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Monday, July 19, 2010

Populating DIMMs considerations, Order and Ranks

The Nehalem and Westmere platforms offer a wide variety of DIMM configurations. Some of the various DIMM configurations are shown below

Feature
Values
Number of DIMMs 1,2 or 3
Number of DIMMs slots per channel 2 or 3 DIMM Slots
Number of DIMMs populated per channel 1,2 or 3 DIMM per channel
DIMM Frequencies DDR3-800, DDR3-1066, DDR3-1300
 Table 1:  DIMM Configurations

Populating DIMMs within a channel

When populating DIMMs in a three slots per channel configurations, a “fill-farthest” approach is used, meaning, the farthest DIMM from the processor is used first. If a Quad-rank DIMM is used, it should be populated first.
Figure 1:  DIMM Population within a channel

DIMM population in an 18 DIMM slots configuration

CPU1
CPU2
Slot Number
Population Order
Slot Number
Population Order
Channel1
1
G
1
G
2
D
2
D
3
A
3
A
Channel2
4
H
4
H
5
E
5
E
6
B
6
B
Channel3
7
I
7
I
8
F
8
F
9
C
9
C
 Table 2:  DIMM Population in 18 DIMM Slots

Additional population requirements
  1. All DIMMS must be DDR3 DIMMs.
  2. The 5600 series support low voltage DDR3 memory (DDR3L) 1.35V, the 5500 supports only 1.5V, if mixed they will work at 1.5V.
  3. Mixing Registered and Unbuffered DIMMs is not allowed.
  4. The maximum supported speed is defined by the BIOS and not the DIMMs
  5. Mixing different timing DIMMs will force the operation at the slowest DIMM for both processors.
RDIMM Ranks population in a three slots per channel configuration

Configuration Number
Max Speed
DIMM2
DIMM1
DIMM0
1
DDR3-1333
-
-
Single-rank
2
DDR3-1333
-
-
Dual-rank
3
DDR3-1066
-
-
Quad-rank
4
DDR3-1066
-
Single-rank
Single-rank
5
DDR3-1066
-
Single-rank
Dual-rank
6
DDR3-1066
-
Dual-rank
Single-rank
7
DDR3-1066
-
Dual-rank
Dual-rank
8
DDR3-800
-
Single-rank
Quad-rank
9
DDR3-800
-
Dual-rank
Quad-rank
10
DDR3-800
-
Quad-rank
Quad-rank
11
DDR3-800
Single-rank
Single-rank
Single-rank
12
DDR3-800
Single-rank
Single-rank
Dual-rank
13
DDR3-800
Single-rank
Dual-rank
Single-rank
14
DDR3-800
Dual-rank
Single-rank
Single-rank
15
DDR3-800
Single-rank
Dual-rank
Dual-rank
16
DDR3-800
Dual-rank
Single-rank
Dual-rank
17
DDR3-800
Dual-rank
Dual-rank
Single-rank
18
DDR3-800
Dual-rank
Dual-rank
Dual-rank
 Table 3:  DIMM RANKS Population in 3 slots per channel
This concludes all the basic elements we need for configuring the perfect server.

-Nir

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