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HP Compaq dc7900 Ultra Slim Desktop PC - Memory Upgrade


The computer comes with DDR 2 synchronous dynamic random access memories (DDR2- SDRAM) small outline dual inline memory modules (SODIMMs).

Supported types are non-ECC PC2-5300 and PC2-6400 DDR2 memory. Supports a maximum memory of up to 8 GB.



The memory sockets on the system board can be populated with up to two industry-standard SODIMMs. These memory sockets are populated with at least one reinstalled SODIMM. Maximum memory support can be achieve by populating up to 8-GB of memory on the system board.


For proper system operation, the SODIMMs must be:
● Industry-standard 200-pin.
● Un-buffered PC2-6400 800 MHz-compliant.
● 1.8 volt DDR2-SDRAM SODIMMs.

The DDR2-SDRAM SODIMMs must also:
● Support CAS latency 5 DDR2 800 MHz (5-5-5 timing) and CAS latency 6 DDR2 800 MHz (6-6-6 timing).
● Contain the mandatory Joint Electronic Device Engineering Council (JEDEC) specification.

In addition, the computer supports:
● 512-Mbit and 1-Gbit non-ECC memory technologies.
● Single-sided and double-sided SODIMMS.
● SODIMMs constructed with x8 and x16 devices; SODIMMs constructed with x4 SDRAM are not supported.

NOTE: The system will not operate properly if unsupported SODIMMs are installed .

Populating SODIMM Sockets

There are two SODIMM sockets on the system board, with one socket per channel. The sockets are labeled DIMM1 and DIMM3. The DIMM1 socket operates in memory channel A. The DIMM3 socket operates in memory channel B.

SODIMM Socket Locations
Socket Color
SODIMM1 socket, Channel A
SODIMM3 socket, Channel B

NOTE: A SODIMM must occupy the black DIMM1 socket. Otherwise, the system will display a POST error message indicating that a memory module must be installed in the black socket.

The system will automatically operate in single channel mode, dual channel mode, or flex mode, depending on how the SODIMMs are installed.

● System will operate in single channel mode if the SODIMM sockets are populated in one channel only.

● System will operate in a higher-performing dual channel mode if the memory capacity of the SODIMM in Channel A is equal to the memory capacity of the SODIMM in Channel B.

● System will operate in flex mode if the memory capacity of the SODIMM in Channel A is not equal to the memory capacity of the SODIMM in Channel B. In flex mode, the channel populated with the least amount of memory describes the total amount of memory assigned to dual channel and the remainder is assigned to single channel. If one channel will have more memory than the other, the larger amount should be assigned to channel A.

● In any mode, the maximum operational speed is determined by the slowest SODIMM in the system.

Memory Socket Loading
Socket 1
Socket 2
1 GB
1 GB
1 GB
1 GB
1 GB
2 GB
2 GB
2 GB
2 GB
4 GB
4 GB
4 GB
4 GB
4 GB
8 GB

NOTE: The previous table does NOT list all possible configurations.

HP recommends using symmetrical loading (same-capacity, same-speed modules across both channels) to achieve the best performance.

NOTE: Each socket can support only up to a maximum of 4 GB.

Memory amounts over 3 GB may not be fully accessible with 32-bit operating systems due to system resource requirements. Addressing memory above 4 GB requires a 64-bit operating system.

Please contact HP PartSurfer to purchase compatible memory from HP.
Click here to go to HP PartSurfer website.

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