(from an electronic Apple memo)
Apple's decision to call its PowerPC-based Macintosh models "Power Macintosh" computers, with numeric model designations, calls for an explanation of the model numbers as well as the name. To recap the 3/14 intro, here is our lineup of both regular and AV versions:
So what do the numbers mean? The first digit tells the form factor: 6000 is the thin "pizza-box" form as in the Quadra 610; 7000, the taller "deep-dish pizza" form as in the Quadra 650 (but the number derives from the Quadra 700); and 8000, the mini-tower form as in the 840.
Other designations will be: 9000, for a larger tower form as in the Quadra 950; 5000, for all-in-one machines; 3000 and 4000, for smaller, LC form factors; 1000, for PowerBooks; and 2000, for PowerBook Duos.
The second digit indicates the PowerPC chip inside: 100, for the 601; 300, for the 603; and 400, for the 604. For the 620 chip, 500 may be used. The third and fourth digits will be reserved for later models.
Finally, the digits following the slash indicate the chip's clock speed. The clock speeds were included after much discussion as a way of allowing speed-bumps without requiring a new model number. If the speed goes up, then we change only that part of the model number.