摘要:
A queuing requester for access to a memory system. Transaction requests received from two or more requestors access to the memory system. Each transaction request includes an associated priority value. A request queue is formed in the queuing requester. Each transaction request includes an associated priority value. A highest priority value of all pending transaction requests within the request queue is determined. An elevated priority value is selected when the highest priority value is higher than the priority value of an oldest transaction request in the request queue; otherwise the priority value of the oldest transaction request is selected. The oldest transaction request in the request queue with the selected priority value is then provided to the memory system. An arbitration contest with other requesters for access to the memory system uses the selected priority value.
摘要:
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.
摘要:
A system and method of optimized user coherence for a cache block with sparse dirty lines is disclosed wherein valid and dirty bits of each set are logically AND'ed together and the result for multiple sets are logically OR'ed together resulting in an indication whether a particular block has any dirty lines. If the result indicates that a block does not have dirty lines, then that entire block can be skipped from being written back without affecting coherency.
摘要:
This invention is an exception priority arbitration unit which prioritizes memory access permission fault and data exception signals according to a fixed hierarchy if received during a same cycle. A CPU memory access permission fault is prioritized above a DMA memory access permission fault of a direct memory access permission fault. Any memory access permission fault is prioritized above a data exception signal. A non-correctable data exception signal is prioritized above a correctable data exception signal.
摘要:
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.
摘要:
This invention is a memory system with parity generation which selectively forms and stores parity bits of corresponding plural data sources. The parity generation and storage depends upon the state of a global suspend bit and a global enable bit, and parity detection/correction corresponding to each data source.
摘要:
This invention is a data processing system including a central processing unit, an external interface, a level one cache, level two memory including level two unified cache and directly addressable memory. A level two memory controller includes a directly addressable memory read pipeline, a central processing unit write pipeline, an external cacheable pipeline and an external non-cacheable pipeline.
摘要:
This invention is an exception priority arbitration unit which prioritizes memory access permission fault and data exception signals according to a fixed hierarchy if received during a same cycle. A CPU memory access permission fault is prioritized above a DMA memory access permission fault of a direct memory access permission fault. Any memory access permission fault is prioritized above a data exception signal. A non-correctable data exception signal is prioritized above a correctable data exception signal.
摘要:
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.
摘要:
The invention is a memory system having two memory banks which can store and recall with memory error detection and correction on data of two different sizes. For writing separate parity generators form parity bits for respective memory banks. For reading separate parity detector/generators operate on data of separate memory banks.