Supermicro X13DDW-A User Manual page 113

IO Directory Cache (IODC)
Select Enable for the IODC to generate snoops instead of generating memory lockups
for remote IIO (InvIToM) and/or WCiLF (Cores). Select Auto for the IODC to generate
snoops (instead of memory lockups) for WCiLF (Cores). The options are Disable, Auto,
Enable for Remote InvItoM Hybrid Push, InvItoM AllocFlow, Enable for Remote InvItoM
Hybrid AllocNonAlloc, and Enable for Remote InvItoM and Remote WViLF.
SNC
Sub NUMA Clustering (SNC) is a feature that breaks up the Last Level Cache (LLC) into
clusters based on address range. Each cluster is connected to a subset of the memory
controller. Enable this feature to improve average latency and reduce memory access
congestion for higher performance. The options are Auto, Disable, Enable SNC2 (2-clus-
ters), and Enable SNC4 (4-clusters).
Note: The option of Enable SNC4 (4-clusters) depends on your system configuration
and the processor.
Stale AtoS (A to S)
Stale AtoS (A to S)
The in-memory directory has three states: I, A, and S states. The I (-invalid) state indi-
cates that the data is clean and does not exist in the cache of any other sockets. The A
(-snoop All) state indicates that the data may exist in another socket in an exclusive or
modified state. The S state (-Shared) indicates that the data is clean and may be shared
in the caches across one or more sockets. When the system is performing "read" on the
memory, and if the directory line is in A state, we must snoop all other sockets because
another socket may have the line in a modified state. If this is the case, a "snoop" will
return the modified data. However, it may be the case that a line "reads" in an A state,
and all the snoops come back with a "miss". This can happen if another socket reads the
line earlier and then has silently dropped it from its cache without modifying it. If "Stale
AtoS" is enabled, a line will transition to the S state when the line in the A state returns
only snoop misses. That way, subsequent reads to the line will encounter it in the S state
and will not have to snoop, saving the latency and snoop bandwidth. Stale "AtoS" may
be beneficial in a workload where there are many cross-socket reads. The options are
Disable, Enable, and Auto.
LLC Dead Line Alloc
Select Enable to opportunistically fill the deadlines in the LLC. The options are Disable,
Enable, and Auto.
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Chapter 4: UEFI BIOS