On 12/09/2010 02:51 PM, Matthew Garrett wrote:
On Thu, Dec 09, 2010 at 02:40:15PM -0800, H. Peter Anvin wrote:
On 12/09/2010 02:38 PM, Matthew Garrett wrote:
Windows doesn't get validated on old hardware.
XP does this, and older hardware predates the version of the ACPI spec
that introduced this flag.
ACPI is very buggy on early implementations, presumably because WHQL had
not yet been extended to include it. That is exactly why we combine
these kinds of things with a date check.
I'm afraid I don't understand your argument. The date cutoff would be on
the order of 2001 (anything after this will have been tested with XP).
The spec that defines this behaviour only came into existence in August
2000, and any older hardware will be missing the flag that indicates
that this feature is supported. It doesn't seem realistic to believe
that there's any real body of hardware that sets the flag but otherwise
has a broken implementation.
2001 is probably a good date, then.
It's pretty safe you'll see the bit being set on systems which are older
than that, even if it was not defined at the time it was created -- just
being garbage. That's par for the course in BIOS land.
-hpa
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