The Unabridged Pentium 4 IA32 Processor Genealogy

Finding the Location of a Physical Page

Find the Page Table First

Refer to Figure 12-6 on page 223 during the following discussion. When the 32- bit linear address is supplied to the Paging Unit by the segment unit, the upper ten bits, [31:22], identify the target page group. The 10-bit group number is used to index into the Page Directory, selecting 1 of up to 1024d Page Tables. Since each Page Directory Entry (PDE) is four bytes long, the Paging Unit multiplies the index by four to create the offset into the Page Directory. It then adds the resulting offset to the Page Directory Base Address (from CR3) to create the start address of the PDE in physical memory. The entry is read from memory and the Page Table Present bit (bit zero) is tested ...