MacLife - USA (2020-09)

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ONE OF THE advantages of

the Macintosh, from its launch

in 1984, was the Motorola

68000 processor, which was

inherently more powerful than

the IBM PC’s Intel 8088. But

by the late 1980s the 68000

series was falling behind CEO

John Sculley’s ambitions for

the high–end market, and

a Cray supercomputer was

wheeled in to enable the

in–house development of

a brand new CPU.

The effort, codenamed

Aquarius, fizzled out when

it emerged that designing

silicon was a very different

enterprise to building

computers. Its successor,

Jaguar, focused on the

upcoming Motorola 88110

— a new chip based on RISC

technology, departing from

the CISC architecture of the

68000 and 8088. The catch

was that switching the Mac

to RISC would mean rewriting

its operating system from

scratch. The prototype was

a Unix–based OS called Mach,

originally developed at

Carnegie Mellon University in

Pittsburgh by Avie Tevanian.

Tevanian had since been hired

by Steve Jobs’ NeXT, which

was working on developing

similar hardware ideas.

Meanwhile, engineer Jack

McHenry started a rival

backroom project, codenamed

Cognac after RISC expert

John Hennessy (today the

chair of Google’s parent

company, Alphabet). Its

strategy was to develop

68000 emulation software

that could quickly be adapted

to any RISC chip. When plans

for a new RISC series emerged

in 1991 from a skunkworks

collaboration between Apple

and IBM, it took just a year for

the PowerPC 601 processor to

arrive at Apple. But Jaguar,

now known as Tesseract,

showed no signs of being

ready to run on it.

Cognac — renamed PDM

after the Piltdown Man, an

evolutionary “missing link”

— ran existing 68000 Mac

apps seamlessly on PowerPC.

Its adoption enabled the first

Power Macintosh models to

be launched in March 1994

running an only mildly

customized version of the

System 7 OS. The impossible

had been made simple.

NEXT ISSUE ON SALE

SEP 15

RANDOM APPLE MEMORY

PowerPC

transition

Apple’s first processor switch was

fraught behind the scenes but

flawless up front, recalls

Adam Banks

The Power Macintosh was

a significant development

in Apple’s vision.

RAM

86 SEP 2020 maclife.com