Business Notes COMPUTERS

It is fast -- four times as quick as the original. It is loud -- with stereo sound. It is expandable -- with six plug-in slots for peripheral devices. And for the first time on a Macintosh screen, it has color selected from a palette of 16 million hues and displayed on a 13-inch monitor. This week Apple Computer unveiled its Mac II, a spiffy unit priced at $3,899 (monitor not included). Yet the Mac II is most notable for a departure from Apple's previous products: with the proper accessories, it can run the huge library of software written for the IBM PC. Says Apple Chairman John Sculley, who bucked ten years of go-it-alone tradition to make Big Red compatible with Big Blue: "This is no longer a religious issue here."