摘要:
A memory management and protection system that manages memory access requests from a number of requestors. Memory accesses are allowed or disallowed based on the privilege level of the master, usually a CPU originating the request based on a Privilege Identifier that accompanies each memory access request. Deputy masters such as DMA controllers inherit the Privilege Identifier of the originating master. An extended memory controller selects the appropriate set of segment registers based on the Privilege Identifier to insure that the request is compared to and translated by the segment register associated with the master originating the request.
摘要:
A memory management and protection system that manages memory access requests from a number of requestors. Memory accesses are allowed or disallowed based on the privilege level of the requestor, based on a Privilege Identifier that accompanies each memory access request. An extended memory controller selects the appropriate set of segment registers based on the Privilege Identifier to insure that the request is compared to and translated by the segment register associated with the requestor originating the request. A set of mapping registers allow flexible mapping of each Privilege Identifier to the appropriate access permission. The segment registers translate the logical address from the requestor to a physical address within a larger address space.
摘要:
A memory management and protection system that manages memory access requests from a number of requestors. Memory accesses are allowed or disallowed based on the privilege level of the master, usually a CPU originating the request based on a Privilege Identifier that accompanies each memory access request. Deputy masters such as DMA controllers inherit the Privilege Identifier of the originating master. An extended memory controller selects the appropriate set of segment registers based on the Privilege Identifier to insure that the request is compared to and translated by the segment register associated with the master originating the request.
摘要:
A prefetch cancelation arbiter improves access to a shared memory resource by arbitrarily canceling speculative prefetches. The prefetch cancelation arbiter applies a set of arbitrary policies to speculative prefetches to select one or more of the received speculative prefetches to cancel. The selected speculative prefetches are canceled and a cancelation notification of each canceled speculative prefetch is sent to a higher-level memory component such as a prefetch unit or a local memory arbiter that is local to the processor associated with the canceled speculative prefetch. The set of arbitrary policies is used to reduce memory accesses to the shared memory resource.
摘要:
A prefetch unit includes a program prefetch address generator that receives memory read requests and in response to addresses associated with the memory read request generates prefetch addresses and stores the prefetch addresses in slots of the prefetch unit buffer. Each slot includes a buffer for storing a prefetch address, two data buffers for storing data that is prefetched using the prefetch address of the slot, and a data buffer selector for alternating the functionality of the two data buffers. A first buffer is used to hold data that is returned in response to a received memory request, and a second buffer is used to hold data from a subsequent prefetch operation having a subsequent prefetch address, such that the data in the first buffer is not overwritten even when the data in the first buffer is still in the process of being read out.
摘要:
A memory management and protection system that manages memory access requests from a number of requestors. Memory accesses are allowed or disallowed based on the privilege level of the requestor, based on a Privilege Identifier that accompanies each memory access request. An extended memory controller selects the appropriate set of segment registers based on the Privilege Identifier to insure that the request is compared to and translated by the segment register associated with the master originating the request. A set of mapping registers allow flexible mapping of each Privilege Identifier to the appropriate access permission.
摘要:
This invention allows code emulation in a memory system by implementing a fixed location and size emulation segment that is only accessible to emulation requests, and may be mapped to any area of the physical memory space by the Extended Memory Controller. All areas of the memory space are visible to the emulation process, whether there is a functional segment mapped to that area or not.
摘要:
A prefetch unit generates a prefetch address in response to an address associated with a memory read request received from the first or second cache. The prefetch unit includes a prefetch buffer that is arranged to store the prefetch address in an address buffer of a selected slot of the prefetch buffer, where each slot of the prefetch unit includes a buffer for storing a prefetch address, and two sub-slots. Each sub-slot includes a data buffer for storing data that is prefetched using the prefetch address stored in the slot, and one of the two sub-slots of the slot is selected in response to a portion of the generated prefetch address. Subsequent hits on the prefetcher result in returning prefetched data to the requestor in response to a subsequent memory read request received after the initial received memory read request.
摘要:
A prefetch unit receives a memory read request having an associated address for accessing data that is stored in memory. A next predicted address is determined in response to a prefetch address stored in a slot of an array for storing portions of predicted addresses and associated with a slot in accordance with an order in which a prefetch FIFO counter is modified to select the slots of the array. Data is prefetched from a lower-level hierarchical memory in accordance with a next predicted address and provisioned the prefetched data to minimize a read time for reading the prefetched data. The provisioned prefetched data is read-out when the address of the memory request is associated with the next predicted address.
摘要:
A prefetch filter receives a memory read request having an associated address for accessing data that is stored in a line of memory. An address window is determined that has an address range that encompasses an address space that is twice as large as the line of memory. In response to a determination of in which half the address window includes the requested line of memory, a prefetch direction is to a first direction or to an opposite direction. The prefetch filter can include an array of slots for storing a portion of a next predicted access and determine a memory stream in response to a hit on the array by a subsequent memory request. The prefetch filter FIFO counter cycles through the slots of the array before wrapping around to a first slot of the array for storing a next predicted address portion.