The Apple, IBM, Motorola alliance (AIM) is under stress due to disagreements over the PowerPC G4 chip, according to industry insiders.

IBM, insiders say has figured out a method for producing 500MHz G4 microprocessors in volume. Motorola, it seems, has not yet found a way around certain manufacturing problems.

IBM chose to manufacture G4 processors for Apple just before Christmas, 1999. Today, IBM is able to yield more high-speed G4 chips per production run than Motorola, according to sources close to both companies.

The Register reports that Motorola is rumoured to be using: "Clauses in its AltiVec licensing deal with IBM to limit IBM's ability to sell to Apple."

IBM effectively left the Mac market to Motorola in early 1999, when it quit Somerset, the IBM/Motorola joint design centre. IBMs lack of enthusiasm called into question the future of the AIM alliance.

On IBMs decision to return, the Microprocessor Report said: "IBM gets to sell G4s to Apple, having invested little effort in developing the part. Motorola, presumably, gets royalties from the parts IBM sells."