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

[Wolford, Jeff]

Title: Message

To the spec writers... we DON'T need two bits to have the exact same meaning...

Quote "man with 2 watches never knows what time it is."

....

 

So I'm still not hearing any place I can site in the ATA spec that says:

 

1) Both bits (word 83 and Word 86 bit 10) have to be the same value.  I'm hearing they "should" but there is no requirement.

I think the driver should check for both bits, but I am looking for a "requirement".... MKE I agree with you, but trying to figure out how to "force" it.

 

2) As far as supported vs enabled, both have the text "supported' and there is no command/set-feature to enable/disable the feature.

 

As far as checking for support, there are several places the ATA spec says you can NOT use values in 100-103 to indicate 48-bit LBA support.

 

3) As far as 48-bit LBA support for capacities < 137GB, several commands REQUIRE 48-bit LBA support (SATA NCQ, Streaming, etc)

 

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

-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Eschmann, Michael K
Sent: Wednesday, February 04, 2004 3:11 PM
To: ATA T13 Reflector
Subject: RE: [t13] 48-bit LBA: Purpose of ID Word 86, bit 10 (vs ID 83, bit 10)

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