Which companies build 4 GB of RAM DDR2

Dual channel mode for DDR, DDR2, DDR3 and DDR4

Put simply, a dual channel configuration doubles the theoretical data transfer rate of your system compared to the single channel mode. This is done by bundling a suitable pair of modules in conjunction with parallel memory access to the two memory channels.

In the following we explain the requirements and configurations under which the dual channel mode is possible. First we examine the dual channel mode of the chipsets for DDR1 DRAM such as Intel i865, i875, the Northbridge integrated in the AMD CPU, etc. (dual channel with symmetrical assembly).

In the course of development, the dual channel mode has been improved and the requirements for the memory modules have also been modified. Newer chipsets for DDR2 memory offer expanded options for DDR2, DDR3 and DDR4 systems such as the dual channel (interleaved) mode or the flex mode.

Overview of memory configurations:

Dual channel mode with symmetrical configuration - two or four DIMMs

The dual channel mode is set by the system for the respective memory channel individually activated when you 2 identical DIMMs insert as follows:

Requirements for a dual channel mode

  • Paired distribution of the DIMMs in each of the memory channels (module pair)
  • Identical Module capacity of the module pair (128MB, 256MB, 512MB, 1GB, etc.)
  • Identical DRAM technology of the module pair (128Mb, 256Mb, 512Mb or 1Gb)
  • Identical DRAM bus width of the DRAMs used on the module pair (x8 or x16)
  • Both modules either only single-sided (1 rank) or only dual-sided (2 rank)
  • Mirror-image assembly of the memory slots

Note: Configurations that do not meet these requirements automatically work in single channel mode.
The speed of the bus cycle and the memory access for the entire main memory is determined by the slowest DIMM installed in the system.

The following conditions within a module pair must Not be fulfilled:

  • The same manufacturer of the module or the DRAM components
  • Identical timing, access times, etc.
  • Same speed class of DDR modules (PC2100, PC2700 or PC3200)

Dual Channel (Interleaved) mode

The dual channel (interleaved) mode offers the highest performance. It is activated when the respective Total capacity of the built-in memory modules is identical in both channels is. The speed and DRAM organization of the modules can vary. The speed of the bus cycle and the memory access for the entire main memory is determined by the slowest DIMM installed in the system. It is important that the total capacity in channel A and B is identical. This can be achieved with 2, 3 or 4 DIMMs.

Dual Channel (Interleaved) mode configuration with two DIMMs
Dual Channel (Interleaved) mode configuration with three DIMMs

Dual Channel (Interleaved) mode configuration with four DIMMs
Requirements for a dual channel mode

  • Distribution of the DIMMs to both memory channels
  • Identical total capacity in each memory channel (256MB, 512MB, 1GB, etc.)
  • Mirror-image assembly of the memory slots

Note: Configurations that do not meet these requirements automatically work in single channel mode.

The following conditions within a module pair must Not be fulfilled:

  • The same manufacturer of the module or the DRAM components
  • Identical DRAM technology of the module pair (128Mb, 256Mb, 512Mb or 1Gb)
  • Identical DRAM bus width of the DRAMs used on the module pair (x8 or x16)
  • Both modules either only single-sided (1 rank) or only dual-sided (2 rank)
  • Identical timing, access times, etc.
  • Same speed class of DDR2 modules (PC2-3200, PC2-4300, PC2-5300, etc.)

Note: The speed of the bus cycle and the memory access for the entire main memory is determined by the slowest DIMM installed in the system.

Single Channel (Asymmetric) mode

The single mode is activated when the respective total capacity of the built-in memory modules is different in both channels. The speed of the bus cycle and the memory access for the entire main memory is determined by the slowest DIMM installed in the system.

Single Channel (Asymmetric) mode configuration with one DIMM

Single Channel (Asymmetric) mode configuration with three DIMMs

Dual Channel (Flex Mode)

This new additional technology offers the greatest flexibility when equipping memory modules. It removes, so to speak, almost all previous restrictions and requirements on the memory modules. The dual channel mode also works when only 2, 3 or 4 DIMMs with different total capacities are used in the memory channels.

The largest capacity available in both memory channels is operated in dual channel mode.
In addition, the address area operated in dual channel mode is mapped to the lowest area used first and most frequently by the operating system. The rest of the main memory is operated in single channel mode.

Dual Channel (Flex Mode) configuration with two DIMMs

Requirements for Flex Mode

  • At least one DIMM in each memory channel
  • Mirror-image assembly of the memory slots

The following conditions must Not be fulfilled:

  • The same manufacturer of the module or the DRAM components
  • Identical total capacity in each memory channel (256MB, 512MB, 1GB, etc.)
  • Identical DRAM technology of the module pair (128Mb, 256Mb, 512Mb or 1Gb)
  • Identical DRAM bus width of the DRAMs used on the module pair (x8 or x16)
  • Both modules either only single-sided (1 rank) or only dual-sided (2 rank)
  • Identical timing, access times, etc.
  • Same speed class of DDR2 modules (PC2-3200, PC2-4300, PC2-5300, etc.)

Note: The speed of the bus cycle and the memory access for the entire main memory is determined by the slowest DIMM installed in the system.


© CompuRAM, 2013
01.04.13, Updated on 07/23/19

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Keywords: installation, technology