SAS 1,5 Gbps maximum voltage level change?

Alvin.Cox at Alvin.Cox at
Tue May 20 08:07:13 PDT 2003

* From the T10 Reflector (t10 at, posted by:
* Alvin.Cox at

SAS currently specifies 1200mV pk-pk as the maximum voltage for 1,5 Gbps
internal signals. SATA has adopted the SAS external level of 1600mV pk-pk
maximum for both 1,5 and 3,0 Gbps applications for external and backplane
applications (Gen1x, Gen2x). Talking with people from various companies
involved with both SAS and SATA PHY work, it would be possible to increase
the SAS 1,5 Gbps level to 1600mV maximum to have consistency in both SAS
and SATA specifications without significant hardware impact. I am concerned
that SATA and SAS will be different if a 1600mV pk-pk SATA product at 1,5
Gbps for backplane applications is made available (Gen1x) and the SAS
specification is not changed.

Bottom line: Can we take action to increase the SAS 1,5 Gbps maximum signal
level to 1600mV pk-pk at this stage of the specification? It doesn't appear
to be an issue from a hardware standpoint since SAS products will primarily
target the 3,0 Gbps which are allowed to transmit at this level. Comments
are encouraged.

Alvin Cox
Seagate Technology, LLC
Tel 405-324-3413
Fax 405-324-4222
Cell 405-206-4809
E-Mail  alvin.cox at

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