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