Supermicro X12DPFR-AN6 User Manual page 75

Chapter 4: UEFI BIOS
IO Directory Cache (IODC)
Select Enable for the IODC (I/O Directory Cache) to generate snoops instead of gen-
erating 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)
Select Enable to use "Sub NUMA Clustering" (SNC), which supports full SNC (2-cluster)
interleave and 1-way IMC interleave. Select Auto for 1-cluster or 2-cluster support de-
pending on the status of IMC (Integrated Memory Controller) Interleaving. The options
are Disable and Enable SNC2 (2-clusters).
XPT Prefetch
Select Enable to support XPT (Extended Prediction Table) Prefetch which will allow an
LLC request to be duplicated and sent to an appropriate memory controller based on
the recent LLC history to reduce latency. The options are Enable, Disable, and Auto.
Snoop Throttle Configuration
Use this feature to set the level of snoop throttle for the PCH, which will determine how
much speed to decrease in operation when the system is in the snoop state. The options
are Disabled, Low, Medium, High, and Auto.
PCIe Remote P2P (Peer-to-Peer) Relaxed Ordering
Select Disable to support PCIe remote peer-to-peer relaxed writing ordering, which will al-
low hardware to enforce peer-to-peer write ordering. The options are Enable and Disable.
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
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