Specifications

Product Errata 91
Revision Guide for AMD Athlon™ 64 and AMD Opteron™ Processors
25759 Rev. 3.79 July 2009
156 Read Request Incorrectly Generated for Invalid GART Page
Table Entries
Description
When a read request is made to an invalid address within the GART aperture (i.e., when the valid bit
is not set in the GART page table entry), the Northbridge incorrectly generates a read request to the
page specified in the GART page table entry (PTE).
Potential Effect on System
A read request to an arbitrary address may result in undefined behavior.
Suggested Workaround
Operating system software should map a valid guard page after each contiguous region of valid pages
in the aperture. Operating system software should also ensure that the physical page address of all
invalid (unused) GART entries points to a guard page. The guard page should point to a valid physical
page in DRAM; the same physical guard page can be used to guard all allocations and entries. The
placement of the guard page is operating system dependent, but one solution is to assign a value of
0x0 for the physical page address of the guard page.
Fix Planned
No