[T10] SAS Maximum SSC frequency deviation

[Kevin D Butt]

Harvey,

Thanks.

Kevin D. Butt
SCSI Architect, Tape Firmware, CAMSS
T10 Standards
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
http://www-03.ibm.com/servers/storage/ 



From:   Harvey Newman <harvey.newman at broadcom.com>
To:     Kevin D Butt/Tucson/IBM at IBMUS
Cc:     Alvin Cox <alvin.cox at seagate.com>, T10 org <t10 at t10.org>, Steve 
Bentley/Tucson/IBM at IBMUS
Date:   04/13/2016 15:06
Subject:        Re: [T10] SAS Maximum SSC frequency deviation



Hi Kevin,

You are correct, a spread of 0.5 % is equal to 5 000 ppm.  This was the 
initial spreading maximum deviation of 5 000 ppm down spreading in other 
standards. With the release of SAS-2 the maximum deviation was reduced to 
2 300 ppm. The release of SAS-3 reduced this further to 1 000 ppm. If you 
open the latest SAS-4 you see a value of 500 ppm (see SAS4r05 Table 43). 

Regards,
Harvey Newman
Broadcom Limited


On Wed, Apr 13, 2016 at 2:53 PM, Kevin D Butt <kdbutt at us.ibm.com> wrote:
I have a question about Maximum SSC frequency deviation (SSCtol) listed in 
Table 73 of SAS-4r05. For 12 Gbit/s the table lists a maximum of -1000 
ppm.

In searching for available clock generators capable of SSC, all parts we 
find provide a minimum of 0.5% spread. By our calculations from the 
standard for -1000 ppm would be equal to -0.1%. Are we misinterpreting the 
spec?

Thanks,

Kevin D. Butt
SCSI Architect, Tape Firmware, CAMSS
T10 Standards
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
http://www-03.ibm.com/servers/storage/

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