Electrical Specifications
Figure 2-3. Overshoot Example Waveform
VOS
VID + 0.050
VID - 0.000
TOS
0
5
10
15
20
25
Time [us]
TOS: Overshoot time above VID
VOS: Overshoot voltage above VID
2.5
Intel® QPI and Intel® Scalable Memory
Interconnect (Intel® SMI) Interface Differential
Signaling
The Intel Xeon Processor E7-8800/4800/2800 Product Families processor Intel QPI and
Intel® Scalable Memory Interconnect (Intel® SMI) signals use differential links. The
termination voltage level for the Intel Xeon Processor E7-8800/4800/2800 Product
Families processor for uni-directional serial differential links, each link consisting of a
pair of opposite-polarity (D+, D-) signals is VSS.
Termination resistors are provided on the processor silicon and are terminated to VSS.
Intel chipsets also provide on-die termination (ODT), thus eliminating the need to
terminate the links on the system board for the Intel QPI and Intel SMI signals.
Figure 2-4 illustrates the active ODT. Signal listings are included in Table 2-3 and
Table 2-4.
See Chapter 5 for the pin signal definitions. All of the signals on the processor Intel QPI
and Intel SMI signals are in the differential signal group.
Figure 2-4. Active ODT for a Differential Link Example
TX
RX
Signal
Signal
RTT
RTT
RTT
RTT
26
Datasheet Volume 1 of 2
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