摘要:
A hazard control circuit for a cache controller that prevents overwriting of modified cache data without write back. The cache controller controls a non-blocking, N-way set associative cache that uses a write-back cache-coherency protocol. The hazard control circuit prevents data loss by deferring assignment until after completion of a pending fill for that way. The hazard control circuit of the present invention includes a transit hazard buffer, a stall assertion circuit and a way assignment circuit.
摘要:
Apparatus and method to permit snoop filtering to occur while an atomic operation is pending. The snoop filtering apparatus includes first and second request queues and a cache. The first request queue tracks cache access requests, while the second request queue tracks snoops that have yet to be filtered. The cache includes a dedicated port for each request queue. The first port is dedicated to the first request queue and is a data-and-tag read-write port, permitting modification of both a cache line's data and tag. In contrast, the second port is dedicated to the second request queue and is a tag-only port. Because the second port is a tag-only port, snoop filtering can continue while a cache line is locked without fear of any modification of the data associated with the atomic address.
摘要:
Circuitry including a request queue and a bad address handling circuit. The request queue includes an entry for each outstanding load requesting access to a cache. Each request queue entry includes a valid bit, an issue bit and a flush bit. The state of the valid bit indicates whether or not the associated access request should be issued to the cache. The issue bit indicates whether the load access request has been issued to the cache and the flush bit indicates whether the data retrieved from the cache in response to the request should be loaded into a specified register. The bad address handling circuit responds to a replay load request by manipulating the states of the valid or flush bit of the relevant request queue entry to prevent completion of bad consumer load requests. The bad address handling circuit includes a validation circuit and a flush circuit. The validation circuit alters the state of the valid bit of the relevant request queue entry in response to the replay load request based upon the state of issue bit for that request queue entry. If the issue bit indicates that the load access request has not yet been issued to the cache, then the validation circuit alters the state of the associated valid bit to prevent the issuance of that load access request to the cache. On the other hand, if the bad consumer has already been issued to the cache, then the flush circuit responds by altering the state of the flush bit to prevent the data retrieved from the cache in response to the bad consumer from being loaded into the register file.
摘要:
Apparatus and method for protecting cache data from eviction during an atomic operation. The apparatus includes a first request queue, a second request queue, and an atomic address block. The first request queue stores an entry for each cache access request. Each entry includes a first set of address bits and an atomic bit. The first set of address bits represents a first cache address associated with the cache access request and the atomic bit indicates whether the cache access request is associated with the atomic operation. The second request queue stores an entry for each cache eviction request. Each entry of the second request queue includes a second set of address bits indicating a second cache address associated with the cache eviction request. The atomic address block prevents eviction of a third cache address during the atomic operation on the third cache address. During a first clock cycle the atomic address block receives and analyzes a first set of signals representing a first entry of the first request queue to determine whether they represent the atomic operation. If so, the atomic address block sets a third set of address bits to a value representative of the first cache address. During a second clock cycle during which the atomic operation is being executed the atomic address block receives and analyzes a second set of signals representing the second set of address bits to determine whether the second set of address bits represent a same cache address as the third set of address bits. If so, the atomic address block stalls servicing of the second request queue, thus preventing eviction of data from the cache upon which an atomic operation is being performed.
摘要:
In some embodiments, a power up (or power mode) interface is provided whereby a chip's power up signals are encoded into multiple states to provide more functions than the number of signals used to define the states.
摘要:
A method and system in a data processing system for efficiently interfacing with cache memory by allowing a fetcher to read from cache memory while a plurality of data words or instructions are being loaded into the cache. A request is made by a bus interface unit to load a plurality of instructions or data words into a cache. In response to each individual instruction or data word being loaded into the cache by the bus interface unit, there is an indication that the individual one of said plurality of instructions or data words is valid. Once a desired instruction or data word has an indication that it is valid, the fetcher is allowed to complete a fetch operation prior to all of the instructions or data words being loaded into cache. In one embodiment, a group of invalid tag bits may be utilized to indicate to the fetcher that individual ones of a group of instructions or data words are valid in cache after being written into cache by the bus interface unit.
摘要:
Methods and apparatuses for reducing power consumption of processor switch operations are disclosed. One or more embodiments may comprise specifying a subset of registers or state storage elements to be involved in a register or state storage operation, performing the register or state storage operation, and performing a switch operation. The embodiments may minimize the number of registers or state storage elements involved with the standby operation by specifying only the subset of registers or state storage elements, which may involve considerably fewer than the total number of registers or state storage or elements of the processor. The switch operation may be switch from one mode to another, such as a transition to or from a sleep mode, a context switch, or the execution of various types of instructions.
摘要:
A method and system for saving and/or retrieving context information of a processor core for a power state transition. The processor core resides in a complex power domain variously transitioning between a plurality of power states. The processor core includes a local context storage area for storage and retrieval of processor core context information. A low power context storage resides in a nominal power domain external to the complex power domain. Context information of the processor core is stored to the low power context storage based on whether a power state transition of the complex power domain includes a transition to power down the processor core.
摘要:
In some embodiments, a power up (or power mode) interface is provided whereby a chip's power up signals are encoded into multiple states to provide more functions than the number of signals used to define the states.
摘要:
A non-inclusive multi-level cache memory system is optimized by removing a first cache content from a first cache, so as to provide cache space in the first cache. In response to a cache miss in the first and second caches, the removed first cache content is stored in a second cache. All cache contents that are stored in the second cache are limited to have read-only attributes so that if any copies of the cache contents in the second cache exist in the cache memory system, a processor or equivalent device must seek permission to access the location in which that copy exists, ensuring cache coherency. If the first cache content is required by a processor (e.g., when a cache hit occurs in the second cache for the first cache content), room is again made available, if required, in the first cache by selecting a second cache content from the first cache and moving it to the second cache. The first cache content is then moved from the second cache to the first cache, rendering the first cache available for write access. Limiting the second cache to read-only access reduces the number of status bits per tag that are required to maintain cache coherency. In a cache memory system using a MOESI protocol, the number of status bits per tag is reduced to a single bit for the second cache, reducing tag overhead and minimizing silicon real estate used when placed on-chip to improve cache bandwidth.