Abstract: A processor including a first execution core section clocked to perform execution operations at a first clock frequency, and a second execution core section clocked to perform execution operations at a second clock frequency which is different than the first clock frequency. The second execution core section runs faster and includes a data cache and critical ALU functions, while the first execution core section includes latency-tolerant functions such as instruction fetch and decode units and non-critical ALU functions. The processor may further include an I/O ring which may be still slower than the first execution core section. Optionally, the first execution core section may include a third execution core section whose clock rate is between that of the first and second execution core sections. Clock multipliers/dividers may be used between the various sections to derive their clocks from a single source, such as the I/O clock.

Abstract: A processor including a first execution core section clocked to perform execution operations at a first clock frequency, and a second execution core section clocked to perform execution operations at a second clock frequency which is different than the first clock frequency. The second execution core section runs faster and includes a data cache and critical ALU functions, while the first execution core section includes latency-tolerant functions such as instruction fetch and decode units and non-critical ALU functions. The processor may further include an I/O ring which may be still slower than the first execution core section optionally, the first execution core section may include a third execution core section whose clock rate is between that of the first and second execution core sections. Clock multipliers/dividers may be used between the various sections to derive their clocks from a single source, such as the I/O clock.

Abstract: A method and apparatus are disclosed for staggering execution of an instruction. According to one embodiment of the invention, a single macro instruction is received wherein the single macro instruction specifies at least two logical registers and wherein the two logical registers respectively store a first and second packed data operands having corresponding data elements. An operation specified by the single macro instruction is then performed independently on a first and second plurality of the corresponding data elements from said first and second packed data operands at different times using the same circuit to independently generate a first and second plurality of resulting data elements. The first and second plurality of resulting data elements are stored in a single logical register as a third packed data operand.

Abstract: A processor including a first execution core section clocked to perform execution operations at a first clock frequency, and a second execution core section clocked to perform execution operations at a second clock frequency which is different than the first clock frequency. The second execution core section runs faster and includes a data cache and critical ALU functions, while the first execution core section includes latency-tolerant functions such as instruction fetch and decode units and non-critical ALU functions. The processor may further include an I/O ring which may be still slower than the first execution core section. Optionally, the first execution core section may include a third execution core section whose clock rate is between that of the first and second execution core sections. Clock multipliers/dividers may be used between the various sections to derive their clocks from a single source, such as the I/O clock.

Abstract: The present invention discloses a method and apparatus for matching data types of operands in an instruction. A type code of an operand used by the instruction is determined. An attribute value of a storage element which corresponds to the operand is read from a speculative array. This attribute value is then compared with the type code.

Abstract: A cache memory is constituted with a data array and control logic. The data array includes a number of data lines, and the control logic operates to store a number of trace segments of instructions in the data lines, including trace segments that span multiple data lines. In one embodiment, each trace segment includes one or more trace segment members having one or more instructions, with each trace segment member occupying one data line, and the data lines of a multi-line trace segment being sequentially associated (logically). Retrieval of the trace segment members of a multi-line trace segment is accomplished by first locating the data line storing the first trace segment member of the trace segment, and then successively locating the remaining data lines storing the remaining trace segment members based on the data lines' logical sequential associations.

Abstract: A cache technique for maximizing cache efficiency by assigning ages to elements which access the cache, is described. In one embodiment, the cache technique includes receiving a first element of a first type by a cache and writing the first element in a set of the cache. The first element has a first age. The cache technique further includes receiving a second element of a second type by the cache and writing the second element in the set of the cache. The second element has a middle age, where the first age is a more recently used age than the middle age. In another embodiment, the cache technique includes receiving a first element of a first stream by a cache and writing the first element in a set of the cache. The first element has a first age. The cache technique further includes receiving a second element of a second stream by the cache and writing the second element in the set of the cache. The second element has a middle age, where the first age is a more recently used age than the middle age.

Abstract: Maximum throughput or "back-to-back" scheduling of dependent instructions in a pipelined processor is achieved by maximizing the efficiency in which the processor determines the availability of the source operands of a dependent instruction and provides those operands to an execution unit executing the dependent instruction. These two operations are implemented through number of mechanisms. One mechanism for determining the availability of source operands, and hence the readiness of a dependent instruction for dispatch to an available execution unit, relies on the prospective determination of the availability of a source operand before the operand itself is actually computed as a result of the execution of another instruction. Storage addresses of the source operands of an instruction are stored in a content addressable memory (CAM).

Abstract: A processor is disclosed comprising a front end circuit that fetches a series of instructions according to a program sequence determined by at least one branch prediction, a register renaming circuit that allocates execution resources to each instruction, and an execution circuit that executes each instruction in the instruction stream. The execution circuit causes the front end circuit to refetch the series of instructions if a branch misprediction is detected. A stall signal disables the register renaming circuit until the execution circuit commits the branch result to an architectural state according to the program sequence.

Abstract: A mechanism and method for renaming flags within a register alias table ("RAT") to increase processor parallelism and also providing and using flag masks associated with individual instructions. In order to reduce the amount of data dependencies between instructions that are concurrently processed, the flags used by these instructions are renamed. In general, a RAT unit provides register renaming to provide a larger physical register set than would ordinarily be available within a given macroarchitecture's logical register set (such as the Intel architecture or PowerPC or Alpha designs, for instance) to eliminate false data dependencies between instructions that reduce overall superscalar processing performance for the microprocessor. The renamed flag registers contain several flag bits and various flag bits may be updated or read by different instructions.

