A useful guide to buying RDRAM otherwise known as Rambus, RIMM or DRAM
RDRAM or Rambus Dynamic Random Access Memory
Most commonly used in late Pentium 3 and early Pentium 4 motherboards post 1999, RDRAM offered vast bandwidth improvements over SDRAM and early DDR memory as it was truly dual channel. This meant it could run at speeds of up to 1066Mhz and bandwidth of up to 6400 mega bits per second.
RDRAM Bandwidth Table
- PC600: 16-bit, specified to operate at 300 MHz clock speed, 1200 MB/s bandwidth
- PC700: 16-bit, specified to operate at 355 MHz clock speed, 1420 MB/s bandwidth
- PC800: 16-bit, specified to operate at 400 MHz clock speed, 1600 MB/s bandwidth
- PC1066 (RIMM 2100): 16-bit, specified to operate at 533 MHz clock speed, 2133 MB/s bandwidth
- PC1200 (RIMM 2400): 16-bit, specified to operate at 600 MHz clock speed, 2400 MB/s bandwidth
- RIMM 3200: 32-bit, specified to operate at 400 MHz clock speed, 3200 MB/s bandwidth
- RIMM 4200: 32-bit, specified to operate at 533 MHz clock speed, 4200 MB/s bandwidth
- RIMM 4800: 32-bit, specified to operate at 600 MHz clock speed, 4800 MB/s bandwidth
- RIMM 6400: 32-bit, specified to operate at 800 MHz clock speed, 6400 MB/s bandwidth
RDRAM Q & A
- Q - Does RDRAM need to be installed in pairs?
- A - As a rule of thumb 16-bit RDRAM must be installed in matched pairs, however some early RIMM motherboards run single channel and allow individual modules. All 32-bit boards allow single modules to be installed.
- Q - Do all RIMM slots need to be filled?
- A - Yes, 16-bit RIMM slots must be filled with either RDRAM modules or blanking modules called CRIMMs
- Q - Do I need 16-bit or 32-bit RDRAM memory?
- A - This depends on your motherboard. You cannot use 16-bit modules in a 32-bit board and vice versa. A list of 16-bit and 32-bit RDRAM motherboards can be viewed from any of My RDRAM auctions.
- Q - What is the difference between 184pin ond 232pin RDRAM?
- A - 184pin is 16-bit and 232pin is 32-bit
- Q - I know I need 16-bit but do I need pc600, pc700, pc800 or pc1066?
- A - This depends on your motherboard. Most Pentium 3 boards use pc600 RDRAM, most Pentium 4 boards require at least pc800. Only 533Mhz clock speed systems need pc1066. ie the Dell Dimension 8250
- Q - What is the difference between pc800-45 and pc800-40?
- A - The -40 or -45 after the pc800 relates to the response timing or latency of the memory. Some 533Mhz systems like the Dell Dimension 8250 will work with the faster response time pc800-40 memory.
- Q - If I install pc800-40 memory instead of pc1066 in my 533Mhz system will it slow it down?
- A - No, it wont slow the system but the memory will only run at 400Mhz per channel not 533Mhz which will make some difference.
- Q - I have a Dell Dimension 8200. Is it 400Mhz or 533Mhz?
- A - Dell in their infinite wisdom made the 8200 in 400Mhz and 533Mhz. The easiest way of telling which you have is to look your processor up on the Intel web site. Search for processor finder via Google.
- Q - What is ECC and can I mix ECC and non-ECC modules?
- A - ECC or Error-Correcting Code is an on device memory utility that checks for memory allocation errors before allocation thus reducing memory errors. Used mainly in servers. RDRAM allows ECC and non-ECC to be mixed but all modules will operate as non-ECC.
- Q - Dell say I must use non-ECC memory but you say either is fine. Who is correct?
- A - Dell stipulate non-ECC as their systems cannot use the ECC function. But ECC modules will operate perfectly as non-ECC modules in non-ECC systems. The ECC function is simply not available in such instances.
- Q - Can I mix different size and manufacturer RDRAM modules?
- A - Which manufacturer doesn't make a difference as long as the modules have a matched configuration. Different size modules must not be used in the same channel but can be used in different channels as long as each channel contains matched pairs.
- Q - What manufacturer is best for RDRAM?
- A - In my experience Kingston made the most reliable RDRAM. Samsung and Infineon are also recommended. Brands that should be avoided include Elpida and NEC.
If you are still in doubt about what RDRAM you require please contact me via the contact member button: Contact Member