A Z80-Style Microprocessor
A microprocessor is simply the main brains that tie together the memory devices, the keyboard, and other parts of the computer. You can also call it a central processing unit (CPU).
Okay, but why a Z80 in the Kaypro?
That’s simply a style of chip from a company called Zilog. “You could buy those all over the place,” Kay said. “We wanted something proven and reliable.” The Z80 was the only kind of CPU that could run CP/M (Control Program for Microcomputers)-style programs, then an industry standard.
The Z80, though, can’t handle programs as complicated as the newer 8088 chip that ended up in IBM PCs and countless clones. Here’s why.
A bit is a “1” or a “0.” Patterns of bits form bytes. And what’s a byte? Nothing more than a letter or number. So how does this tie in with the early Kaypro’s Z80 versus the IBM’s 8088?
Well, the Z80 processes information in words of only 8 bits at a time. The 8088 in the IBM, however, gulps it down in 16-bit chunks and works with larger memories—so that the IBM can run more complicated programs, like the more elaborate electronic spreadsheets for forecasting profit and loss. There’s another benefit, too. A 16-bitter doesn’t need to call up programming information as often from the spinning floppy disks, which are slower than the purely electronic memories.
The Kaypro II, however, won’t immediately become a has-bit—er, has-been. “Converting the Kaypro to a 16-bit machine is no big deal,” Kay observed. In fact, several months after he said it, his company announced a computer called the Kaypro II Plus 88 with both the 8-bit Z80 and the 16-bit 8088. It couldn’t run all IBM programs, especially those boasting graphics or pictures as well as words and numbers. Here, as in many cases, the term “IBM compatible” is grossly misleading. There are degrees of compatibility, and even if a computer supposedly uses the same style of floppy disks, you must test it with the program you want to run. (Many computer aficionados test for general IBM compatibility by running a game called Flight Simulator, or Lotus 1-2-3, a program combining a spreadsheet with graphics and several other capabilities.)
Some existing programs, by the way, are configured so that it doesn’t matter much whether you’re running the 8- or 16-bit version.
That will change as special programs come out for the 16-bit machines and as old ones, like WordStar, begin to take full advantage of 16-bit capabilities. Already Apple and other companies are writing new software for computers like the Macintosh, which, if not universally regarded as a true 32-bit machine, contains chips faster than the IBM’s 8088.
For many small businesses, however, 8 bits may be powerful enough even for number crunching as long as the right programs are available.
The wisdom in the micro business is that no machine is ever obsolete—just so it does the job for you.