Abstract: In a data processing system comprising a first cache operable to store data for use when performing a data processing operation, and a second cache operable to store data required for fetching data into the first cache from memory, when it is determined that there is no entry for data for a data processing operation in the first cache, an entry in the first cache is allocated for the required data, and information that indicates an entry in the second cache for data required for fetching the required data is stored in the tag portion of the allocated entry. Then, once a request has been sent to a memory system for the required data, the information in the tag portion for the allocated entry in the first cache that indicates an entry in the second cache is replaced with information indicative of an address for the data required for fetching the required data.

Abstract: In a data processing system in which varying numbers of channels for accessing a memory can be configured, the communications channel to use for an access to the memory is determined by mapping a memory address associated with the memory access to an intermediate address within an intermediate address space, selecting, based on the number of channels configured for use to access the memory, a mapping operation to use to determine from the intermediate address which channel to use for the memory access, and using the selected mapping operation to determine from the intermediate address which channel to use for the memory access.