A NEW notebook computer range, that Apple plans to release within two months, will use PowerPC processors designed by its alliance with IBM and Motorola, according to sources. Apple, however, is unwilling to release details of the range, and a spokesman said only: ''We are looking at a new chip and we are looking at brand new designs. So, we're looking at basically extending the current Powerbook [notebook] range to a brand new design.'' The Apple-Motorola-IBM alliance shook the industry recently with its new PowerPC chip. The alliance aims to use the PowerPC to shake the dominance of Intel, whose processors are found in most of the world's PCs. It asserts that the PowerPC is three times faster and less than half the cost of Intel's fifth-generation Pentium chip. The Power chips use a Reduced-Instruction-Set Computing (RISC) standard, which means they work faster than Intel's Complex-Instruction-Set Computing (CISC) chips. The spokesman said the new line would involve more than changing the central processor. ''There will definitely be a lot of changes. So, it's going to be a brand new generation of products,'' she said. Faster processors, incompatible software and more efficient power management have been threatening to leave Apple's Powerbook notebook behind. There were plans to allow customers an option to upgrade the notebooks to PowerPC, she said.