Intel 855GME User Manual

310
Intel
®
855GME Chipset and Intel
®
6300ESB ICH Embedded Platform Design Guide
Layout Checklist
DDR VTT
Decoupling
• Decouple VTT termination rail using one
0603 0.1 µF capacitor per two DDR
signals.
• Spread out placement across the VTT
termination rail, connecting directly to the
rail, so that each parallel termination
resistor is within 100 mils of one of these
high-frequency capacitors.
• Each ground via should be as close to the
associated cap pad as possible, within 25
mils and with as thick a trace as possible.
• Also, place one 4.7 µF ceramic capacitor
on each end of the termination island, and
place one 4.7 µF ceramic capacitor near
the center of the termination island.
• Low frequency bulk decoupling
requirements at the VTT termination rail
should be met with (4) 470 µF caps placed
evenly across the VTT rail, including one
cap at each end.
• Refer to Section 4.8.1.3 for more
information.
Hub Interface
General
Guidelines
• Route hub interface data and strobes with
trace impedance 55
Ω ± 15% using 2:1
spacing and VSS reference.
• Route hub interface strobe and its
complement as a differential pair, length
matched within ± 10 mils.
• Maximum length for both data and strobe
signals is 6 inches.
• Hub interface data and strobe signals are
routed on the same layer, transitioning
together when a layer change is required.
• Keep layer changes to a minimum, using
only 2 vias per net.
• Refer to Section 8.1 for detailed
routing recommendations.
• The platform design guide example
references routing guidelines for the
8-bit Hub Interface using enhanced
(parallel) termination.
Clocks and Reset Signals
BCLK
BCLK#
• For a detailed discussion on this item, see
Section 11.2.1.
• The differential host clock pair should be
length matched to ± 10 mils and to the
processor BCLK/BCLK# pair within
± 20 mils overall (match L1 segments to
± 10 mils across all pairs).
• Route as strip-line traces 4/7 mils spacing
(except as allowed for pin escapes).
• Total length range is 2 to 8.5 inches.
• Refer to host clock group routing
guidelines detailed in Section 11.2.1.
• Refer to Chapter 10 for detailed
breakdown of all system clock
routing recommendations.
Table 149. Intel
®
855GME Chipset GMCH Layout Checklist (Sheet 4 of 6)
Checklist Items Recommendations Comments

Intel 855GME Specifications

General

Brand	Intel
Model	855GME
Category	Computer Hardware
Language	English