Dell PowerEdge M820 (for PE VRTX) - Manual (Page 56)

Table 2. Processor and heat sink configurations
Processor
Configuration
Processor
Type (in
Watts)
Heat
Sink
Number of DIMMs
Maximum
Reliability, Availability, and
Serviceability (RAS) Features
Two processors Up to 95
W
67 mm 24 (Three DIMMs per
channel)
24 (Three DIMMs per channel)
Two processors Above 95
W
87 mm 20 (Three DIMMs in
channels 0 and 3 and two
DIMMs in channels 1 and
2)
16 (Two DIMMs per channel)
Four processors Up to 95
W
67 mm 48 48
Four processors Above 95
W
87 mm 40 (Three DIMMs in
channels 0 and 3 and two
DIMMs in channels 1 and
2)
32 (Two DIMMs per channel)
Mode-specific guidelines
Four memory channels are allocated to each processor. The allowable configurations depend on the
memory mode selected.
NOTE: x4 and x8 DRAM based DIMMs can be mixed providing support for RAS features. However,
all guidelines for specific RAS features must be followed. x4 DRAM based DIMMs retain Single
Device Data Correction (SDDC) in memory optimized (independent channel) mode. x8 DRAM based
DIMMs require Advanced ECC mode to gain SDDC.
The following sections provide additional slot population guidelines for each mode.
Advanced ECC (lockstep)
Advanced ECC mode extends SDDC from x4 DRAM based DIMMs to both x4 and x8 DRAMs. This
protects against single DRAM chip failures during normal operation.
Memory installation guidelines:
• Memory modules must be identical in size, speed, and technology.
• DIMMs installed in memory sockets with white release levers must be identical and similar rule applies
for sockets with black release levers. This ensures that identical DIMMs are installed in matched pairs -
for example, A1 with A2, A3 with A4, A5 with A6, and so on.
NOTE: Advanced ECC with Mirroring is not supported.
Memory optimized (independent channel) mode
This mode supports SDDC only for memory modules that use x4 device width, and the mode does not
impose any specific slot population requirements.
Memory sparing
NOTE: To use memory sparing, this feature must be enabled in the System Setup.
In this mode, one rank per channel is reserved as a spare. If persistent correctable errors are detected on
a rank, the data from this rank is copied to the spare rank and the failed rank is disabled.
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