Abstract: A computer system (8) comprising a central processing unit (12) and a memory hierarchy. The memory hierarchy comprises a first cache memory (16) and a second cache memory (26). The first cache memory is operable to store non-pixel-information, wherein the non-pixel information is accessible for processing by the central processing unit. The second cache memory is higher in the memory hierarchy than the first cache memory, and has a number of storage locations operable to store non-pixel information (26b) and pixel data (26a). Lastly, the computer system comprises cache control circuitry (24) for dynamically apportioning the number of storage locations such that a first group of the storage locations are for storing non-pixel information and such that a second group of the storage locations are for storing pixel data.

Abstract: This invention is memory system including plural memory banks logically disposed into an array of X rows and Y columns. A first decoder selectively powers one of the Y columns corresponding to a first predetermined set of address bits. A second decoder selectively powers one of the X rows corresponding to a second predetermined set of address bits. Multiplexers select the powered memory bank for data access. Thus one of the plural memory banks is powered and selected for memory access corresponding to the first and second predetermined sets of bits of the received address. This memory system is preferably a cache memory including a further column of memory banks for cache addresses and cache control data including at least a cache valid tag. A multiplexer selects one row corresponding to the second predetermined set of address bits.

Abstract: The present invention is a code preparation system (12) which accepts input code (11) in intermediate code format, our source code format which is first translated into intermediate format, analyzes the intermediate code, then provides optimization information, hints, and/or directions (collectively referred to as “optimization information”) for optimizing execution of the intermediate code by a code interpretive runtime environment, such as a Java Virtual Machine. The code interpretive runtime environment is operable to selectively implement the optimization information received from the code preparation system (12). The optimization information is provided to the code interpretive runtime environment in the form of additional attributes added to a class file (14) generated by the code preparation system (12).

Abstract: A data processing circuit has an adder unit divided into plural sections. Each section receives a subset of the bits of the operands and generates a subset of the bits of the resultant. A carry multiplexer is disposed between the sections. This carry multiplexer selects one of a plurality of possible carry inputs to the following sections. The data processing circuit may make the specification of the selection of the carry control multiplexers by: the opcode of the instruction; a combination of the opcode and an opcode modification field; an immediate field directly specifying carry control signals; or designation a carry control register which stores the carry control signals. The adder unit may be divided into sections of equal size or of unequal size.

Abstract: In a computer system (10) embodiment, there is included a memory (18) and circuitry (16a) for prefetching information from the memory in response to a prefetch request. The system further includes a system resource (14), wherein the system resource is burdened in response to a prefetch operation by the circuitry for prefetching information. The system resource is also further burdened in response to other circuitry (16b, 16n, 17) using the system resource. The system further includes circuitry (20, 22, 24) for determining a measure of the burden on the system resource. Lastly, the system includes circuitry (26) for prohibiting prefetching of the information by the circuitry for prefetching information responsive to a comparison of the measure of the burden with a threshold. Other circuits, systems, and methods are also disclosed and claimed.

Abstract: A multiple cycle memory access unit issues a memory access load or store, delaying a predetermined number of instruction cycles between it activation and its initial data transfer. The multiple cycle memory access unit controls a predetermined plural number of accesses and operates independently and in parallel with the instruction flow of the data processor. The multiple cycle memory access unit delays a predetermined number of instruction cycles between sequential data transfers of the predetermined number of data transfers. This predetermined period may be the same as the initial delay or it may be determined independent of the initial delay. The operation of the multiple cycle memory access unit is subject to predication on an instruction specified data registers. The multiple cycle memory access unit preferably provides predetermined register number cycling among the plural data registers.

Abstract: This invention is a very long instruction word data processor including plural data registers, plural functional units and plural program counters and is selectively operable in either a first or second mode. In the first mode, the data processor executes a single instruction stream. In the second mode, the data processor executes two independent program instruction streams simultaneously. In the second mode the data processor may respond to two instruction streams accessing only corresponding halves of the data registers and function units. Alternatively, the data processor may respond to a first instruction stream including instructions referencing the whole data processor employing A side function units by alternatively dispatching (1) instructions referencing the A side data registers and the A side function units and (2) instructions referencing the B side data registers and the B side function units. In the first mode, the data processor fetches N bits of instructions each cycle.

