Super X12DPG-AR User's Manual
96
IO Directory Cache (IODC)
Select Enable for the IODC (I/O Directory Cache) 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)
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 depending
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 Disable, Enable, 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
allow hardware to enforce peer-to-peer write ordering. The options are
Disable
and Enable.
Stale AtoS (A to S)
The in-memory directory has three states: I, A, and S states. The I (-invalid) state indicates
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
.
