Intel Xeon Processor and Intel E7500/E7501Chipset Compatible Platform Design Guide

Intel
®
Xeon™ Processor and Intel
®
E7500/E7501 Chipset Compatible Platform Design Guide 65
System Bus Routing Guidelines
5.1 Routing Guidelines for the AGTL+ Source
Synchronous 2X and 4X Groups
The 4X group of signals uses four times the frequency of the base clock: 400 MHz or 533 MHz.
The 2X group uses twice the frequency of the base clock: 200 MHz or 266 MHz. The 2X and 4X
signals are listed in Table 5-3. Table 5-4 defines the 2X and 4X signals with their associated
strobes.
Routing guidelines for the 2X and 4X signal groups are given in Table 5-2. All 2X and 4X signals
of the same group (refer to Table 5-4) must be routed within ± 25 mils of the same length between
agents and within ± 50 mils of the entire length of the bus on the same layer.
Warning: AGTL+ Source Synchronous 2X and 4X signals must never change layer: always route the signal
on the same layer for the entire length of the bus.
Table 5-3. 2X and 4X Signal Groups
2X Group 4X Group
A[35:3]#
REQ[4:0]#
HD[63:0]#
DBI[3:0]#
Table 5-4. Source Synchronous Signals with the Associated Strobes
Signals Associated Strobe
REQ[4:0]#, HA[16:3]# ADSTB0#
A[35:17]# ADSTB1#
D[15:0]#, DBI0# DSTBP0#, DSTBN0#
D[31:16]#, DBI1# DSTBP1#, DSTBN1#
D[47:32]#, DBI2# DSTBP2#, DSTBN2#
D[63:48]#, DBI3# DSTBP3#, DSTBN3#