RE: [t13] 48-bit LBA: Purpose of ID Word 86, bit 10 (vs ID 83, bit 10)

[Eschmann, Michael K]

Title: Message

Steve, why in the world would one bit be off and the other on?  There's no enable/disable control for this feature, so these bits must correlate with each other.   If you allow bit mis-correlation in your drives, I can guarantee you that most drivers will not operate 48-bit commands and the user doesn't get what he payed for.

 

Jeff, I test both bits in word 83 and 86, plus verify that the capacity words are greater than 128GB before I enable 48-bit commands in my driver.  I don't believe that drivers test-run a command during disk enumeration...I know I don't.   Drivers make a choice based on the identify data flags and start sending commands, then clean-up if they fail during run-time.

 

MKE.

 

 

-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Stegmier, Steve
Sent: Wednesday, February 04, 2004 10:03 AM
To: ATA T13 Reflector
Subject: RE: [t13] 48-bit LBA: Purpose of ID Word 86, bit 10 (vs ID 83, bit 10)

 

-----Original Message-----
From: Wolford, Jeff [mailto:[EMAIL PROTECTED]
Sent: Tuesday, February 03, 2004 7:36 PM
To: ATA T13 Reflector
Subject: [t13] 48-bit LBA: Purpose of ID Word 86, bit 10 (vs ID 83, bit 10)

ID Page Word 83, bit 10 indicates support for 48-bit LBA addressing[Stegmier, Steve] s/b Command sets supported 

ID Page Word 86, bit 10 indicates support for 48-bit LBA addressing[Stegmier, Steve] s/b Command set/feature enabled 

 

Q1: Which is it ?[Stegmier, Steve]  Word 83 bit 10 indicates that the device supports the feature (the feature may be enabled or disabled).  Word 86 bit 10 indicates the feature is enabled.

 

Q2: Are both required to be the same value ?[Stegmier, Steve] The bits may be different. 

 

Q2.1: If not the same, does one have priority over the other ?[Stegmier, Steve] If Word 83 bit 10 is off I would not expect to ever see Word 86 bit 10 on. When Word 83 bit 10 is on, Word 86 bit 10 may be off or on.

 

Q3: Does software have to check both bits or is checking Word 83 (and being set)[Stegmier, Steve] Checking Word 86 bit 10 is sufficient.

valid.

 

Thanks,

 

Jeff

 

Jeff Wolford                       Email: [EMAIL PROTECTED]
Master Architect
Storage Interface and Tools - Business PC Group
    Voice: (281) 514-9465,     Pager: (800) 973-5739
Hewlett-Packard Corporation