Once the correct page table is found, the page table entry is consulted and the usual mechanism of examining the present/absent bit, the dirty bit and other data is invoked. If the page is not in RAM, a page fault occurs. If the page table is full, a victim must be found.

Speed is obviously sacrificed by having a two-layer virtual memory such as this. Some chips even have more than 2 levels! But the principle of locality saves the day, along with a translation lookaside buffer to remember the most recently translated addresses. See section 12.7 for details. In a segmented paged virtual memory, such as the one in Fig. 12.10.1, the combination of segment number/page number is used as the search key, with the actual frame number of RAM being the result. Then the offset within the page is tacked onto the end.