The memory architecture featured in the Dell PowerEdge 1850 is DDR2 PC3200 240-pin SDRAM memory. The memory is also registered, error-checking and correction (ECC), 72-bits wide and operates at 400-MHz, regardless of host bus speed.

Single and Dual Rank DIMMs

Determining if a DIMM is a single-rank DIMM or a dual-rank DIMM is difficult upon visual inspection. A single-rank DIMM may have memory chips on both sides of a DIMM. The best way to decide if the DIMM is a single-rank DIMM or a dual-rank DIMM is to look at its attached label. The following image contains the labeling convention used to determine the exact specifications of the DIMM.

This picture shows the DIMM naming convention.

NOTE: In this example, 2R represents a dual-rank DIMM.

Error Checking and Correcting

Error Checking and Correcting (ECC) is remains the standard technology for basic data resiliency. ECC memory uses registered DIMMs and all error correction occurs at the memory controller.

Spare Bank

Bank 3 can be used as a spare bank of memory in the event of a DIMM failure in bank 1 or 2. Memory bank 3 acts as a failover bank and is only active in the event of a failover. All DIMMs must be the same size and rank type for the spare bank failover to work effectively. Total system memory size will be the reported memory amounts for banks 1 and 2. This feature can be enabled or disabled in the BIOS.

Memory Mirroring

The Dell PowerEdge 1850 supports Memory Mirroring that enables the second bank of memory DIMMs to mirror (similar to RAID-1) the active memory bank. This memory is not hot-swappable, but does allow the server to continue operating in the event of a DIMM failure. Only banks 1 and 2 are active in the mirroring of data. This feature can be enabled or disabled in the BIOS.

Chipfail

Chipfail technology detects multi-bit memory errors and then rewrites the data from the failing memory chip to a different chip. The failing chip is then disabled. This does not affect the total size of memory available for the DIMM.

Memory Configurations

The system can operate with only one DIMM installed. If more than one DIMM is used, the memory bank must be filled with the same type of memory. For example, when two 256MB DIMMs are installed in Bank 1, both DIMMs must be either singe-rank DIMMs or both must be dual-rank DIMMs.

Use the following table to determine the correct DIMM configurations.

Memory Configurations
Total Memory	Single or Dual-Rank DIMMs Bank 1		Single or Dual-Rank DIMMs Bank 2		Single-Rank DIMMs ONLY Bank 3
Total Memory	DIMM_1	DIMM_2	DIMM_3	DIMM_4	DIMM_5	DIMM_6
256MB	256MB	EMPTY	EMPTY	EMPTY	EMPTY	EMPTY
512MB	256MB	256MB	EMPTY	EMPTY	EMPTY	EMPTY
1GB	256MB	256MB	256MB	256MB	EMPTY	EMPTY
1GB	512MB	512MB	EMPTY	EMPTY	EMPTY	EMPTY
2GB	512MB	512MB	512MB	512MB	EMPTY	EMPTY
2GB	1GB	1GB	EMPTY	EMPTY	EMPTY	EMPTY
3GB	1GB	1GB	512MB	512MB	EMPTY	EMPTY
3GB	512MB	512MB	512MB	512MB	512MB	512MB
4GB	1GB	1GB	1GB	1GB	EMPTY	EMPTY
4GB	1GB	1GB	512MB	512MB	512MB	512MB
6GB	2GB	2GB	1GB	1GB	EMPTY	EMPTY
6GB	1GB	1GB	1GB	1GB	1GB	1GB
8GB	2GB	2GB	2GB	2GB	EMPTY	EMPTY
8GB	2GB	2GB	1GB	1GB	1GB	1GB
12GB	2GB	2GB	2GB	2GB	2GB	2GB
16GB	4GB	4GB	4GB	4GB	EMPTY	EMPTY

This is an image of the Memory Banks