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E
Parameter
Maximum Trace Length
Maximum Stub Length
Distributed Loads
4.1.3.
System AC Parameters: Signal
Quality
The
system
AC
parameters
categories, Signal Quality and
Acceptable signal quality must be maintained over
all
operating
conditions
Figure 23. Receiver Waveform Showing Signal Quality Parameters
PENTIUM® PRO PROCESSOR AT 150, 166, 180, and 200 MHz
Table 19. System Topological Guidelines
To meet a specific clock cycle time, the maximum trace length between any two
agents must be restricted. The flight time (defined later) must be less than or equal
to the maximum amount of time which leaves enough time within one clock cycle
for the remaining system parameters such as driver clock-out delay (T
setup time (T
), clock jitter and clock skew.
SU
All signals should use a Daisy Chain routing (i.e. no stubs). It is acknowledged that
the package of each device on the net imposes a stub, and that a practical layout
using PQFP parts may require SHORT stubs, so a truly stubless network is
impossible to achieve, but any stub on the network (including the device package)
should be no greater than 250 ps in electrical length.
Minimum spacing lengths are determined by hold time requirements and clock
skew. Maintaining 3" ±30% inter-agent spacing minimizes the variation in noise
margins between the various networks, and can provide a significant improvement
for the networks. This is only a guideline.
fall
into
two
Flight
Time.
to
ensure
reliable
Description
operation. Signal Quality is defined by three
parameters: Overshoot/Undershoot, Settling Limit,
and Ringback. These parameters are illustrated in
Figure 23 and are described in Table 20.
), receiver
CO
39
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