Length Matching Constraints; Table 49. Signal Group And Signal Pair Names; Table 50. Lvds Signal Trace Length Matching Requirements - Intel 852GM Design Manual

R
The following differential signal groups comprise the LVDS Interface. The topology rules for each
group are defined in subsequent sections.

Table 49. Signal Group and Signal Pair Names

Channel A
Channel B
8.2.1.

Length Matching Constraints

The routing guidelines presented in the following subsections define the recommended routing
topologies, trace width and spacing geometries, and absolute minimum and maximum routed lengths for
each signal group. These recommendations are provided to achieve optimal SI and timing. In addition
to the absolute length limits provided, more restrictive length matching requirements are also provided.
The additional requirements further restrict the minimum to maximum length range of each signal group
with respect to clock strobe, within the overall boundaries defined in the guideline tables, as required to
guarantee adequate timing margins. These secondary constraints are referred to as length matching
constraints. The amount of minimum to maximum length variance allowed for each group around the
clock strobe reference length varies from signal group to signal group depending on the amount of
timing variation that can be tolerated. Refer to Table 50 for LVDS length matching requirements.
Each LVDS channel is length matched to the LVDS strobe signals. The strobes on a given channel are
matched to within ± 25 mils of the target length.

Table 50. LVDS Signal Trace Length Matching Requirements

Signal Group
CHANNEL
A
CHANNEL
B
All length matching formulas are based on GMCH die-pad to LVDS connector pin total length. Package
NOTE:
length tables are provided for all signals in order to facilitate this pad to pin matching.
®
Intel 852GM Chipset Platform Design Guide
Channel
Data pair Signal Matching
IYAM0, IYAP0
IYAM1, IYAP1
IYAM2, IYAP2
IYAM3, IYAP3
IYBM0, IYBP0
IYBM1, IYBP1
IYBM2, IYBP2
IYBM3, IYBP3
Signal Group
Clocks
Data Bus
Clocks
Data Bus
Clock Strobes associated
With the Channel
± 20 mils
± 20 mils
ICLKAM, ICLKAP
± 20 mils
± 20 mils
± 20 mils
± 20 mils
ICLKAM, ICLKAP
± 20 mils
± 20 mils
Integrated Graphics Display Port
Signal Pair Names
ICLKAM, ICLKAP
IYAM[3:0],
IYAP[3:0]
ICLKBM, ICLKBP
IYBM[3:0],
IYBP[3:0]
Strobe Matching
± 25 mils
± 25 mils
135