Datasheet

Intel
®
Xeon
®
Processor C5500/C3500 Series
February 2010 Datasheet, Volume 1
Order Number: 323103-001 133
Interfaces
2.6.22.1 Flow Control Credit Return by IIO
After reset, credit information is initialized with the values indicated in Table 76 by
following the flow control initialization protocol defined in the PCI Express Base
Specification, Revision 2.0 . Since the IIO supports only VC0, only this channel is
initialized. As a receiver, the IIO is responsible for updating the transmitter with flow
control credits as the packets are accepted by the Transaction Layer. Credits will be
returned as follows:
• If infinite credits advertised, there are NO Update_FCs for that credit class, as per
spec.
• For non-infinite credits advertised, we have a long timer running that will send
Update_FCs if none was sent in the past say 28 usec (to comply with the spec's
30 usec rule). This 28 us is programmable to 6 us.
• If and only when there is credits to be released, IIO will wait for a configurable/
programmable number of cycles (in the order of 30-70 cycles) before update_FC is
sent. This will be done on a per flow-control credit basis. This mechanism ensures
that credits updates are not sent when there is no credit to be released.
2.6.22.2 FC Update DLLP Timeout
The optional flow control update DLLP timeout timer is supported.
2.6.23 Physical Layer Specifics
2.6.23.1 Polarity Inversion
The PCI Express Base Specification, Version 0.9 of Revision 2.0 defines a concept called
polarity inversion. Polarity inversion allows the board designer to connect the D+ and
D- lines incorrectly between devices. Polarity inversion is supported.
2.6.24 Non-Transparent Bridge
PCI Express non-transparent bridge (NTB) acts as a gateway that enables high
performance, low overhead communication between two intelligent subsystems, the
local and the remote subsystems. The NTB allows a local processor to independently
configure and control the local subsystem, provides isolation of the local host memory
domain from the remote host memory domain while enabling status and data exchange
between the two domains.
See “PCI Express Non-Transparent Bridge” for more information on the NTB.
Non-Posted
Request Data
Credits (NPRD)
Tracks the number of non-posted data the agent is capable of
supporting. Each credit accounts for up to 16 bytes of data.
12 (x4)
24 (x8)
48 (x16)
Completion
Header Credits
(CPH)
Tracks the number of completion headers the agent is capable
of supporting.
6 (x4)
12 (x8)
24 (x16)
Completion Data
Credits (CPD)
Tracks the number of completion data the agent is capable of
supporting. Each credit accounts for up to 16 bytes of data.
12 (x4)
24 (x8)
48 (x16)
Table 77. PCI Express Credit Mapping for Outbound Requests (Sheet 2 of 2)
Flow Control
Type
Definition
Initial IIO
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