Abstract: A dynamic address translation (DAT) mechanism which supports virtual memory pages of different sizes with minimal hardware and design impact. The dynamic look-aside table (DLAT) is modified to allow the addition of a second page size to system architecture. In one approach, the DLAT is divided into two sections, one for small (4KB) pages and one for large (1MB) pages. A steering table indicates whether the segment last contained 4KB pages or a 1MB page. As each segment is translated by the DAT mechanism, the page size (1MB or 4KB) contained in the segment is known, and this information is used to select the address bus used for indexing the DLAT. In an alternative approach, the DLAT is not divided into sections; rather, it can interchangeably hold/test/select either of the two different formats in any entry. The steering table dynamically changes the way in which the DLAT is addressed and selects the bits of the entry to be used in the translation.

Abstract: Dynamic address translation structures and procedures are capable of multiple address translations for the same processor in a single cycle. According to one approach, a plurality of directory look aside tables (DLATs) are used to provide multiple address translation. The DLATs are accessed in parallel by separate virtual address generators. To avoid the problem of generating the same address multiple times for each of the DLATs, a generated address for one DLAT may be written to all the DLATs or, alternatively, if a miss occurs in one DLAT, a search is made of the other DLATs before the address is generated. In the former case, an address written to all the DLATs may overwrite an address that will be needed for a future translation by one of the other DLATs. This is avoided in the latter case, but translations in other DLATs are interrupted when a miss occurs in one of the DLATs. This, in turn, may be avoided by employing "shadow" DLATs which are copies of the DLATs.