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At Rambus, we create cutting-edge semiconductor and IP products, spanning memory and interfaces to security, smart sensors and lighting.

RDRAM Memory Architecture

RDRAM®, Rambus’ first mainstream memory architecture, has been implemented in hundreds of millions of consumer, computing and networking productsfrom leading electronics companies including Cisco, Dell, Hitachi, HP, Intel, Panasonic, SiS, Sony, Texas Instruments, and Toshiba.

For general information about RDRAM components and RIMM modules, see the FAQ below.

Rambus RDRAM FAQ

Can I buy memory directly from Rambus?

No, Rambus licenses RDRAM technology to manufacturing partners, but does not sell components or modules.

Does my motherboard support RDRAM memory?

To support RDRAM memory, your motherboard must incorporate a chipset specifically designed to support RDRAM memory or RIMM modules. RDRAM-enabled chipsets include: SiS R659 (4-channels), SiS R658 (dual channels), Intel 850E, 850, 960, 840 (dual channels), Intel 820. Motherboards with DDR or SD DRAM memory cannot be upgraded to RDRAM memory.

Where can I buy RIMM modules to upgrade my systems?

Before purchasing, note whether your system takes 16 bit or 32 bit RIMM modules. For a list of retailers, please search Google using “RDRAM”.

Do I need to upgrade the memory modules in my PC systems in pairs?

Before purchasing, note whether your system takes 16 bit or 32 bit RIMM modules, and whether your computer is a dual-channel or 4-channel system. For 4-channel RDRAM chipsets and motherboards, memory module upgrades should be in matched pairs. For instance, to add 512MByte of memory into a dual or 4-channel system, two matched 256MByte modules should be inserted.

For dual-channel RDRAM chipsets and motherboards, memory module upgrades should be in matched pairs. Please look at your PC or motherboard user manual for details.

If I have a Dual-channel Rambus system, can I only purchase one RIMM module to upgrade my system?

Before purchasing, note whether your system takes 16 bit or 32 bit RIMM modules. Please check with your motherboard vendor for detailed information. In most cases, you must upgrade each channel equally. 32bit RIMM modules, such as RIMM 4200, 4800, 6400 modules can be upgraded singly on dual-channel systems.

Can I mix RIMM modules from different manufacturers into my system?

Most systems allow mixed RIMM modules from different manufacturers. Note that the chipset should be rated to handle the frequency and memory core of the upgrade modules. You may have to verify that the system BIOS or motherboard supports the desired memory density.

Can I mix RIMM modules of different frequencies, or ECC/non-ECC into my system?

When mixing module frequency or error-correction code (ECC), most RDRAM systems will default to lowest frequency among the inserted modules. In addition, if any of the modules do not support ECC, then most systems disable the ECC function.

Can I install a PC800 RIMM in my system that already has a PC1066 RIMM module installed?

You can mix speed grades of RIMM’s in most systems. However the system will run at the lowest speed grade of RIMM module installed. So for this instance your memory sub system would only run at 800 Mhz.

Can I mix RIMM modules with different memory bit densities in the same system?

When mixing module frequency or error-correction code (ECC), most RDRAM systems will default to lowest frequency among the inserted modules. In addition, if any of the modules do not support ECC, then the system will usually disable the ECC function. Refer to the adding in pairs answer above.

Can I use 16-bit and 32-bit RIMM modules in the same systems?

No, currently available motherboards support either 16-bit or 32-bit RIMM modules, not both. Be sure to select the appropriate module or consult your motherboard/system user manual.

I have a RDRAM-enabled PC or motherboard with 800MHz RDRAM. Can I upgrade to 1066MHz or 1200MHz?

Usually not. Whereas most systems can support slower RDRAM frequencies, systems are not guaranteed to support faster RDRAM frequencies. Please consult your PC or motherboard user manual or manufacturer for details.

What are the common motherboards with RDRAM technology?

Common motherboards that support RDRAM memory include: Abit SI7, Asus P4T533, Asus P4T533C, Asus P4TE, Epox EP-4T2A3/4/+, Gigabyte GA-8IHXP, Intel 850EMV2, Intel 850GB, , IWILL P4R533N, IWILL PX400-SN, MSI 850Emax2.

Popular systems that support RDRAM memory include: Dell Dimension 8100/8200/8250, XPS B866, Gateway XL700, Alienware Area-51 with Intel 850E chipset, Falcon NW Mach V with Intel 850E chipset, etc.

What is the difference between 184pin, 168pin, 242pin RIMM modules?

The number of pins on a RIMM module determines the number of RDRAM channels supported per module. Single channel modules come in 168 or 184 pin configurations and both types of modules are interchangeable in most systems. Dual-channel modules use the 242 pin configurations, providing 2 independent channels per module. These are configured as RIMM 4200 (1066MHz operation), RIMM 4800 (1200MHz operation), or RIMM 6400 (1600MHz operation).

What are available RDRAM frequencies and RIMM module configurations?

RDRAM components are available in 800, 1066, and 1200MHz. The mainstream RIMM module configuration is RIMM 4800 (32-bits) which incorporates two separate 1200MHz RDRAM channels into a single module. RIMM modules are available in capacities of 64MByte, and are also available in 16-bit configurations which incorporates a single RDRAM channel per module.

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