A method and system of maintaining coherency for a data block transferred from a main memory to a cache memory. The data transfer is recorded in a tag register in the main memory. An overwrite of the data block is detected by comparing main memory data writes with the recorded transfer. The cache memory is only notified in the event an overwrite is detected. An invalid flag is then set in the cache.
In some embodiments, the invention involves a system and method relating to software caching with bounded-error delayed updates. Embodiments of the present invention describe a delayed-update software-controlled cache, which may be used to reduce memory access latencies and improve throughput for domain specific applications that are tolerant of errors caused by delayed updates of cached values. In at least one embodiment of the present invention, software caching may be implemented by using a compiler to automatically generate caching code in application programs that must access and/or update memory. Cache is accessed for a period of time, even if global data has been updated, to delay costly memory accesses. Other embodiments are described and claimed.
A micro processor emulator in which an SMM flag is set whenever a processor being emulated enters system management mode (SMM) mode, a diminished power mode, and is reset when the processor leaves SMM mode. Events, such as branch instructions, that are recorded in a trace memory while the processor is in SMM mode (when the SMM flag is set) are recorded as a trace frame comprised of a trace word and an associated in system management mode (IN.sub.-- SMM) trace bit. When a user evokes interrogation mode of the emulator, the IN.sub.-- SMM trace bit is used to calculate correct physical addresses for disassembly of the recorded trace information.
A schematic, system, and flowchart to facilitate storage of directory information for a cache coherency protocol. The protocol allows for at least a single bit of directory information overwriting data stored in a cache coherency unit based at least in part on at least one status bit stored in a storage unit. Likewise, the cache coherency protocol determines whether the cache shared.
A method and apparatus is provided for determining and resolving cache conflicts among data arrays that are stored in the main memory of a computer system in which the main memory is coupled with a memory cache that is coupled in turn with a microprocessor. According to the method of the invention, a cache shape vector that characterizes the size and dimension of the cache is determined under computer control. A determination of at least one cache conflict among the arrays stored in the main memory is then determined, in addition to the conflict region in the cache for the conflicting arrays. A padding value is then determined for the arrays stored in the main memory, and the memory locations of the arrays are adjusted in accordance with the padding value to prevent cache conflicts when the data from the conflicting arrays is transferred from the main memory into the cache.
A multi-processor computer system comprising a data storage device, a memory controller, and a plurality of processors. The data storage device has a plurality of memory lines, each memory line having a portion for alternatively storing data or, a set of GONE codes, a count value, and a processor identification code value. A memory controller coupled to the data storage alternatively stores and retrieves data or the GONE code, the count field value and the processor identification code value. At least one of the processors includes a cache memory and a cache memory controller. The cache memory controller compares a GONE code associated with the requested memory line with the contents of the requested memory line, and requests the contents of the requested memory line from a second of the processors in response to the comparison.
