AT&T 3B2/300 Technical Reference Manual page 305

FUNCTIONAL D E S C R I P T I O N - - - - - - - - - - - - - - - - - - - - - - - - - - -
Virtual to Physical Address Translation for Contiguous Segments.
Figure 3-18 shows the
translation of a virtual address to a physical address for a contiguous segment of physical memory. The
Section Identification (SID) field is used to find the base address of the required Segment Descriptor
Table (SOT). The base address of the SOT for each section is stored in the MMU. This base address
and the Segment Select (SSL) field are combined to index a Segment Descriptor (SD) within the SOT.
This address is added to the Segment Offset (SOT) field to form the required physical address.
Virtual to Physical Address Translation for Paged Segments.
Figure 3-19 shows the translation
of a virtual address to a physical address for a paged segment of physical memory. The SID field is
used to find the base address of the required SOT. The base address of the SOT for each section is
stored in the MMU. This base address and the SSL field are combined to index an SD within the SOT.
The SD is used as the base address of a Page Descriptor Table (PDT). This PDT address is combined
with the Page Select (PSL) field to index a Page Descriptor (PD). The PD contains the starting address
of the paged segment that is concatenated with the Page Offset (POT) field to form the required
physical address.
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