Memory Organization And Operating Modes; Single-Channel Mode; Dual Channel Modes; Dual Channel Symmetric Mode - Intel X38 Configuration Manual

4 Memory Organization and
Operating Modes
The Intel X38 Express Chipset memory interface is designed with Intel
Technology so that it can be can be configured to support single-channel or dual-
channel DDR2 or DDR3 memory configurations. Depending upon how the DIMMs are
populated in each memory channel, a number of different configurations can exist for
DDR2 or DDR3.
The following sections explain and show the different memory configurations that are
supported by the X38 Express Chipset.
4.1

Single-Channel Mode

In this mode, all memory cycles are directed to a single channel.
Single channel mode is used when either Channel-0 or Channel-1 DIMMs are
populated in any order, but not both.
4.2

Dual Channel Modes

4.2.1

Dual Channel Symmetric Mode

This mode provides maximum performance on real applications. Addresses are ping-
ponged between the channels after each cache line (64 byte boundary). If there are
two requests, and the second request is to an address on the opposite channel from
the first, that request can be sent before data from the first request has returned. If
two consecutive cache lines are requested, both may be retrieved simultaneously,
since they are ensured to be on opposite channels.
Dual channel symmetric mode is used when both Channel-0 and Channel-1 DIMMs are
populated in any order with the total amount of memory in each channel being the
same, but the DRAM device technology and width may vary from one channel to the
other.
Table 4-1 is a sample dual channel symmetric memory configuration showing the rank
organization.
12

Memory Organization and Operating Modes

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