 CLP in general is a nonpreemptive, event-driven processor accessible in IBM NPU Assembler. Each CLP can execute up to two threads. IBM NPU Assembler language predictably con- tains integer operators, built-in functions, string operators, and string expressions. IBM has also devel- oped a native C compiler. Before that, the implication of the lack of high-level language support was that the architectural incompatibility between the NP4GS3 and the lower members of IBM's NP fam- ily-the e405-meant that assembly code for one cannot be used for the other. This could be a prob- lem for some users. It has been resolved with the arrival of IBM's NPU C compiler. To briefly address the computing model, NP4GS3 consists of four types of what IBM calls data handlers. Picocode executes when threads are dispatched using the appropriate handlers inside the CLP engine. Thirty-two handlers are available (the same as the number of threads): General Table Handler (GTH) A GTH handles control frames, which require access to tree mem- ory. There is only one GTH per NPU chip, and it operates only on the egress side of the network processor. Guided Frame Handler (GFH) The GFH handles control frames that are coming from or going to the CP or other NPU chips. A GFH can forward frames to the GTH by re-enqueueing frames to Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. IBM POWERNP™ IBN POWERNPTM the internal GTH queue. There is only one GFH per NPU, and it operates on either the ingress or the egress side of the network processor. General PowerPC Handler (GPH) The GPH handles control and data frames transmitted to or received from the CP processor. One thread receives flows and the other one transmits them. Each NP4GS3 network processor has two GPH. General Data Handler (GDH) The GDH handles data frames that enter from the network through the PHY ports. Each NP4GS3 ne