Abstract: An integrated circuit (203) for use in processing streams of data generally and streams of packets in particular. The integrated circuit (203) includes a number of packet processors (307, 313, 303), a table look up engine (301), a queue management engine (305) and a buffer management engine (315). The packet processors (307, 313, 303) include a receive processor (421), a transmit processor (427) and a risc core processor (401), all of which are programmable. The receive processor (421) and the core processor (401) cooperate to receive and route packets being received and the core processor (401) and the transmit processor (427) cooperate to transmit packets. Routing is done by using information from the table look up engine (301) to determine a queue (215) in the queue management engine (305) which is to receive a descriptor (217) describing the received packet's payload.

Abstract: An integrated circuit (203) for use in processing streams of data generally and streams of packets in particular. The integrated circuit (203) includes a number of packet processors (307, 313, 303), a table look up engine (301), a queue management engine (305) and a buffer management engine (315). The packet processors (307, 313, 303) include a receive processor (421), a transmit processor (427) and a risc core processor (401), all of which are programmable. The receive processor (421) and the core processor (401) cooperate to receive and route packets being received and the core processor (401) and the transmit processor (427) cooperate to transmit packets. Routing is done by using information from the table look up engine (301) to determine a queue (215) in the queue management engine (305) which is to receive a descriptor (217) describing the received packet's payload.

Abstract: A method of compacting an instruction queue in an out of order processor includes determining the number of invalid instructions below and including each row in the queue, by counting invalid bits or validity indicators associated with rows below and up to the current row. For each row, multiplexor select signals are generated from the flat vector counts for the N rows above and including the present row, and from the validity indicators associated with the N rows, where N is a predetermined value. A multiplexor associated with a particular row selects one of the N rows according to the select value, and moves or passes the instruction held in the selected row to the present row. A row's select value is determined by forming a diagonal from the N count vectors corresponding to the N rows above and including the present row, and logically ANDing, each diagonal bit with the valid bit associated with the same row. Each row's count vector is determined in two stages.

Abstract: A method of compacting an instruction queue in an out of order processor includes determining the number of invalid instructions below and including each row in the queue, by counting invalid bits or validity indicators associated with rows below and up to the current row. For each row, multiplexor select signals are generated from the flat vector counts for the N rows above and including the present row, and from the validity indicators associated with the N rows, where N is a predetermined value. A multiplexor associated with a particular row selects one of the N rows according to the select value, and moves or passes the instruction held in the selected row to the present row. A row's select value is determined by forming a diagonal from the N count vectors corresponding to the N rows above and including the present row, and logically ANDing, each diagonal bit with the valid bit associated with the same row. Each row's count vector is determined in two stages.

Abstract: An arbiter system for the instruction issue logic of a CPU has at least two encoder circuits that select instructions in an instruction queue for issue to first and second execution units, respectively, based upon the positions of the instructions within the queue and requests by the instructions for the first and/or second execution units. As a result, since the instruction can request different execution units, this system is compatible with architectures where the execution units may have different capabilities to execute different instructions, i.e., each integer execution unit may not be able to execute all of the instructions in the CPU's integer instruction set. According to the present invention, one of the encoder circuits is subordinate to the other circuit. The subordinate encoder circuit selects instructions from the instruction queue based not only on the positions of the instructions and their requests, but the instruction selection of the dominant encoder circuit.

Abstract: Instruction issue logic is disclosed that assesses register availability. The issue logic comprises register scoreboard logic that includes destination register storage elements to identify destination registers of instructions queued for issue. An arbiter selects instructions for issue during a machine cycle from the queued instructions. Register-clean wires associated with each register are driven in response to the corresponding destination storage elements and the arbiter. These wires are used to identify the read-availability of registers. Specifically, such a logic system is capable of reflecting freed registers on the subsequent machine cycle so that previously issued instructions do not hinder queuing of new instructions, unless they require multiple cycles to complete. To increase speed of operation, single NMOS devices bridge the register-clean wires and the issue signal from the arbiter.

Abstract: A set associative cache using decoded data element select lines which can be selectively configured to provide different data sets arrangements. The cache includes a tag array, a number of tag comparators corresponding to the maximum possible number of sets, a data element select logic circuit, and a data array. The tag and data arrays each provide, in response to an input address, a number of output tag and data elements, respectively. The number of output tag and data elements depends upon the maximum set size desired for the cache. An input main memory address is used to address both the tag and data arrays. The tag comparators compare a tag field portion of the input main memory address to each element output from the tag array. The select logic then uses the outputs of the tag comparators and one or more of the input main memory address bits to generate decoded data array enable signals. The decoded enable signals are then coupled to enable the desired one of the enabled data elements.