Altera Arria V Avalon-ST - Manual (Page 26)

Parameter Value Description
• Minimum RX Buffer credit allocation -performance for
received requests–This setting configures the minimum
PCIe specification allowed for non-posted and posted
request credits, leaving most of the RX Buffer space for
received completion header and data. Select this option for
variations where application logic generates many read
requests and only infrequently receives single requests
from the PCIe link.
• Low–This setting configures a slightly larger amount of RX
Buffer space for non-posted and posted request credits, but
still dedicates most of the space for received completion
header and data. Select this option for variations where
application logic generates many read requests and
infrequently receives small bursts of requests from the
PCIe link. This option is recommended for typical
endpoint applications where most of the PCIe traffic is
generated by a DMA engine that is located in the endpoint
application layer logic.
• Balanced–This setting allocates approximately half the RX
Buffer space to received requests and the other half of the
RX Buffer space to received completions. Select this option
for variations where the received requests and received
completions are roughly equal.
• High–This setting configures most of the RX Buffer space
for received requests and allocates a slightly larger than
minimum amount of space for received completions. Select
this option where most of the PCIe requests are generated
by the other end of the PCIe link and the local application
layer logic only infrequently generates a small burst of read
requests. This option is recommended for typical root port
applications where most of the PCIe traffic is generated by
DMA engines located in the endpoints.
• Maximum–This setting configures the minimum PCIe
specification allowed amount of completion space, leaving
most of the RX Buffer space for received requests. Select
this option when most of the PCIe requests are generated
by the other end of the PCIe link and the local application
layer logic never or only infrequently generates single read
requests. This option is recommended for control and
status endpoint applications that don't generate any PCIe
requests of their own and only are the target of write and
read requests from the root complex.
2014.12.15
Avalon-ST System Settings 3-3
Parameter Settings Altera Corporation
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