WG82574L S LBA8 Intel, WG82574L S LBA8 Datasheet - Page 32

• Manufacturer Part Number: WG82574L S LBA8
• Manufacturer: Intel

Specifications of WG82574L S LBA8

• Operating Supply Voltage (typ): 3.3V
• Operating Temp Range: 0C to 85C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 64
• Lead Free Status / RoHS Status: Compliant

3.1.3.8
3.1.3.8.1
3.1.3.8.2
3.1.3.8.3
32
Transaction Attributes
Traffic Class (TC) and Virtual Channels (VC)
The 82574 supports only TC = 0 and VC = 0 (default).
Relaxed Ordering
The 82574 takes advantage of the relaxed ordering rules in PCIe by setting the relaxed
ordering bit in the packet header. The 82574 also enables the system to optimize
performance in the following cases:
Relaxed ordering can be used in conjunction with the no-snoop attribute to enable the
memory controller to advance non-snoop writes ahead of earlier snooped writes.
Relaxed ordering is enabled in the 82574 by setting the RO_DIS bit to 0b in the
CTRL_EXT register.
Snoop Not Required
The 82574 sets the Snoop Not Required attribute bit for master data writes. System
logic can provide a separate path into system memory for non-coherent traffic. The
non-coherent path to system memory provides higher, more uniform, bandwidth for
write requests.
The Snoop Not Required attribute bit does not alter transaction ordering. Therefore, to
achieve maximum benefit from snoop not required transactions, it is advisable to set
the relaxed ordering attribute as well (assuming that system logic supports both
attributes).
Software configures no-snoop support through the 82574’s control register and a set of
NONSNOOP bits in the GCR register in the CSR space. The default value for all bits is
disabled.
The 82574 supports a No-Snoop bit for each relevant DMA client:
All PCIe functions in the 82574 are controlled by this register.
1. TXDSCR_NOSNOOP - Transmit descriptor read.
2. TXDSCW_NOSNOOP - Transmit descriptor write.
3. TXD_NOSNOOP - Transmit data read.
4. RXDSCR_NOSNOOP - Receive descriptor read.
5. RXDSCW_NOSNOOP - Receive descriptor write.
6. RXD_NOSNOOP - Receive data write.
• Relaxed ordering for descriptor and data reads: When the 82574 is a master in a
• Relaxed ordering for receiving data writes: When the 82574 masters receive data
• The 82574 cannot perform relax ordering for descriptor writes or an MSI write.
read transaction, its split completion has no relationship with the writes from the
CPUs (same direction). It should be allowed to bypass the writes from the CPUs.
writes, it also enables them to bypass each other in the path to system memory
because the software does not process this data until their associated descriptor
writes have been completed.
82574 GbE Controller—Interconnects