This message is from the T13 list server.
> Now, if we look at the current implementation of checksums, this drive
> would set the top bits to be &EA, rather than &A7, representing 'this
> checksum is valid'.
I think you got it wrong.
A5h (not A7h) means 'checksum is valid'
Both EAh and A7h indicate that bits 7:0 do not represent a valid checksum
(i.e. 'ignore this word')
Thank You !!!
-----------------------------------------------------------------
Jim Hatfield
ATA Interface Firmware & T13 (ATA/ATAPI) Standards Representative
Seagate Technology - PSG
e-mail: [EMAIL PROTECTED]
s-mail: 389 Disc Drive; Longmont, CO 80503 USA
voice: 720-684-2120
fax : 720-684-2711
====================================================
|---------+---------------------------->
| | Andrew Hill |
| | <[EMAIL PROTECTED]|
| | ors.org.uk> |
| | Sent by: |
| | [EMAIL PROTECTED]|
| | rg |
| | No Phone Info |
| | Available |
| | |
| | 02/22/2004 08:32 |
| | AM |
| | Please respond to|
| | andrew.hill |
| | |
|---------+---------------------------->
>--------------------------------------------------------------------------------------------------------------|
|
|
| To: [EMAIL PROTECTED]
|
| cc:
|
| Subject: [t13] Checksum implementation issue
|
>--------------------------------------------------------------------------------------------------------------|
This message is from the T13 list server.
Hiya,
I wrote last night telling you all about my experience with a failed drive.
Interestingly, I've pulled up something which is relevant to the ATA-8
implementation.
The drive which failed was setting the top 16 bits of every word in its
IDENTIFY DEVICE block to be &EA.
Now, if we look at the current implementation of checksums, this drive
would set the top bits to be &EA, rather than &A7, representing 'this
checksum is valid'.
Thus, even if my ATA driver checked for checksums, this drive would have
gotten around this as it would be interpreted as 'checksum invalid'.
May I propose that we introduce a measure in ATA-8 which allows for
potential loss of transmission lines, as well as against total corruption
of the identify block? At the simplest measure, two words set as
010101010101 etc and the following word as 101010101010 etc would test
this.
This drive would successfully evade all anti-fault measures in ATA-7;
definitely an interesting case and worth considering IMHO for ATA-8.
Best wishes,
Drew
--
Signature huh??? Hmm...I dunno...
