The Unabridged Pentium 4 IA32 Processor Genealogy

The Read/Write Check

Assuming that the currently executing program has sufficient privilege to access a page, it is not permitted write access to a page if the page is write-protected. It should be noted, however, that on the 386, a program executing at privilege level 0, 1, or 2 can write to a write-protected page. This issue was addressed on subsequent IA32 processors starting with the advent of the 486 (see “The Write Protect Feature” on page 450).