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Buying and Installing RIMMs

RDRAM memory is the product of Rambus, a memory designer. It is supported by Intel and designed to work with the Intel Pentium 4 processors. RDRAM is packaged on memory modules called RIMMs (Rambus inline memory modules).

When you read the specifications for RDRAM, you might be amazed at how fast it is compared to other forms of memory. For example, you'll see RDRAM listed as running at 400 MHz and 800 MHz. But RDRAM uses a 16-bit data path compared to the 64-bit data path of SDRAM modules (DIMMs and DDR-DIMMs). That means you need to divide the RDRAM's stated speed by four to compare it with the other memory types. So, an 800 MHz RDRAM is equivalent to 200 MHz DDR memory. There are other issues with RDRAM, including the fact that it is more expensive.

New RDRAM motherboard designs that use the Intel 850 chipset boost RDRAM speed by doubling the data path between the CPU and memory. This is done by pairing chips up to create a 32-bit data path. When installing RDRAM, you must install them in pairs to take advantage of this feature. These systems have four slots to account for the pairing.

Here are some basic rules for RIMMs in HP Pavilion models that support them:

  • RIMM modules must be installed in pairs, and they must be identical (same manufacturer and type). All four RIMM sockets must be filled. If you aren't populating a socket with a RIMM, the empty socket must be filled with a C-RIMM (continuity RIMM). Two C-RIMMs are included on the motherboard.

  • RIMMs must be 184-pin RDR (RDRAM), non-ECC (non-error correction checking), and compliant with the Rambus/Intel specification.

  • The use of Rambus signaling level technology permits 600 to 800 MHz transfer rates. The HP Pavilion models that support RIMMs use PC600 or PC800 RDR modules.

For more information, refer to the following Web pages:

HP Pavilion PCs – Memory Specifications and How to Upgrade RAM: http://www.hp.com/cposupport/personal_computing/support_doc/bph03886.html.

HP Pavilion 1G PC – Rambus Memory Specifications: http://www.hp.com/cposupport/personal_computing/support_doc/bph05598.html.

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