Asus M4A78-HTPC/RC - Manual (Page 22)

1.7 System memory
1.7.1 Overview
The motherboard comes with two Double Data Rate 2 (DDR2) Dual Inline Memory Modules
(DIMM) sockets. A DDR2 module has the same physical dimensions as a DDR DIMM but
has a 240-pin footprint compared to the 184-pin DDR DIMM. DDR2 DIMMs are notched
differently to prevent installation on a DDR DIMM socket. The figure illustrates the location of
the DDR2 DIMM sockets:
Channel Sockets
Channel A DIMM_A1 and DIMM_A2
Channel B DIMM_B1 and DIMM_B2
1.7.2 Memory configurations
You may install 512MB, 1GB, 2GB and 4GB unbuffered ECC/non-ECC DDR2 DIMMs into the
DIMM sockets.
• You may install varying memory sizes in Channel A and Channel B. The system maps
the total size of the lower-sized channel for the dual-channel configuration. Any excess
memory from the higher-sized channel is then mapped for single-channel operation.
• Always install DIMMs with the same CAS latency. For optimum compatibility, we
recommend that you obtain memory modules from the same vendor.
• Due to the memory address limitation on 32-bit Windows OS, when you install 4GB
or more memory on the motherboard, the actual usable memory for the OS can be
about 3GB or less. For effective use of memory, we recommend that you install a 64-bit
Windows OS when having 4GB or more memory installed on the motherboard.
• This motherboard does not support DIMMs made up of 256 Mb chips or less. (Memory
chip capacity counts in Megabit, 8 Megabit/Mb=1 Megabyte/MB.)
• The default memory operation frequency is dependent on its SPD. Under the default
state, some memory modules for overclocking may operate at a lower frequency than
the vendor-marked value.
• For system stability, use a more efficient memory cooling system to support a full
memory load (4 DIMMs) or overclocking condition.
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