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2.8.8
MC_RD_CRDT_INIT
These registers contain the initial read credits available for issuing memory reads. TAD
read credit counters are loaded with the corresponding values at reset and anytime this
register is written. BIOS must initialize this register with appropriate values depending
on the level of Isoch support in the platform. It is invalid to write this register while TAD
is active (has memory requests outstanding), as the write will break TAD's outstanding
credit count values.
Register programming rules:
• Total read credits (CRDT_RD + CRDT_RD_HIGH + CRDT_RD_CRIT) must not
exceed 31.
• CRDT_RD_HIGH value must correspond to the number of high RTIDs reserved at
the IOH.
• CRDT_RD_CRIT value must correspond to the number of critical RTIDs reserved at
the IOH.
• CRDT_RD_HIGH + CRDT_RD must be less than or equal to 13.
• CRDT_RD_HIGH + CRDT_RD_CRIT must be less than or equal to 8.
• CRDT_RD_CRIT must be less than or equal to 6. Set CRDT_RD to (16 -
CRDT_RD_CRIT - CRDT_RD_HIGH).
• If (Mirroring OR Sparing enabled) then Max for CRDT_RD is 14, otherwise it is 15.
• If (Isoch not enabled) then CRDT_RD_HIGH and CRDT_RD_CRIT are set to 0.
Device:
Function: 0
Offset:
Access as a Dword
Bit
20:16
12:8
4:0
54
3
70h
Reset
Type
Value
RW
3
CRDT_RD_CRIT. Critical Read Credits.
RW
1
CRDT_RD_HIGH. High Read Credits.
RW
13
CRDT_RD. Normal Read Credits.
Register Description
Description
Datasheet
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