QG5000XSL9TH Datasheet, PDF (360/458 Pages) Intel Corporation – Intel 5000X Chipset Memory Controller Hub (MCH)

Functional Description
Table 5-16. PCI Express Credit Mapping for Inbound Transactions (Sheet 2 of 2)
Flow Control
Type
Definition
Initial MCH
Advertisement
Inbound Non-
Posted Request
Data Credits
(INPRD)
Tracks the number of non-posted data the agent is capable of
supporting. Each credit accounts for up to 16 bytes of data.
2 (4X)
4 (8X)
8 (16X)
Completion
Header Credits
(CPH) (outbound
request
completions
received at the
MCH)
Tracks the number of completion headers the agent is capable
of supporting.¹
0 (Infinite)
(4) [x4]
(8) [x8]
(16) (x16)
Completion Data
Credits (CPD)
(outbound
request
completions
(data) received at
the MCH)
Tracks the number of completion data the agent is capable of
supporting. Each credit accounts for up to 16 bytes of data.
0 (Infinite)
(8) [x4]
(16) [x8]
(32) [x16]
Notes:
1. Root complexes and end points are permitted to advertise an infinite number of credits for completions.
Though the MCH implements finite queue structures as indicated in bracket for the completions on the inbound
side, by construction, it will never overflow since for each outbound request, the MCH allocates sufficient space
on the inbound side. i.e guarantee by construction
Table 5-17. PCI Express Credit Mapping for Outbound Transactions
Flow Control
Type
Definition
Outbound Posted
Request Header
Credits (OPRH)
Tracks the number of outbound posted requests the agent is
capable of supporting. Each credit accounts for one posted
request.
Outbound Posted
Request Data
Credits (OPRD)
Outbound Non-
Posted Request
Header Credits
(ONPRH)
Outbound Non-
Posted Request
Data Credits
(ONPRD)
Completion
Header Credits
(CPLH) (inbound
request
completions from
MCH)
Completion Data
Credits (CPLD)
(inbound request
completions
(data) from the
MCH)
Tracks the number of outbound posted data the agent is
capable of supporting. Each credit accounts for up to 16 bytes
of data.
Tracks the number of non-posted requests the agent is capable
of supporting. Each credit accounts for one non-posted request.
Tracks the number of non-posted data the agent is capable of
supporting. Each credit accounts for up to 16 bytes of data.
Tracks the number of completion headers the agent is capable
of supporting.
Tracks the number of completion data the agent is capable of
supporting. Each credit accounts for up to 16 bytes of data.
Initial MCH
Advertisement
4(4x)
8(8x)
16(16)
8(4x)
16(8X)
32(16X)
16(4X)
32(8X)
64(16X)
16(4X)
32(8X)
64(16X)
2(x4)
4(x8)
8(x16)
8(x4)
16(x8)
32(x16)
The credit advertisements for the MCH are shown in Table 5-16 and Table 5-17. Every
PCI Express device tracks the above six credit types (inbound) for both itself and the
interfacing device. The rules governing flow control are described in the PCI Express
Base Specification, Revision 1.0a.
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Intel^® 5000X Chipset Memory Controller Hub (MCH) Datasheet