ATA/CHS problem (path + new information)

Roman Kurakin rik at
Tue Apr 13 06:07:31 PDT 2004

Bruce Evans wrote:

>On Sun, 11 Apr 2004, Roman Kurakin wrote:
>>I remind you that now I have two problems. First one that FreeBSD uses
>>wrong assumption about which device should be CHS and which LBA:
>>if (!ad_version(atadev->param->version_major) ||
>>!(atadev->param->atavalid & ATA_FLAG_54_58) || !lbasize)
>>atadev->flags |= ATA_D_USE_CHS;
>>True ATA device may not have ATA_FLAG_54_58 valid bit, and also due
>>to last ATA standard this bit is obsoleted.
>>I also want to know why ata driver doesn't check LBA support from word 49?
>>May be this one check could solve my problems and didn't breake code for
>>non-ATA devices.
>Possibly for similar reasons.  It's hard to tell what's in the LBA bit for
>pre-ATA devices older than LBA.  Similarly for the lbasize words, but it's
>easier to do a sanity check on a 32-bit values that a 1-bit flag.
But since ATA_FLAG_54_58 bit from the fist spec means 1 - "valid" and 0 
- "may be valid"
this check is initialy incorrect. According to ATA-5 it is depricated. 
But in later revisions of
ST380021A  (according to their datasheet, I don't have one) Seagate 
changed this bit to 1
back, I may guess that this was done since probably others uses the same 
check. :-(

Anyway, it seems that Soren already removed this check. So my ST380021A 
should back
to the life.

>>Second one, that only 20G part of my hard disk works with CHS. This is other
>>side of the same problem. Device should work in CHS mode. And it works
>>witch ICH5 controller. But with ICH2 it doesn't with out hack.
>>I've checked standard again and I sew command 91h (Initialize drive
>Check out the commands for limiting the (apparent) disk size.  IIRC,
>the CHS limit can be set independently of the LBA limit, and some
>settings are harder than others so that they can't be cleared by old
>commands like 0x91.  The limits may be set to prevent old drivers which
>only understand old commands from becoming confused by trying to actually
>use the whole disk.
This is good idea. I sew only LBA limits, but I didn't see anytihng 
about CHS limits. I'll try to check
for some more commands.

I can't get how ATA controller could affect on this. Brobably this is 
not controller problem but BIOS,
but changing its settings didn't affect.

Thanks for reply, I hope your suggestions will help me. Since Soren 
removed first bug I'll keep digging
from obstinacy :-)


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