Information Technology Reference
In-Depth Information
Segment Number
Virtual Page Number
Offset
Segment Table
Displacement
Physical Segment Base Address
Σ
Σ
Page Table
Physical Address
Σ
Physical Address
Figure 7.19 Paged segmentation address translation
7.2.10. Pentium Memory Management
In the Pentium processor, both segmentation and paging are individually available
and can also be disabled. Four distinct views of the memory exist:
1. Unsegmented unpaged memory
2. Unsegmented paged memory
3. segmented unpaged memory
4. segmented paged memory
For segmentation, the 16-bit segment number (two of which are used for protection)
and the 32-bit offset produce a segmented virtual address space equal to 2 46
64
terabytes. The virtual address space is divided into two parts: one half, that is,
8K
¼
4 GB, is global and shared by all processes, and the other half is local and
is distinct for each process.
For paging, a two-level table lookup paging system is used. First level is a page
directory with 1024 entries, that is, 1024 page groups, each with its own page table
and each FOUR MB in length. Each page table contains 1024 entries; each entry
corresponds to a single 4 KB page.
 
Search WWH ::




Custom Search