Host_Clk[1:0]# Routing Guidelines - Intel Xeon Design Manual

Table 4-3. HOST_CLK[1:0]# Routing Guidelines
HOST_CLK Skew between Agents
Trace Width
Differential Pair Spacing
Spacing to Other Traces
Serpentine Spacing
Motherboard Impedance – Differential
Motherboard Impedance – Single Ended
Processor Routing Length –
L1, L1': Clock Driver to Rs
Processor Routing Length –
L2, L2': Rs to Rs-Rt Node
Processor Routing Length –
L3, L3': Rs-Rt Node to Rt
Processor Routing Length –
L4, L4': Rs-Rt Node to Load
MCH Routing Length –
L1, L1': Clock Driver to Rs
MCH Routing Length –
L2, L2': Rs to Rs-Rt Node
MCH Routing Length –
L3, L3': Rs-Rt Node to Rt
MCH Routing Length –
L4, L4': Rs-Rt Node to Load
Processor to MCH Length Matching (LT)
Processor to Processor Length Matching (LT)
HOST_CLK0 – HOST_CLK1 Length Matching ± 10 mils
Rs Series Termination Value
Rt Shunt Termination Value
NOTES:
1. The skew budget includes clock driver output pair to output pair jitter (differential jitter) and skew, clock skew
due to interconnect process variation, and static skew due to layout differences between clocks to all bus
agents.
2. This number does not include clock driver common mode (cycle to cycle) jitter or spread spectrum clocking.
3. The interconnect portion of the total budget for this specification assumes clock pairs are routed on multiple
routing layers and routed no longer than the maximum recommended lengths.
Design Guide
Layout Guideline
Platform Clock Routing Guidelines
Value
300 ps total budget:
150 ps for clock driver
150 ps for interconnect
5 mils
20 – 25 mils
25 mils
Maintain a minimum S/h ratio
of > 5/26
Keep parallel serpentine
sections as short as possible.
Minimize 90 degree bends.
Make 45 degree bends, if
possible.
Ω
100 typical
Ω
50 ± 10%
0 – 0.5"
0 – 0.2"
0 – 0.2"
0 – 22"
0 – 0.5"
0 – 0.2"
0 – 0.2"
0 – 22"
0.035" ± 0.010"
MCH LT must be 0.076"
longer than Processor LT.
± 10 mils
Ω
± 5%
20 – 33
Ω
± 1%
49.9
Ω
(for 50 board impedance)
Illustration Notes
Figure 4-2
and 1,2,3,4
Figure 4-3
Figure 4-4
Figure 4-4 5,6
Figure 4-4
Figure 4-4
8
9
Figure 4-2 13
Figure 4-2 13
Figure 4-2 13
Figure 4-2
Figure 4-2 13
Figure 4-2 13
Figure 4-2 13
Figure 4-2
Figure 4-2 10
Figure 4-2 15
Figure 4-2 11
Figure 4-2 12
39