On 10/13/2010 01:00 PM, H. Peter Anvin wrote:
On 10/13/2010 12:17 PM, H. Peter Anvin wrote:
The ACPI specification recognizes three interfaces as standard: PC/AT (64 bytes, even though 128 bytes is available on a lot of platforms), PIIX4 (256 bytes), and Dallas Semiconductor ("256 bytes or more"). The interface for the latter isn't well cited in the ACPI spec, but I'm guessing this is referring to the DS17885 series of chips, which can have up to 8K CMOS using a bank-switched scheme which presents 128 bytes at a time (thus accessible via only the standard 70/71 ports.)
FWIW, the DS17885 scheme actually allows addressing up to 64K; 8K is the maximum that DS produced with this particular interface as far as I know, but there are 16 address bits available.
-hpa
I think this is the relevant application note:
http://www.maxim-ic.com/app-notes/index.mvp/id/77
-hpa