Intel E7-4830 AT80615007089AA Manual Do Utilizador
Códigos do produto
AT80615007089AA
Datasheet Volume 2 of 2
27
Home Agent and Global Coherence Engine (Bbox)
Note:
TID Assignment Restrictions have been updated for modes 4, 5, 6, and 7.
5.2
Directory Assisted Snoopy (DAS)
DAS stands for Directory Assisted Snoopy. It enables early data return from Home
(BBox) to Requestor (Caching agent), without waiting for peer snoop responses if
directory state for the requested line indicates that no peer socket has the line. DAS is
enabled only for local socket request. For enabling DAS (for local socket) we have
introduced a new directory state known as Remote State (or R state). Intel Xeon
processor 7500 series only had two directory states namely I state (Idle state) or E
state (owned by IOH). In Intel Xeon Processor E7-8800/4800/2800 Product Families, R
state is also introduced. These 3 state are defined in Intel Xeon Processor E7-8800/
4800/2800 Product Families as:
(BBox) to Requestor (Caching agent), without waiting for peer snoop responses if
directory state for the requested line indicates that no peer socket has the line. DAS is
enabled only for local socket request. For enabling DAS (for local socket) we have
introduced a new directory state known as Remote State (or R state). Intel Xeon
processor 7500 series only had two directory states namely I state (Idle state) or E
state (owned by IOH). In Intel Xeon Processor E7-8800/4800/2800 Product Families, R
state is also introduced. These 3 state are defined in Intel Xeon Processor E7-8800/
4800/2800 Product Families as:
• I state: Line is either not present in any caching agent or is owned by local socket
caching agent, but definitely not present in any remote socket/IOH.
• R state: Line may be present in a remote socket.
• E (or D) state: Line is owned by IOH.
• E (or D) state: Line is owned by IOH.
If DAS is enabled and local socket sends a read request (RdData/RdInvown), BBox
does a MemRead (basically a prefetch) and directory bits (received with prefetch ack
from Mbox) indicates I state, then data can be send to the requesting local socket even
before all the peer snoop responses have been received. DAS is a very significant
performance feature for 8 socket systems and NC based topologies which are limited
by snoop bandwidth (that is, where idle read latency is snoop limited and not Memory
latency limited).
does a MemRead (basically a prefetch) and directory bits (received with prefetch ack
from Mbox) indicates I state, then data can be send to the requesting local socket even
before all the peer snoop responses have been received. DAS is a very significant
performance feature for 8 socket systems and NC based topologies which are limited
by snoop bandwidth (that is, where idle read latency is snoop limited and not Memory
latency limited).
DAS is only supported in hemisphere mode and not in non-hemisphere mode.
DAS is not supported with mirroring.
5.3
IO Directory Cache (IODC)
IO Directory Cache (IODC) is a new feature for Intel Xeon Processor E7-8800/4800/
2800 Product Families. The aim of this feature is to improve Streams throughput by
eliminating directory reads for InvItoE from snoopy caching agents.
2800 Product Families. The aim of this feature is to improve Streams throughput by
eliminating directory reads for InvItoE from snoopy caching agents.
We Implement a 64 entry directory cache to complement directory in memory.
This feature leverages 2 IOH properties:
• IOH can only get ownership of a line via InvItoE.
• IOH can only own as many lines as it has RTIDs.
• IOH can only own as many lines as it has RTIDs.
IOH takes ownership of the line by issuing an InvItoE. This exclusive ownership phase
(started by IOH issuing an InvItoE and ends in BBox sending GntE_CMP) is almost
immediately followed by WriteBack Phase.
(started by IOH issuing an InvItoE and ends in BBox sending GntE_CMP) is almost
immediately followed by WriteBack Phase.
5
8S HemiSphere + 4 IOH/XNC
TID [0...31],TID[0..15]
TID [0...15]
6
4S Hemisphere + 2 IOH/XNC
TID [0…63], TID [0…31]
TID [0...31]
7
4S Non-Hemisphere + 2 IOH/XNC
TID [0…31], TID [0…15]
TID [0...31]
Table 5-2.
TID Assignment Restrictions (Sheet 2 of 2)
Mode
Configuration
Sboxes
IOH/XNCs