Frequently Asked Questions: Rambus RDRAM

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Q: Does my motherboard support RDRAM memory?

A: To benefit from the higher data rates of 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 SDRAM memory cannot be upgrade to RDRAM memory.

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

A: 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. Please check with your motherboard vendor for detailed information.

For best performance, it is recommended that the largest modules be placed in the first pair of slots nearest the memory controller - i.e. if you have a pair of 512MB modules and a pair of 128MB modules, it's best to put the 512MB modules in the first slot.

Q: If I have a Dual Channel Rambus system, can I only purchase one RIMM module to upgrade my system?

A: 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 case you must upgrade each channel equally. 32bit RIMM modules, such as RIMM 4200, 4800, 6400 modules can be upgraded singly on dual channel systems.

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

A: Most systems allows 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.

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

A: 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 system disables the ECC function.

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

A:You can mix speed grades of RIMMS 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.

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

A: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.

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

A: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 users guide.

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

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

Q: What are the common motherboards with RDRAM technology?

A:Common motherboards that support RDRAM memory include: Abit SI7, Asus P4T533, Asus P4T533C, Asus P4TE, Epox EP-4T2A3/4/+, Gigabyte GA-81HXP, 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.

Chipsets that do not support RDRAM technology include Intel D845/865/875, SiS 645/648,/650, 655, Via P4X266/333/400

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

A: 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).

Q: What are available RDRAM frequencies and RIMM module configurations.

A: Current mainstream RDRAM frequency is 1200MHz, available today. RDRAM components are available in 800, 1066, 1200MHz with roadmap to 1333 and 1600MHz. The mainstream RIMM module configuration is RIMM 4800 (32-bits) which incorporate two separate 1200MHz RDRAM channels into a single module. RIMM modules are available in capacities of 64MByte to , and are also available in 16-bit configurations which incorporate a single RDRAM channel per module.

Q: What is the difference between RDRAM™, DDR, and SDRAM memories.

A:RDRAM is used in the highest-performance PC systems. RDRAM memory operates at high-frequency for increased throughput from each component. Current mainstream RDRAM memory operates at transfer speeds of 1200MHz. DDR is targeted towards mainstream applications and typically operate at transfer speeds of 400MHz, and SDRAM is used in low-performance systems and operate at transfer speeds of 133MHz.

RDRAM is performance memory for users seeking to the highest performance from their PC RDRAM-enabled PCs excel at graphics, multimedia, CAD, content creation, and office applications.

Q: Would my applications benefit from RDRAM?

A:RDRAM-enabled computers offers the highest performance in graphics, multimedia, gaming CAD, content creation applications.

Q: Which is the difference in memory bandwidth of RDRAM, DDR, SDRAM?

A:On memory bandwidth: 1200MHz RIMM modules delivers 4.8 Gbyte per second
DDR400 modules: 3.2Gbyte per second
SDRAM PC133 modules: 1.1 Gbyte per second

Q: How long have these memories been around?

A: RDRAM has been shipping in volume in PCs since 1999. DDR has been shipping in volume in PCs since 2000. SDRAM PC133 has been shipping in volume in PCs since 1998.