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Intel
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82575EB Gigabit Ethernet Controller — Interrupt Control and Tuning
Intel
®
82575EB Gigabit Ethernet Controller 324632-003
Software Developer’s Manual and EEPROM Guide Revision: 2.1
26 January 2011
Table 2. Intel® Architecture Byte Ordering
Note: The notation in this manual follows the convention shown in Table 2. For example, the
address in Table 2 indicates 00_AA_00_11_22_33h, where the first byte (00h_) is the first
byte on the wire, with bit 0 of that byte transmitted first.
2.4 Interrupt Control and Tuning
The 82575 provides a complete set of interrupts that allow for efficient software management. The
interrupt structure is designed to accomplish the following:
• Make accesses “thread-safe” by using ‘set’ and ‘clear-on-read’ rather than ‘read-modify-write’
operations.
• Correlate between related bits in different registers (for example, ICR)
• Minimize the number of interrupts needed relative to work accomplished.
• Minimize the processing overhead associated with each interrupt.
The interrupt logic consists of the interrupt registers that are described in sections 14.3.34 through
14.3.37.
Two actions minimize the number of interrupts:
1. Reducing the frequency of all interrupts
2. Accepting multiple receive packets before signaling an interrupt.
One interrupt register consolidates all interrupt information eliminating the need for multiple accesses.
Note: The 82575 supports Message Signaled Interrupts per the PCI 2.2, 2.3, and PCIe*
specifications. See Section 4.7.5.1 for details.
2.5 Hardware Acceleration Capability
The 82575 provides the ability to offload IP, TCP, and UDP checksum for transmit. The functionality
provided by these features can significantly reduce processor utilization by shifting the burden of the
functions from the driver to the hardware. Features include:
• Jumbo frame support
• Receive and transmit checksum offloading
• TCP segmentation
• Receive fragmented UDP checksum offload
• These features are briefly outlined in the following sections.
IA Byte # 1 (LSB) 2 3 4 5 6 (MSB)
Byte Value (Hex) 00 AA 00 11 22 33