CPUs: Motorola 68060

If you’ve never heard of the Motorola 68060 CPU, there’s a good reason for it. Apple never used it. Atari never used it. And the only Amiga that used it only did so after Commodore had gone bankrupt and been acquired by another company. There have also been some processor upgrades built around the 68060.

The 68060 is the highest performing member of the Motorola 680×0 family of CPUs. It runs at twice the internal clock speed of the 68040 at the same bus speed, has separate 8 KB data and instruction caches (twice as big as in the 68040), and provides 3.0-3.5 times the power of the 68040. It can be used to replace the 68040 CPU using a software patch provided by Motorola, and it can run in 100% 68040 compatible mode.

The 68060 was introduced in 1994. It was initially available at 50 MHz, and later versions ran at 66 MHz and 75 MHz. There is also a 68LC060 version that lacks a floating point unit, much like the 68LC040 used in some Macintosh Centris and PowerBook computers.

The 68060 was used in the 1995 version of the Amiga 4000T, where it ran at 50 MHz.

There was no 68050 CPU, and Motorola switched its attention to PowerPC after the 68060.

DayStar Turbo 060, the Upgrade That Never Shipped

DayStar announced a line of Turbo 060 processor upgrades in the May 1994 issue of Macworld. DayStar’s plan was to produce versions for the 68030 PDS (Processor Direct Slot) and 68040 PDS, allowing several Mac II models and many Quadras to graduate to 68060 power. The top-end Turbo 060 would have a 66 MHz CPU and four onboard memory slots for 72-pin SIMMs, eliminating the need to access slower memory on the Mac’s logic board. A low-end version would run at 50 MHz.

Rumor has it that Apple put the kibosh on the Turbo 060, because its performance let old, discontinued Macs rival the performance of Apple’s new Power Mac line, built around the PowerPC 601 CPU at 60-80 MHz. Apple apparently saw the Turbo 060 as a threat to its PowerPC plans, so it didn’t allow DayStar to license the Mac ROMs necessary for the 68060 upgrade to run. (According to a former DayStar employee, the Turbo 060 wasn’t any faster than a 68040 at the same clock speed, so the big benefit would be from the higher clock speed, moving from a 20-33 MHz+ 68040 to a 50-66 MHz 68060, which would still double processing power for many users.)

+ Apple only used the 40 MHz 68040 in the Quadra 840av, and neither of the AV Macs had processor direct slots, so upgrading those machines to 68060 wasn’t an option.

At the same time it was working on the Turbo 060, DayStar was designing PowerPC 601-based upgrades for the 68030 PDS, 68040 PDS, and some 68040 Macs that used the LC PDS.

On the Amiga

In addition to the Amiga 4000T being designed around the 68060, there was also some 68060 upgrades for the Amiga 1200T, including the 50 MHz upgrade from Blizzard and the 50 MHz CyberStorm MK-II. Some enterprising individuals also made adapters that let a 68060 function in a 68040 socket, but these ran at the clock speed of the original CPU.

On the Atari ST

The CT60 and CT63 are 68060 upgrades for the Atari Falcon. The upgrade was designed to function at 80-100 MHz, with 90-95 MHz being typical. A few users managed to clock the CT63 to 106 MHz.

As an upgrade from the 16 MHz 68030 CPU in the Falcon, this was an impressive upgrade in pure processing power!

Motorola 680×0 Family Overview

CPU       speed*      L1 cache     FPU**    notes
68000     8-16 MHz          none      none  16-bit data bus, 24-bit addressing
68020       16 MHz     256 bytes     68881
68030    16-40 MHz   2x256 bytes     68882  internal PMMU, supports L2 cache
68LC040  20-25 MHz  2x4096 bytes      none  can be replaced with 68040
68040    25-40 MHz  2x4096 bytes  internal
68060    50-75 MHz  2x8192 bytes  internal
__________
* as used in Apple computers
** FPU typically used with this CPU

Motorola CPUs: 68000, 68020, 68030, 68040, 68060

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