Abstract: A microprocessor (12) comprising a memory system (20) for outputting data in response to an address, wherein the memory system is further operable to receive a prefetch request having a predicted target data address. The microprocessor further includes a load target circuit (56 or 112), which comprises a first plurality of entries (116) of a first length and a second plurality of entries (114) of a second length. Each of the first plurality of entries comprises a value (ADDRESS TAG) for corresponding the entry to a corresponding first plurality of data fetching instructions. Further, each of the first plurality of entries further comprises a value (POINTER A) for indicating a corresponding predicted target data address. Each of the second plurality of entries also comprises a value (ADDRESS TAG) for corresponding each of the second plurality of entries to a corresponding second plurality of data fetching instructions.

Abstract: In one embodiment, there is a single integrated circuit microprocessor (10). The microprocessor has an instruction pipeline (12) which comprises an execution stage (12a) operable to process an information unit of a first length. The microprocessor further includes a cache circuit (20) comprising a memory (34) operable to store a transfer unit of information of a second length and accessible by the instruction pipeline. The second length corresponding to the capability of the cache circuit is greater than the first length corresponding to the execution stage operability. Lastly, the microprocessor includes a block move circuit (24) coupled to the cache circuit and operable to read/write a transfer unit of information of the first length into the memory of the cache circuit.

Abstract: A programmable logic device, such as a digital signal processor (DSP) (130), having a Chien search unit (116) is disclosed. The Chien search unit (116) is arranged to perform finite field arithmetic functions useful in identifying roots of a polynomial, as is useful in Reed-Solomon decoding, particularly, after the execution of a Euclidean array function. Galois field multipliers (306) perform finite field multiplication of coefficient values (&Lgr;) and powers of symbol values (&agr;); the products of such multiplications are written into the coefficient register (304) for use in connection with the next symbol value. Finite field adders (308, 310; 318, 320) produce a final sum that is interrogated by zero detection circuitry (206) to determine whether a root is presented by the current symbol value.

Abstract: A microprocessor (12) comprising a cache circuit (20) and circuitry (46, 48, 41, 56) for issuing a prefetch request. The prefetch request (82) comprises an address (82a) and requests information of a first size (82b) from the cache circuit. The microprocessor also includes prefetch control circuitry (22), which comprises circuitry for receiving the prefetch request and evaluation circuitry for evaluating system parameters corresponding to the prefetch request. Additionally, the prefetch control circuitry comprises circuitry, responsive to the evaluation circuitry, for determining a size of information for a prefetch operation starting at the address from the cache circuit, where the prefetch operation corresponds to the prefetch request.

Abstract: A microprocessor (5) for coupling to an external read/write memory (20) having an addressable storage space. This storage space stores cacheable digital data and non-cacheable (32) digital data. The microprocessor includes a data storage circuit (62) for storing a portion of the non-cacheable data. The microprocessor further includes an address storage circuit (64) for storing an address corresponding to the portion of the non-cacheable data. Still further, the microprocessor includes a counter (72) for advancing a count from an initial value (74) toward a threshold value (76) in response to an activity over time. The counter initiates its advancing operation in response to the data storage circuit receiving the portion of the non-cacheable data. Lastly, the microprocessor includes an indicator (66) for indicating the portion of the non-cacheable data in the data storage circuit is expired in response to the count reaching a threshold.

Abstract: A microprocessor (62) for coupling to an external read/write memory (70) having an addressable storage space for storing data. The microprocessor includes a data storage circuit (76) for storing a portion of the data, where that portion of data comprises non-cacheable data. The microprocessor further includes a class storage circuit (80) for storing a class identifier corresponding to the portion of the non-cacheable data, as well as an input (TERMINATE) for receiving a terminate signal and an input (CLASS) for receiving a class signal. Lastly, the microprocessor includes an indicator (82) for indicating that the portion of the non-cacheable data in the data storage circuit is expired in response to assertions of the terminate signal and the class signal matching the class identifier.

Abstract: In a computer system (10) embodiment, there is included a memory (18) and circuitry (16a) for prefetching information from the memory in response to a prefetch request. The system further includes a system resource (14), wherein the system resource is burdened in response to a prefetch operation by the circuitry for prefetching information. The system resource is also further burdened in response to other circuitry (16b, 16n, 17) using the system resource. The system further includes circuitry (20, 22, 24) for determining a measure of the burden on the system resource. Lastly, the system includes circuitry (26) for prohibiting prefetching of the information by the circuitry for prefetching information responsive to a comparison of the measure of the burden with a threshold. Other circuits, systems, and methods are also disclosed and claimed.

