Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!ucsd!helios.ee.lbl.gov!nosc!crash!pnet01!jca
From: jca@pnet01.cts.com (John C. Archambeau)
Newsgroups: comp.os.minix
Subject: Re: How to get hard disk parameters at boot time
Message-ID: <972@crash.cts.com>
Date: 24 Dec 89 02:56:01 GMT
Sender: root@crash.cts.com
Organization: People-Net [pnet01], El Cajon CA
Lines: 50

yip@ztivax.UUCP (Dr Yeung-Cho Ip) writes:
>
>Sorry for posting this here, but I couldn't reach Bruce through net mail.
>
>Hello Bruce,
>
>in your letter you wrote:
>
>> Where does the controller leave the parameters? I would like to stop Minix
>> overwriting them for version 1.5.
>>
>> I suspect they are being put in the interrupt table (below 0x00400) since
>> Minix doesn't touch (much of) 0x400-0x5FF and everything above there is
>> touched by DOS. 
>
>You're right. The quick and dirty changes I mentioned in my message are nearly
>one and a half year old. Yesterday, I had a closer look on the way our ADAPTEC
>controller works, and I found out that it writes the disk parameters to the
>locations 384 (decimal) upwards.
>
>In addition, I altered the at_wini.c so that it now correctly handels this case
>Since I don't know whether all ADAPTEC and Western Digital
>controllers use the same locations, my approach differs from your
>suggestion. I altered the constant VECTOR_BYTES so that the kernel (main)
>saves the disk parameters to vec_table prior to overwriting them. The
>at_wini then reads the parameters from this table, provided the pointer at 0x41
>points to the low ram lokations.
>
>I will post this new at_wini.c in a few minutes.
>
>Michael
>
>Michael Franzen, c/o yip@ztivax, Siemens AG, Munich


On an IBM AT, one can get the parameters from the CMOS RAM.  This is well
documented in Phoenix's BIOS manual for the AT/XT machines.  (Again, I forget
the title, but the BIOS manual is out there, and everything is well
documented).
 
     // JCA

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