Intel E7-8891 v2 CM8063601377422 User Manual

Product codes
CM8063601377422
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Home Agent Functional Description
36
Intel
®
 Xeon
® 
Processor E7-2800/4800/8800 v2 Product Family
Datasheet Volume Two: Functional Description, February 2014
4.1.3
Intel QPI Home Logic
The home logic is responsible for detecting and resolving the coherency conflict and 
memory access ordering for memory accesses. 
4.1.4
Home Agent Data Buffer (HADB)
The HADB is a set of data buffers. It is a temporary storage for transferring the data 
between the ring and memory controller. It has 128 entries, one for each Home Tracker. 
4.1.5
Memory Controller Interface
The interface to MC first decodes the appropriate DRAM channel from the address. This 
process is called “Target Address Decode” (TAD). After the target channel is decoded 
the request is forward to corresponding BGF (bubble generator fifo). On a read, the 
data will be returned from the MC and is forwarded to the HADB. On a write, the data 
will be downloaded from the ring to the HADB and is forwarded to the MC. 
4.2
Directory Support
The HA supports a 2-bit directory which is stored with each cacheline in DRAM ECC bits. 
The directory is used to filter snoops to remote sockets and/or node controllers. The 
directory can reduce the snoop traffic and latency in multiple socket topologies.
4.3
RTID Allocation
Intel QPI specification v1.1 allows each caching agent to be allocated only up to 64 
RTIDs per HA. 
4.4
Backup Tracker (BT)
All home channel messages incoming to the HA will go through the BT (if the BT is 
enabled). The BT maintains a set of FIFOs to order the requests that are waiting to get 
into the HT such that the HT entry is allocated to the oldest waiting request when it 
becomes available.
4.4.1
Backup Tracker Mode
The backup tracker supports 3 different modes below:
• BT_Mode1 is the extended RTID mode for up to 4 sockets which allocates >64 (up 
to 128) BT entries for the local CA and up to 128 BT entries for the remote CAs. 
• BT_Mode2 is the extended RTID mode for 8S configurations which allocates up to 
128 BT entries for the local CA and up to 48 BT entries for the remote CAs.
• BT_Mode3 is the extended RTID mode for 4S+xNC configurations and allows up to 
128 BT entries for the local CA and up to 64 BT entries for the remote CA. 
BT_Mode3 allows for a maximum of 7 CA, and hence cannot be used for 8S.
4.5
NodeID Conventions
Intel Xeon processor E7 v2 product family implements 4-bits of NodeID (NID). Intel 
Xeon processor E7 v2 product family can support up to 2 HAs in each socket. The HAs 
in the same socket will be differentiated by NID[2]. 
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