Apple also said the operating system would have the ability to do several computations at once, one of the strengths of IBM's PS/2 line of personal computers.

One reason for the slide: IBM's OS/2 operating system, which controls the basic functions of the PS/2, requires a large amount of memory, which is expensive. Last week, IBM announced rebates of up to $800 on memory packages to entice new customers.

Analysts say rising PS/2 sales would cut into Compaq's market share, which already dropped one point last week after IBM introduced its price rebates and two upgraded machines.