Abstract: A cache memory is constituted with a data array and control logic. The data array includes a number of data lines, and the control logic operates to store a number of trace segments of instructions in the data lines, including trace segments that span multiple data lines. In one embodiment, each trace segment includes one or more trace segment members having one or more instructions, with each trace segment member occupying one data line, and the data lines of a multi-line trace segment being sequentially associated (logically). Retrieval of the trace segment members of a multi-line trace segment is accomplished by first locating the data line storing the first trace segment member of the trace segment, and then successively locating the remaining data lines storing the remaining trace segment members based on the data lines' logical sequential associations.

Abstract: A method and circuitry for coordinating exceptions in a processor. The processor generates a result data value and an exception data value for each instruction wherein the exception data value specifies whether the corresponding instruction causes an exception. The processor commits the result data values to an architectural state of the processor in the sequential program order, and fetches an exception handler to processes the exception if the exception is indicated by one of the exception data values. The processor fetches an asynchronous event handler to processes an asynchronous event if the asynchronous event is detected while the result data values are committed to the architectural state of the processor.

Abstract: A mechanism for efficiently overlapping multiple operand types is used in a microprocessor which includes a plurality of execution units and a mechanism to provide operations, which include one or more operands, to the plurality of execution units. Each of the plurality of execution units interprets the one or more operands as different types of operands, and the mechanism to provide operations overlaps the different types of operands.

Abstract: A buffer is used to store information about the branch instructions within a pipelined microprocessor that can speculatively execute instructions. When a branch instruction in the microprocessor is decoded, the address of the instruction immediately following the branch instruction (the Next Linear Instruction Pointer or NLIP) and some processor state information is written into a Branch Instruction Pointer Table. The branch instruction then proceeds down the microprocessor pipeline. Eventually, the branch instruction is executed. The resolved branch outcome for the branch instruction is compared with a predicted branch outcome. If the branch prediction was correct, the microprocessor continues execution along the current path. However, if the branch prediction was wrong then the execution unit flushes the front-end microprocessor pipeline and restores the microprocessor state information that was stored in the Branch IP Table.

Abstract: This invention overcomes the address size backward compatibility problem by first subtracting the segment base address from the linear destination address of a branch instruction to generate a virtual destination address. It is assumed that the branch instruction destination address is n bits long with m most significant bits. It is desired to provide backward compatibility in the n-bit processor for branch instruction code written for processors utilizing instruction address fields of size (n-m) bits. After obtaining the virtual address, if any of the m most significant bits are non-zero, then those m bits are set to zero to thereby generate a corrected virtual address. If such a compatibility correction is necessary, then a clear signal is asserted to flush all state of the processor that resulted from instructions being fetched after the branch instruction was fetched. The corrected virtual address is added back to the segment base address to generate a corrected linear address.

Abstract: A Branch Target Buffer Circuit in a computer processor that predicts branch instructions with a stream of computer instructions is disclosed. The Branch Target Buffer Circuit uses a Branch Target Buffer Cache that stores branch information about previously executed branch instructions. The branch information stored in the Branch Target Buffer Cache is addressed by the last byte of each branch instruction. When an Instruction Fetch Unit in the computer processor fetches a block of instructions it sends the Branch Target Buffer Circuit an instruction pointer. Based on the instruction pointer, the Branch Target Buffer Circuit looks in the Branch Target Buffer Cache to see if any of the instructions in the block being fetched is a branch instruction. When the Branch Target Buffer Circuit finds an upcoming branch instruction in the Branch Target Buffer Cache, the Branch Target Buffer Circuit informs an Instruction Fetch Unit about the upcoming branch instruction.

Abstract: A method and apparatus for performing load operations in a computer system. The present invention includes a method and apparatus for dispatching the load operation to be executed. The present invention halts the execution of the load operation when a dependency exists between the load operation and another memory operation currently pending in the system. When the dependency no longer exists, the present invention redispatches the load operation so that it completes.

Abstract: Streaming buffer renaming for memory accesses issued by a microprocessor to an external memory via a system bus allows up to N fetch accesses at any one time for M physical streaming buffer locations, where N is greater than M. When a fetch within the processor misses the instruction cache, the fetch address is placed in the streaming buffer. When the data has been fetched from the external memory, it is returned to the streaming buffer and placed into one of the M physical buffer locations. The data within the streaming buffer is returned to the instruction cache of the processor only if it is to be used in accordance with the computer program being executed.

Abstract: A macro instruction is provided for a microprocessor which allows a programmer to specify a base value, index, scale factor and displacement value for calculating an effective address and returning that result in a single clock cycle. The macro instruction is converted into a micro operation which is provided to the single-cycle execution unit with the required source operands for performing the calculation. Within the single-cycle execution unit, the index and scale factor are provided to a left shifter for multiplying the two values. The result of the left shift operation is added to the sum of the base and displacement. This results in the effective address which is then returned from the single-cycle execution unit to a predetermined destination. This provides for the calculation of an effective address in a single cycle pipeline execution unit that is independent of the memory system execution units.

Abstract: A method and apparatus for executing a misaligned load. The method begins with receiving a load request to load data from a first memory location. An entry in a store buffer is tested to determine whether the entry corresponds to the first memory location. The entry is also tested to determine whether the entry corresponds to a second memory location subsequent to the first memory location. The load request is blocked if the entry corresponds to the first memory location or the second memory location. After a store operation for the store buffer entry is executed, the load request may be unblocked. The apparatus is a processor or a computer system comprising a load buffer capable of storing a load request address in response to a load request. The processor includes an incrementing circuit that generates an incremented load request address. The processor also includes a store buffer containing a portion of a store request address.