What is a DUAL Mode in RAM.

[valtea]

i see in some mobo specs about singel mode dualmode RAM. What actually is it. Is the clock spead doubled in dual mode?

[bharathbala2003]

single is SDRAM and double is DDR.. thats the simplest.. if u wanna go into lille detail ddr is er.. kinda latest that is used in most of the latest comps as its more efficient..

this i got from wikipedia..

DDR SDRAM or double-data-rate synchronous dynamic random access memory is a type of memory integrated circuit used in computers. It achieves greater bandwidth than ordinary SDRAM by transferring data on both the rising and falling edges of the clock signal (double pumped). This effectively nearly doubles the transfer rate without increasing the frequency of the front side bus. Thus a 100 MHz DDR system has an effective clock rate of 200MHz when compared to equivalent SDR SDRAM, the "SDR" being a retroactive designation.

With data being transferred 8 bytes at a time DDR RAM gives a transfer rate of (memory bus clock rate) * 2 (for dual rate) * 8 (number of bytes transferred). Thus with a bus frequency of 100 MHz, DDR-SDRAM gives a max transfer rate of 1600 MB/s.

[pimpom]

While DDR does stand for Double Data Rate and works as outlined by bharathbala2003, what is usually meant by Dual Mode is different.

Some motherboard chipsets can operate in such a way that when you have two DDR RAM sticks in two separate slots, they work together as a pair at a higher bandwidth in addition to increasing the amount of RAM.

So if your motherboard supports dual-channel mode, your system will be faster if you have, say, two 256MB modules instead of a single 512MB module. The level of overall increase in performance can be expected to be of the order of a few per cent.

Some Athlon XP motherboards such as those with nForce 2 chipsets support dual mode. Socket 754 A64 systems do not support it.