When introduced, the original 68000 ran at only 8MHz. Subsequent 68000 chips operated at 16MHz with 24-bit data buses. The 68010 was about 15% faster than the original model at around 12MHz. Today, few 68010s are still being sold because they're fairly out-of-date.

The 68020 was the first model in the Motorola microprocessor family with a 32-bit external bus, and thus higher performance. Today the 68020 runs at 33MHz and has a 256-byte cache. The 68030, which also has a 32-bit bus, runs at up to 50MHz and has a 4KB cache. The 68040 is available at up to 40MHz and has a 4KB cache. There is no 68050 in the series.

The newest microprocessor in the High Performance series is the 68060, which is just beginning to ship. The 68060 runs at up to 60MHz, has an 8KB cache, and incorporates superscalar technology, which enables systems to start multiple instructions during one clock cycle to speed up processing. The performance of the 68060 is comparable to the performance of the PowerPC 601 and 603 microprocessors.

Beginning with the 68030, all the microprocessors in the series have incorporated on-chip memory management units. The 68040 and 68060 have floating-point processing, allowing the microprocessor to work with floating-point numbers and other mathematical equations more easily. (Floating-point numbers represent numbers ending in many zeros.)

Initially, the 68000 microprocessors were used heavily in engineering workstations. Then in the mid-1980s, Apple Computer Inc. adopted the 68000 microprocessor architecture, and it basically became the "heart and soul" of the Macintosh product line, says Roy Druian, marketing manager at Motorola. Today Apple continues to ship Macintosh machines that are based on 68000-series microprocessors.

The 68000 series of microprocessors used in desktop systems is primarily based on the Apple product line. Apple recently introduced a series of desktop computers known as the Performa 600 series, which is based on the 68040. The Apple Powerbook 500 series of notebook computers is also based on the 68040. The prior Powerbook series was 68030-based. There are even some 68030-based Performas that are still shipping. But overall, Druian says, Apple is phasing out its 68030 product line with the 68040 line, and probably won't announce any desktop products based on the 68060.

"Essentially," Druian says, "this current series of Macintosh products that's based specifically on 68040s is sort of going to be the end of [68000-series] support [in desktop systems]."

Though the 68000 series has been the core of desktop Macintosh computers for some time, this family of microprocessors has shifted away from the desktop-computer market into what's commonly referred to as the embedded-systems marketplace. Embedded systems include things like laser printers, modems, telecommunications products, and other such devices that utilize microprocessor chips, but are not desktop computers or network servers.

Druian says many 68020s are shipping today in items such as laser printers and copy machines. You're not aware that there's a 68020 microprocessor in the machine, but there are plenty of them still on the market.

Just because the 68000 series is moving completely into embedded systems doesn't mean Motorola will be out of the desktop-computer market. That's where the PowerPC comes in. Apple has made it known that it's moving its desktop product line to the PowerPC. The migration from 68030s and 68040s to the PowerPC will be gradual. You'll still see some Macintosh desktop computers with 68000-series microprocessors in them for awhile. To aid the migration process, however, Apple is selling PowerPC upgrades for many of its 68000-based products.

Since Motorola has a part in the PowerPC, it has room to go elsewhere with the 68000 High Performance series.

"It's not really our focus to serve the desktop market with [the 68000] family," Druian says. "Our real focus is to establish the PowerPC into that desktop range." The 68000 family is more geared toward serving the users of embedded systems.

by Jennifer Larson