Sperry said its PC microIT will out-power the IBM PC XT model 286 introduced Tuesday, for a similar price. Also, Compaq priced its new Deskpro 286 in the same range. All three machines are based on the Intel 80286 microprocessor. Digital Equipment Corp. is scheduled to unveil a new personal computer today. However, Compaq is expected to introduce a completely new model, based on the next-generation chip, the Intel 80386.