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Chapter 6 57
Troubleshooting 10/100Base-TX/9000
Performance Troubleshooting
Performance Troubleshooting
This section is intended to provide system administrators or
advanced users with detailed information on how to troubleshoot
performance related problems with the PCI 100BT product.
Below, a few key terms are defined to help in understanding the
troubleshooting information.
Key Terms:
Transmit Threshold:
The transmit threshold value determines how many bytes must be in the
PCI 100BT transmit FIFO before transmission of the bits onto the
ethernet cable will begin.
Transmit Underrun:
A transmit underrun error occurs when the PCI 100BT transmitter
encounters an empty transmit FIFO during the transmission of bits onto
the ethernet cable.
Memory Subsystem Latency:
The memory subsystem latency is defined to be the amount of time it
takes to move data from system memory to an I/O device. This time
includes the arbitration delay for the I/O device and for each bus bridge
between the system memory controller and the I/O device.
Arbitration Delay:
The time it takes an I/O device, or bus bridge to acquire the I/O bus for
data transfer.
Transmit FIFO:
The transmit FIFO is a buffer on the PCI 100BT card used to hold data
transferred from system memory to the PCI 100BT card.
The PCI 100BT product is currently optimized to achieve the best single
card performance. In order to achieve this performance the PCI 100BT
product has set the Transmit Threshold to an aggressive value. The
Transmit Threshold is set so that transmission will begin after 512 bytes