| OCR Text |
Show 38 communication traffic. A processor may send the maximum PP to its neighbors when the communication channel is full or nearly full to avoid further influx of tasks. This type of PP packet obviously needs special treatment to bypass all preceding queued messages, either application or system packets. Furthermore, implementing a dedicated PP channel is inexpensive. Since the interval of updating is not very critical, the load balancing controller can communicate with a bit-serial, asynchronous channel. The speed of the channel may depend on the technology. The physical interconnect for the load balanc-ing purpose only consists of four wires per neighboring pair. A sketch of a load balanctng controller is shown in Figure 8. The load manager receives one asynchronous serial signal from each neighbor and assembles the serial bits into a byte. This byte value represents the current PP of a neighbor. These PPs are compared to find the minimum. The information of minimum PP neighbor and the saturation state of the system is passed to the communication switch for load migration. The. local loading condition is input from the attached processor through processor status lines shown at the right side of Figure 8. The controller computes the appropriate current PP based on the gradient algorithm and transmits it to all neighbors. Several additional signals are included for reliability purposes. The processor fail signal is activated when the local processor fails the selfdiagnosis, or other diagnostic measure. This signal forces the load controller to broadcast maximum PP to neighbors and disable all load balancing channels. The proces.sor can also selectively disable one or more neighbors by activating corresponding disable signals. · · As shown in Figure 8, a 20 pin dual-in-line load balancing controller chip can accommodate up to four interconnect channels. The controller may handle .. even more channels if an appropriate encoding technique is used. Since all load balancing channels run at the same communication speed, the controller needs only one baud rate generator to sample the asynchronous data. The sp·eed can handle 9600 bits per second without difficulty. At this speed, the |
