Datasheet
Intel
®
Xeon
®
Processor C5500/C3500 Series
February 2010 Datasheet, Volume 1
Order Number: 323103-001 91
Interfaces
2.2.7.2 Device Discovery
The PECI client is available on all processors, and positive identification of the PECI
revision number can be achieved by issuing the GetDIB() command. The revision
number acts as a reference to the RS - Platform Environment Control Interface (PECI)
Specification, Revision 2.0 document applicable to the processor client definition. See
Section 2.2.2.2 for details on GetDIB response formatting.
2.2.7.3 Client Addressing
The PECI client assumes a default address of 0x30. If nothing special is done to the
processor, all PECI clients will boot with this address. For DP enabled parts, a special
PECI_ID# pin is available to strap each PECI socket to a different node ID. The package
pin strap is evaluated at the assertion of VCCPWRGOOD (as depicted in Figure 30).
Since PECI_ID# is active low, tying the pin to ground results in a client address of
0x31, and tying it to V
TT
results in a client address of 0x30.
The client address may not be changed after VCCPWRGOOD assertion, until the next
power cycle on the processor. Removal of a processor from its socket or tri-stating a
processor in a DP configuration will have no impact to the remaining non-tri-stated
PECI client address.
2.2.7.4 C-States
The Intel
®
Xeon
®
processor C5500/C3500 series PECI client is fully functional under all
core and package C-states. Support for package C-states is a function of processor SKU
and platform capabilities. All package C-states (C1/C1E, C3, and C6) are annotated
here for completeness, but actual processor support for these C-states may vary.
Because the processor takes aggressive power savings actions under the deepest C-
states (C1/C1E, C3, and C6), PECI requests may have an impact to platform power.
The impact is documented below:
• Ping(), GetDIB(), GetTemp() and MbxGet() have no measurable impact on
processor power under C-states.
• MbxSend(), PCIConfigRd() and PCIConfigWr() usage under package C-states may
result in increased power consumption because the processor must temporarily
return to a C0 state in order to execute the request. The exact power impact of a
pop-up to C0 varies by product SKU, the C-state from which the pop-up is initiated,
and the negotiated T
BIT
.
2.2.7.5 S-States
The PECI client is always guaranteed to be operational under S0 and S1 sleep states.
Under S3 and deeper sleep states, the PECI client response is undefined and therefore
unreliable.
Table 47. Power Impact of PECI Commands vs. C-states
Command Power Impact
Ping() Not measurable
GetDIB() Not measurable
GetTemp() Not measurable
PCIConfigRd() Requires a package ‘pop-up’ to a C0 state
PCIConfigWr() Requires a package ‘pop-up’ to a C0 state
MbxSend() Requires a package ‘pop-up’ to a C0 state
MbxGet() Not measurable