WG82574L S LBA9 Intel, WG82574L S LBA9 Datasheet - Page 237

• Manufacturer Part Number: WG82574L S LBA9
• Description: CONTROLLER, ENET, INTEL 82574L, 64PQFN
• Manufacturer: Intel

Specifications of WG82574L S LBA9

• Ethernet Type: IEEE 802.3, IEEE 802.3u, IEEE 802.3ab
• Supply Voltage Range: 3V To 3.6V
• Operating Temperature Range: 0°C To +85°C
• Digital Ic Case Style: QFN
• No. Of Pins: 64
• Package / Case: QFN
• Interface Type: I2C, JTAG, PCI, SPI
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

System Manageability—82574 GbE Controller
8.9.7
8.9.8
During the initialization phase, the firmware within the 82574L allocates buffers based
upon the SMBus fragment size setting within the NVM. The 82574L firmware has a
finite amount of RAM for its use, as such the larger the SMBus fragment size, the fewer
buffers it can allocate. As such, the MC implementation must take care to send data
over the SMBus in an efficient way.
For example, the 82574L firmware has 3 KB of RAM it can use for buffering SMBus
fragments. If the SMBus fragment size is 32 bytes then the firmware could allocate 96
buffers of size 32 bytes each. As a result, the MC could then send a large packet of data
(such as KVM) that is 800 bytes in size in 25 fragments of size 32 bytes apiece.
However, this might not be the most efficient way because the MC must break the 800
bytes of data into 25 fragments and send each one at a time.
If the SMBus fragment size is changed to 240 bytes, the 82574L firmware can create
12 buffers of 240 bytes each to receive SMBus fragments. The MC can now send that
same 800 bytes of KVM data in only four fragments, which is much more efficient.
The problem of changing the SMBus fragment size in the NVM is if the MC does not also
reflect this change. If a programmer changes the SMBus fragment size in the 82574L to
240 bytes and then wants to send 800 bytes of KVM data, the MC can still only send the
data in 32 byte fragments. As a result, the firmware runs out of memory.
This is because the 82574L firmware created the 12 buffers of 240 bytes each for
fragments, however the MC is only sending fragments of size 32 bytes. This results in a
memory waste of 208 bytes per fragment in this case, and when the MC attempts to
send more than 12 fragments in a single transaction, the 82574L NACKs the SMBus
transaction due to not enough memory to store the KVM data.
In summary, if a programmer increases the size of the SMBus fragment size in the
NVM, which is recommended for efficiency purposes, take care to ensure that the MC
implementation reflects this change and uses that fragment size to its fullest when
sending SMBus fragments.
Enable XSum Filtering
If XSum filtering is enabled, the MC does not need to perform the task of checking this
checksum for incoming packets. Only packets that have a valid XSum is passed to the
MC, all others are silently discarded.
This is a way to offload some work from the MC.
Still Having Problems?
If problems still exist, contact your field representative. Before contacting, be prepared
to provide the following:
• The contents of status registers:
• A SMBus trace if possible
• A dump of the NVM image
— 0x5820
— 0x5860
— 0x5B54
— This should be taken from the actual 82574L, rather than the NVM image
provided by Intel. Parts of the NVM image are changed after writing, such as
the physical NVM size. This information could be key in helping assist in solving
an issue.
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