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

[Stegmier, Steve]

Title: Message

I was previously speaking in general from the language in the Standard, noting the Identify Device Word 83 is described as "Command set/feature supported" and Word 86 is described as "Command set/feature enabled".  I missed the point that for both words bit 10 is defined as "48-bit feature set supported".  In addition, for a particular Maxtor drive, Word 83 bit 10 and Word 86 bit 10 will either both be cleared or both will be set.

 

 

-----Original Message-----

From: Hale Landis [mailto:[EMAIL PROTECTED]

Sent: Thursday, February 05, 2004 9:57 AM

To: ATA T13 Reflector

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

bit 10)

 

This message is from the T13 list server.

 

In the section titled

"Words (87:85): Feature/command sets enabled"

this is the text description of these words,

(could section 6.16.43 in your copy of ATA/ATAPI-7 Vol 1),

PLEASE SEE THIS SENTENCE:

"If a supported feature/command set is supported and cannot be

disabled, it is defined as supported and the bit shall be set

to one."

LBA48 is such a feature: when supported it can not be disabled.

(End of Discussion?)

Hale

 

*** Hale Landis *** www.ata-atapi.com ***

 

-----Original Message-----
From: Eschmann, Michael K [mailto:[EMAIL PROTECTED]
Sent: Thursday, February 05, 2004 8:56 AM
To: ATA T13 Reflector
Subject: RE: [t13] 48-bit LBA: Purpose of ID Word 86, bit 10 (vs ID 83, bit 10)

Jeff, you are right in that there is no specific "requirement" for both bits to be set, and you see by Maxtor's feedback that the idea of both bits being set is the de-facto "recommended setting" is not shared throughout the industry.

 

I agree that to use advanced features (NCQ, Streaming, etc) you do not have to have a >128GB drive.  But those features aside, existing drivers may just say "do 28-bit commands" if the capacity, or for that matter the current requested LBA range, is below the 28-bit limit just because the 28-bit commands are more "efficient".  Sure, if you want to use these new features the drive has to be 48-bit capable.  I still use the 28-bit commands for basic R/W requests below the 128GB limit.

 

BTW, just in case anyone is confused by the different values that Jeff and I are using to represent the 28-bit capacity limit, the true limit is ~137GB (or 128*(1024^3)) but rounding to 128 is an accepted alternative too because of dividing out 1024^3.

 

So Steve, in light of (some?) drivers requiring both bits set, do you think Maxtor would be interested in setting both in your drives now?  Would there be any resistance to the ATA-8 spec requiring both be set?  This second question is posed to everyone with an opinion.

 

TTFN, MKE.

 

-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Wolford, Jeff
Sent: Wednesday, February 04, 2004 11:40 PM
To: ATA T13 Reflector
Subject: RE: [t13] 48-bit LBA: Purpose of ID Word 86, bit 10 (vs ID 83, bit 10)

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