Abstract: A method to eliminate the delay of a block invalidate operation in a multi CPU environment by overlapping the block invalidate operation with normal CPU accesses, thus making the delay transparent. A range check is performed on each CPU access while a block invalidate operation is in progress, and an access that maps to within the address range of the block invalidate operation will be treated as a cache miss to ensure that the requesting CPU will receive valid data.

Abstract: A method to eliminate the delay of a block invalidate operation in a multi CPU environment by overlapping the block invalidate operation with normal CPU accesses, thus making the delay transparent. A range check is performed on each CPU access while a block invalidate operation is in progress, and an access that maps to within the address range of the block invalidate operation is treated as a cache miss to ensure that the requesting CPU will receive valid data.

Abstract: A shared resource within a module may be accessed by a request from an external requester. An external transaction request may be received from an external requester outside the module for access to the shared resource that includes control information, not all of which is needed to access the shared resource. The external transaction request may be modified to form a modified request by removing a portion of the locally unneeded control information and storing the unneeded portion of control information as an entry in a bypass buffer. A reply received from the shared resource may be modified by appending the stored portion of control information from the entry in the bypass buffer before sending the modified reply to the external requester.

Abstract: This invention is a cache system with a memory attribute register having plural entries. Each entry stores a write-through or a write-back indication for a corresponding memory address range. On a write to cached data the cache the cache consults the memory attribute register for the corresponding address range. Writes to addresses in regions marked as write-through always update all levels of the memory hierarchy. Writes to addresses in regions marked as write-back update only the first cache level that can service the write. The memory attribute register is preferably a memory mapped control register writable by the central processing unit.

Abstract: The level one memory controller maintains a local copy of the cacheability bit of each memory attribute register. The level two memory controller is the initiator of all configuration read/write requests from the CPU. Whenever a configuration write is made to a memory attribute register, the level one memory controller updates its local copy of the memory attribute register.

Abstract: Speculative history forwarding in overriding branch predictors, and related circuits, methods, and computer-readable media are disclosed. In one embodiment, a branch prediction circuit including a first branch predictor and a second branch predictor is provided. The first branch predictor generates a first branch prediction for a conditional branch instruction, and the first branch prediction is stored in a first branch prediction history. The first branch prediction is also speculatively forwarded to a second branch prediction history. The second branch predictor subsequently generates a second branch prediction based on the second branch prediction history, including the speculatively forwarded first branch prediction. By enabling the second branch predictor to base its branch prediction on the speculatively forwarded first branch prediction, an accuracy of the second branch predictor may be improved.

Abstract: This invention optimizes DMA writes to directly addressable level two memory that is cached in level one and the line is valid and dirty. When the level two controller detects that a line is valid and dirty in level one, the level two memory need not update its copy of the data. Level one memory will replace the level two copy with a victim writeback at a future time. Thus the level two memory need not store write a copy. This limits the number of DMA writes to level two directly addressable memory and thus improves performance and minimizes dynamic power. This also frees the level two memory for other master/requestors.

Abstract: Management of access to shared resources within a system comprising a plurality of requesters and a plurality of target resources is provided. A separate arbitration point is associated with each target resource. An access priority value is assigned to each requester. An arbitration contest is performed for access to a first target resource by requests from two or more of the requesters using a first arbitration point associated with the first target resource to determine a winning requester. The request from the winning requester is forwarded to a second target resource. A second arbitration contest is performed for access to the second target resource by the forwarded request from the winning requester and requests from one or more of the plurality of requesters using a second arbitration point associated with the second target resource.

Abstract: This invention optimizes DMA writes to directly addressable level two memory that is cached in level one and the line is valid and dirty. When the level two controller detects that a line is valid and dirty in level one, the level two memory need not update its copy of the data. Level one memory will replace the level two copy with a victim writeback at a future time. Thus the level two memory need not store write a copy. This limits the number of DMA writes to level two directly addressable memory and thus improves performance and minimizes dynamic power. This also frees the level two memory for other master/requestors.

