| 摘要 |
A hierarchical memory structure includes a directory-based main memory coupled to multiple first storage devices, each to store data signals retrieved from the main memory. Ones of the first storage devices are further respectively coupled to second storage devices, each to store data signals retrieved from the respectively coupled first storage devices. Fetch requests to retrieve data signals are issued by ones of the storage devices to the main memory. In response, the main memory determines where the most recent data copy resides, and issues a return request, if necessary to retrieve that copy for the requesting storage device. A speculative return generation logic circuit is coupled to at least two of the first storage devices to intercept the fetch requests. In response to an intercepted request, the speculative return generation logic circuit generates a speculative return request directly to one or more of the other coupled first storage devices. This speculative return request causes any updated copies of the requested data signals that may be stored at a lower level in the hierarchical memory, to be transferred to the first storage device. If a return request for the data is then issued by the main memory in response to the fetch request, the requested data signals are resident in a first storage device, and are readily available to the main memory.
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