Motorola 68060

The 68060 was launched in April 1994, with Joe Circello as architect. By then Apple had already announced the move to PowerPC, developed by IBM and by Motorola itself, and the Unix workstation market was moving to RISC processors. No Macintosh used the 68060.

There was no 68050. It was planned at one point inside Motorola, but the family jumped straight from the 68040 to the 68060.

It has 2.5 million transistors and is superscalar: it has two integer execution pipelines, of four stages each, and can execute in each cycle two integer instructions (or one integer and one floating-point) plus a branch. Behind the scenes, the 68000's complicated instructions are converted into a simpler, fixed format before entering those pipelines.

The caches grew to 8 KB of instructions and 8 KB of data. There is a branch cache with 256 entries, which lets most branches cost zero cycles, because the processor already knows where it is going before it gets there.

To save silicon, some little-used instructions were dropped from hardware: MOVEP, CHK2, CMP2, CAS2, CAS with misaligned data and the 64-bit multiplications and divisions. When they turn up, the processor raises an exception and a software package does the job. The same happens with some of the FPU's functions.

The core runs at 3.3 V and talks to both 3.3 and 5 V chips. The bus is compatible with the 68040's, which makes boards easier. Motorola sold it at 50 and 66 MHz, and the 68EC060 also at 40 MHz. It started on a 0.6 µm process and was later shrunk to 0.42 µm. It comes in a 206-pin ceramic PGA.

As with the 68040, there are two cheaper versions: the 68LC060 has no floating-point unit but keeps the MMU, and the 68EC060 has neither. They are used mostly in embedded equipment.

In integer multiplications and bit shifts, the 68060 is considerably faster than the Pentium of the same era. In floating point it is weaker: the FPU isn't pipelined and can be up to three times slower.

With no Macs, the 68060 went into professional equipment: Nortel Meridian 1 telephone exchanges, routers from Wellfleet and Cisco, and Chyron television character generators.

In the retro world, it gave new life to several platforms: the CT60 and CT63 boards for the Atari Falcon, the Atari-compatible Medusa Hades 060, and the Q60, a successor to the Sinclair QL.

None of Commodore's Amigas left the factory with a 68060. Only after the bankruptcy did Escom sell a version of the A4000T with a 68060 at 50 MHz.

Where the 68060 shone was in accelerators: the Blizzard 1260 for the A1200 trapdoor, the Blizzard 2060 for the A2000 and the CyberStorm 060 for the A3000 and A4000, all from Phase 5. They remain among the most sought-after boards, and some manufacturers still make new 68060 boards today.

AmigaOS needs 68060.library, which normally comes with the board, to handle the instructions the 68060 no longer has in hardware. Without it, many programs crash as soon as they start.