Intel SR1680MV - Server System - 0 MB RAM, Service Manual

Page: 39 / 196

Intel
®
Server System SR1680MV Service Guide 19
System Memory Channel Population Requirements for
Memory RAS Modes
The rules on channel population and channel matching vary by the RAS mode used. There
are three different memory RAS modes: Independent Channel Mode, Mirrored Channel
Mode, and Lockstep Channel Mode.
Note: Mirrored Channel Mode and Lockstep Channel Mode require matching populations that
the same slot positions across channels must hold the same DIMM type with regards to
size and organization.
Independent Channel Mode
Channels can be populated in any order in this mode. All these channels may be populated
in any order and have no matching requirements. All channels must run at the same
interface frequency but individual channels may run at different DIMM timings (RAS
latency, CAS latency, and so forth).
Mirrored Channel Mode
In Mirrored Channel Mode, the memory contents are mirrored between Channel 0 and
Channel 1. As a result of the mirroring, the total physical memory available to the system
is half of what is populated. Mirrored Channel Mode requires that Channel 0 and Channel
1 must be populated identically with regards to size and organization. DIMM slot
populations within a channel do not have to be identical but the same DIMM slot location
across Channel 0 and Channel 1 must be populated the same. Channel 2 is unused in
Mirrored Channel Mode.
Lockstep Channel Mode
In Lockstep Channel Mode, each memory access is a 128-bit data access that spans
Channel 0 and Channel 1. Lockstep Channel mode is the only RAS mode that supports x8
SDDC. Lockstep Channel Mode requires that Channel 0 and Channel 1 must be populated
identically with regards to size and organization. DIMM slot populations within a channel
do not have to be identical but the same DIMM slot location across Channel 0 and
Channel 1 must be populated the same. Channel 2 is unused in Lockstep Channel Mode.
For your reference, Table 3 offers an ideal DIMM population option for A-F channels of
processor 1 and 2. The last column in tables marks DIMM installation under Mirrored
Channel Mode for your reference.