Both have a very similar superscalar in-order dual instruction pipeline configuration, and an instruction decoder which breaks down complex instructions into simpler ones before execution. However, a significant difference is that the 68060 FPU is not pipelined and is therefore up to three times slower than the Pentium in floating point applications. In contrast to that, integer multiplications and bit shifting instructions are significantly faster on the 68060. An interesting feature of the 68060 is the ability to execute simple instructions in the address generation unit (AGU) and thereby supply the result two cycles before the ALU. Another point of interest is that large amounts of commercial compiled code were analyzed for clues as to which instructions would be the best candidates for performance optimization.

The 68060 was the last development of the 680x0 series for general purpose use, abandoned in favour of the PowerPC chips. It saw use in some late-model Amiga machines and Amiga accelerator cards as well as some Atari ST clones and a Falcon accelerator board (CT060), but Apple Inc. and the Unix world had moved onto various RISC platforms. The 68060 was introduced at 50MHz on Motorola's 0.6 m manufacturing process. A few years later it was shrunk to 0.42 m and bumped to 66MHz and 75MHz. The 0.42 m parts were rare, as Motorola decided to concentrate on their PowerPC RISC project. Should Motorola have decided to stick with the 680x0 series it is very likely that the next processor would have resembled Intel's P6 architecture.

The 68060 was also used in Nortel's Meridian1 Option 51, 61 and 81 large office PBX systems, powering the CP3 and CP4 core processor boards. A pair of these boards each sporting a 68060 could be used to make the PBX fault tolerant. This was a logical application as previous Meridian1 cores used other Motorola chips. Nortel has since changed the architecture to use Intel processors.

Developments of the basic core continue, intended for embedded systems. Here they are combined with a number of peripheral interfaces to reduce the overall complexity and power requirements of a design. A number of chips, each with different sets of interfaces, are sold under the name ColdFire and DragonBall.

Source: Wikipedia, the free encyclopedia.