8. Performance > Configuring the Tsi578 for Performance Measurements
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Tsi578 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
8.3
Configuring the Tsi578 for Performance Measurements
Performance measurements for complex traffic patterns can be specified for two different
configurations of performance settings.
The first configuration is for lightly loaded systems, where the likelihood of resource contention is low.
This is known as the ‘fair share’ performance configuration.
The second configuration is for congested systems which optimize the throughput and latency of the
highest priority packets at the expense of lower priority packets. This is known as the ‘high priority’
performance configuration.
There are many controls in the Tsi578 that allow a system designer to optimize their system
interconnect performance. These controls can be categorized as clock speeds, ISF arbitration settings,
RapidIO packet scheduling and buffer management settings.
8.3.1
Clock Speeds
Port speeds directly affect throughput, latency and latency variation. Generally, the slower the port, the
lower the throughput, the higher the average latency and the greater the spread between minimum and
maximum latency.
•
For ports operating in 1x mode, performance measurements are specified for operation at 3.125
Gbaud.
•
For ports operating in 4x mode, performance measurements are specified for operation at 3.125
Gbaud per lane.
•
All performance measurements assume that the ISF is operating at its maximum frequency of
156.25 MHz.
8.3.2
Tsi578 ISF Arbitration Settings
The ISF has three possible settings for its egress arbitration: First Come, First Served, Strict Priority 1,
and Strict Priority 2.
The First Come, First Served algorithm is used in the
fair share
performance configuration.
For
high priority
systems which require the absolute lowest possible latency for the highest priority
packets, and are willing to tolerate the additional latency and latency variation induced on the lower
priority packets, the ISF Strict Priority 2 arbitration algorithm should be used. ISF Strict Priority 1 can
be used in verification to ensure that ISF Strict Priority 2 does deliver optimal performance.
Ti
p
It is expected that configurations different from the two described will have performance
figures between the two values specified.
Ti
p
Performance changes linearly with port and ISF speed.