This message is from the T13 list server.
Even in SATA, in a PIO Read using the legacy programming interface there's no good way to report a Data FIS error to software, since it already got the ending status before reading the Data register. The checksum might be useful because of that. --- Rob Elliott, HP Server Storage [EMAIL PROTECTED] > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of [EMAIL PROTECTED] > Sent: Tuesday, March 16, 2004 3:05 PM > To: [EMAIL PROTECTED] > Cc: '[EMAIL PROTECTED]'; [EMAIL PROTECTED]; > [EMAIL PROTECTED]; Pat LaVarre > Subject: RE: [t13] Checksum implementation issue > > > This message is from the T13 list server. > > > > > So why would the SATA checksum that happens as part of the > Data D->H FIS > not > > catch an error in transmission? (Obviously such a CRC > assumes that the > > device got the data into the link layer correctly). > > > > Or am I missing something really obvious here? > > Remember, SATA is not the entire world. > Parallel ATA does not have any CRC-like protection for PIO > mode tranfers. > > > 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 > ==================================================== > > > |---------+----------------------------> > | | Mark Overby | > | | <[EMAIL PROTECTED]| > | | om> | > | | Sent by: | > | | [EMAIL PROTECTED]| > | | rg | > | | No Phone Info | > | | Available | > | | | > | | 03/16/2004 03:00 | > | | PM | > | To: "'[EMAIL PROTECTED]'" > <[EMAIL PROTECTED]>, Pat LaVarre | > | <[EMAIL PROTECTED]>, [EMAIL PROTECTED] > | > | cc: > | > | Subject: RE: [t13] Checksum implementation issue > | > > This message is from the T13 list server. > > > So why would the SATA checksum that happens as part of the > Data D->H FIS > not > catch an error in transmission? (Obviously such a CRC assumes that the > device got the data into the link layer correctly). > > Or am I missing something really obvious here? > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Andrew > Hill > Sent: Tuesday, March 16, 2004 1:18 PM > To: Pat LaVarre; [EMAIL PROTECTED] > Subject: Re: [t13] Checksum implementation issue > > This message is from the T13 list server. > > > On 16 Mar 2004 11:40:49 -0700, Pat LaVarre <[EMAIL PROTECTED]> wrote: > > [snip] > > > I can add two points: > > > > 1) > > > > Requiring every bit of the hi byte to toggle once or more during the > > read of Identify "word"s would discover the hi byte stuck, > and might be > > compatible with the ATA/PI 5 specification or a small modification > > thereof. > > > > It would be more efficient to use a register bit to indicate > the presence > of a checksum or CRC though, and also provides a method which could be > applied to oether data-providing commands. > Backwards-compatibility can be > maintained too - all that needs to happen is to ensure that > the signiature > A5 isn't present; setting bit 0 to 0 would be enough, and you > could use > the remaining bits for your CRC / checksum. > > > I'm fairly confident that this has been identified an issue with the > current spec. We've also almost got a proposed modification to suit, > although I admit it does need some of the finer points sorting. > > James, is it possible to run this idea past the committee at the next > meeting? > > Best wishes, > > Drew