Abstract: A microprocessor with an execution stage (26) including a plurality of execution units and an instruction memory (32) for storing instructions. The microprocessor further includes circuitry for retrieving (14) instructions from the instruction memory. This retrieving circuitry may retrieve one instruction simultaneously with the execution of another instruction by one of the plurality of execution units. Further, this retrieving circuitry includes a branch target memory (30) for storing a plurality of information fields (30r) corresponding to a branch instruction. The information fields include at least a target instruction address (Tn), a prediction field (Pn) indicating whether or not program flow should pass to the target instruction address, and an accuracy measure (PPAn) indicating accuracy for past prediction fields.

Abstract: A microprocessor operates at a rate dependent upon the interrupt source of a plurality of interrupt sources. The rate of power consumption by the microprocessor corresponds to the selected rate of instruction operation. A rate table accessed upon receipt of an interrupt stores a table of interrupt source to rate of instruction operation. The rate table may be a read only memory or a read/write memory loaded upon initiation of the microprocessor. The rate of microprocessor instruction operation may be set by frequency of an instruction clock or by a rate of instruction dispatch. For a superscalar microprocessor the rate of instruction operation may be set by setting a number of instructions dispatched per instruction cycle. On receiving an interrupt a rate number is pushed onto a rate stack. On return from the interrupt the rate stack is popped. The microprocessor operates at a rate corresponding to the rate number at a top of the rate stack.

Abstract: A microprocessor preemptively write-backs dirty entries of an internal cache. Each cache entry is checked once each predetermined time period to determine if the cache entry is dirty. If dirty, a write history is checked to determine if the cache entry is stale. If stale, the cache entry in preemptively written back to main memory and then marked as clean. The write history includes a count of the number of consecutive predetermined time periods during which there is no write to the cache entry. The cache entry is stale if the count exceeds a predetermined number. For each check of the write history the nonwrite count is incremented if the cache entry has been written to during the prior cycle and decremented if not. Alternatively, the nonwrite count is set to zero if the cache entry has been written to. The dirty cache entry may be marked as clean upon copying to the write-back buffer or, alternatively, when the write-back buffer writes the dirty cache entry to the main memory.

Abstract: A microprocessor (10) and corresponding system (300) is disclosed in which prefetch of instruction or data from higher level memory (11; 307; 305) may be performed in combination with a fetch from a lower level cache (16). A branch target buffer (56) has a plurality of entries (63) associated with branching instructions; in addition to the tag field (TAG) and target field (TARGET), each entry (63) includes prefetch fields (PF0 ADDR; PF1 ADDR) containing the addresses of memory prefetches that are to be performed in combination with the fetch of the branch target address. Graduation queue and tag check circuitry (27) is provided to update the contents of the prefetch fields (PF0 ADDR; PF1 ADDR) by interrogating instructions that are executed following the associated branching instruction to detect instructions that involve cache misses, in particular the target of the next later branching instruction.

Abstract: A microprocessor (10) and a system (300) incorporating the same is disclosed, in which branch prediction is effected in response to the type of program in which branching instructions are contained. A fetch unit (26) includes a branch target buffer (56) and a plurality of pattern history tables (53). Select logic (80) receives signals indicating, for each branching instruction, the type of program containing the instruction, and selects one of the pattern history tables (53) for use in generating a prediction code in response to a portion of a branch history field (BH) in an entry (63) of the branch target buffer (56) corresponding to the instruction address. Disclosed examples of the signals used in selecting the pattern history table (53) include an indication (U/S) of the privilege level (e.g., user-level or supervisor-level) of the instruction.

Abstract: A host module (2) including a host CPU (10) and a configurable expansion bus controller (28, 28', 128) is disclosed. The expansion bus controller (28, 28', 128) is configurable by way of configuration signals (BCFG) to be operable in various bus configurations for communicating signals between a module bus (IBUS) and external buses (XPCI1, XPCI0). These modes include combining the external buses (XPCI1, XPCI0) into a single bus of the 64-bit PCI type, operating the external buses (XPCI1, XPCI0) as separate 32-bit PCI buses, as separate CardBus buses, as separate AGP buses (either at one or multiple data transfers per cycle), or as combinations thereof. Certain of the configuration signals (BCFG) are used to select the clock frequencies at which the external buses (XPCI1, XPCI0) operate, in either of the 64-bit or 32-bit PCI protocols, or in the AGP bus protocol when present.