Abstract: This invention assures cache coherence in a multi-level cache system upon eviction of a higher level cache line. A victim buffer stored data on evicted lines. On a DMA access that may be cached in the higher level cache the lower level cache sends a snoop write. The address of this snoop write is compared with the victim buffer. On a hit in the victim buffer the write completes in the victim buffer. When the victim data passes to the next cache level it is written into a second victim buffer to be retired when the data is committed to cache. DMA write addresses are compared to addresses in this second victim buffer. On a match the write takes place in the second victim buffer. On a failure to match the controller sends a snoop write.

Abstract: A programmable Built In Self Test (pBIST) system used to test embedded memories where the memories may be operating at a voltage domain different from the voltage domain of the pBIST. A plurality of buffer and synchronizing registers are used to avoid meta stable conditions caused by the time delays introduced by the voltage shifters required to bridge the various voltage domains.

Abstract: A programmable Built In Self Test (pBIST) system used to test embedded memories where the memories under test are incorporated in a plurality of sub chips not integrated with the pBIST module. A distributed Data Logger is incorporated into each sub chip, communicating with the pBIST over serial and a compressed parallel data paths.

Abstract: This invention handles write request cache misses. The cache controller stores write data, sends a read request to external memory for a corresponding cache line, merges the write data with data returned from the external memory and stores merged data in the cache. The cache controller includes buffers with plural entries storing the write address, the write data, the position of the write data within a cache line and unique identification number. This stored data enables the cache controller to proceed to servicing other access requests while waiting for response from the external memory.

Abstract: This invention assures cache coherence in a multi-level cache system upon eviction of a higher level cache line. A victim buffer stored data on evicted lines. On a DMA access that may be cached in the higher level cache the lower level cache sends a snoop write. The address of this snoop write is compared with the victim buffer. On a hit in the victim buffer the write completes in the victim buffer. When the victim data passes to the next cache level it is written into a second victim buffer to be retired when the data is committed to cache. DMA write addresses are compared to addresses in this second victim buffer. On a match the write takes place in the second victim buffer. On a failure to match the controller sends a snoop write.

Abstract: A programmable Built In Self Test (pBIST) system used to test embedded memories where the memories under test are incorporated in a plurality of sub chips not integrated with the pBIST module. Test data comparison is performed in a distributed data logging architecture to minimize the number of interconnections between the distributed data loggers and the pBIST.

Abstract: A method to eliminate the delay of multiple overlapping block invalidate operations in a multi CPU environment by overlapping the block invalidate operation with normal CPU accesses, thus making the delay transparent. The cache controller performing the block invalidate operation merges multiple overlapping requests into a parallel stream to eliminate execution delays. Cache operations other that block invalidate, such as block write back or block write back invalidate may also be merged into the execution stream.

Abstract: This invention is a means to definitively establish the occurrence of various clock edges used in a design, balancing clock edges at various locations within an integrated circuit. Clocks entering from outside sources can be a source of on-chip-variations (OCV) resulting in unacceptable clock edge skewing. The present invention arranges placement of the various clock dividers on the chip at remote locations where these clocks are used. This minimizes the uncertainty of the edge occurrence.

Abstract: A programmable Built In Self Test (pBIST) system used to test embedded memories where a plurality of memories requiring different testing conditions are incorporated in an SOC. The pBIST Read Only Memory storing the test setup data is organized to eliminate multiple instances of test setup data for similar embedded memories.

Abstract: Traffic output from a cache write-miss buffer is controlled by determining whether a predetermined condition is satisfied, and outputting an oldest entry from the buffer only in response to a determination that the predetermined condition is satisfied. Posting of a new entry to the buffer is insufficient to satisfy the predetermined condition.

Abstract: Parallel pipelines are used to access a shared memory. The shared memory is accessed via a first pipeline by a processor to access cached data from the shared memory. The shared memory is accessed via a second pipeline by a memory access unit to access the shared memory. A first set of tags is maintained for use by the first pipeline to control access to the cache memory, while a second set of tags is maintained for use by the second pipeline to access the shared memory. Arbitrating for access to the cache memory for a transaction request in the first pipeline and for a transaction request in the second pipeline is performed after each pipeline has checked its respective set of tags.