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Date: Wed, 13 Oct 2010 13:22:25 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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Subject: Re: [SeaBIOS] [Qemu-devel] [RFC] Passing boot order from qemu to
	seabios
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To: Gleb Natapov <gleb@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, seabios@seabios.org, qemu-devel@nongnu.org

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