Intel 855GME

308
Intel
®
855GME Chipset and Intel
®
6300ESB ICH Embedded Platform Design Guide
Layout Checklist
SDQ[71:0]
SDM[8:0]
SDQS[8:0]
• See a detailed discussion on this topic in
Section 5.4.4
• Route SDQ/SDM with trace impedance
55
Ω ± 15% using 2:1 spacing.
• Route SDQS strobes similarly with 3:1
spacing.
• Isolation from non-DDR signals should be
20 mils.
• Overall min/max length to the DIMM must
comply with clock length matching
requirements.
• The full data bus SDQ[63:0], mask bus
SDM[7:0], and strobe signals SDQS[7:0]
should be routed on the same internal
signal layer.
• It is required that the SDQ byte group and
the associated SDM and SDQS signals
within a byte lane be routed on the same
internal layer.
• Maximum recommended via count per
signal is 6.
• Refer to the detailed routing
guidelines in Section 5.4.4.
SCKE[3:0]
SCS[3:0]#
• See a detailed discussion on this topic in
Section 5.4.5
• Route with trace impedance 55
Ω ± 15%
using 2:1 spacing.
• Isolation from non-DDR signals should be
20 mils.
• GMCH pad to DIMM trace length limits are
2 to 6 inches.
• Place parallel termination resistor within 2
inches of DIMM pad.
• Overall min/max length to the DIMM must
comply with clock length matching
requirements.
• Maximum recommended via count per
signal is 3.
• Refer to the detailed routing
guidelines in Section 5.4.5.
SRAS#
SCAS#
SWE#
SMA[12:6,3,0]
SBA[1:0]
• See a detailed discussion on this topic in
Section 5.4.6.
• Route with trace impedance 55
Ω ± 15%
using 2:1 spacing.
• Isolation from non-DDR signals should be
20 mils.
• GMCH pad to first DIMM trace length
limits are 2 to 5.5 inches.
• Total DIMM to DIMM spacing should be
less than 2 inches.
• Place parallel termination resistor within
1.5 inches of the second DIMM pad.
• Overall min/max length to the DIMM must
comply with clock length matching
requirements.
• Maximum recommended via count per
signal is 6.
• Refer to the detailed routing
guidelines in Section 5.4.6.
Table 149. Intel
®
855GME Chipset GMCH Layout Checklist (Sheet 2 of 6)
Checklist Items Recommendations Comments