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What is SDRAM?

David White
David White

SDRAM stands for Synchronous Dynamic Random Access Memory, and it is a fast method of delivering computing capacity. It can run at 133 Mhz, which is much faster than earlier RAM technologies.

This type of memory is very protective of its data bits, storing them each in a separate capacitor. The benefit of this is that it avoids corruption and maintains "pristine" data. The drawback is that those same capacitors that are so useful at storing the SDRAM bits also happen to be very bad at keeping electrons in check; the result is where the Dynamic part of the name comes in, as refreshes are required to maintain data integrity. Once all of that dynamic refreshing and storing is done with, the result is a dense package of data, one of the densest in the business world.

SDRAM chips can accept more than one write command at a time.
SDRAM chips can accept more than one write command at a time.

The Synchronous part of the name is added with a subroutine that lines itself up with the computer system bus and processor, so that all operations take place at the same time. Specifically, the computer's internal clock drives the entire mechanism. Once the clock sends out a signal saying that another unit of time has passed, the memory chips go to work. In addition to the dense data package of DRAM, it allows a more complex memory pattern, resulting in an extremely powerful method of storing and accessing data.

A stick of DDR-SDRAM, a type of memory.
A stick of DDR-SDRAM, a type of memory.

Another benefit of SDRAM is what is called pipelining. Because the chips are so dense and complex, they can accept more than one write command at a time. This means that a chip can be processing one command while it accepts another one, even if that new command has to wait its turn in the pipeline. Previous RAM chips required proprietary access, allowing only one command at a time throughout the chip. In this way, the chips are faster than their predecessors.

This mostly describes single-data chips, or SDR SDRAM. An even newer kind of chip is double-data-rate, or DDR SDRAM. This allows for even greater bandwidth by making pipeline data transfers twice for every unit of time put forth by the computer's internal clock. One transfer takes place at the beginning of the new unit of time, and the other takes place at the end.

SDRAM chips first came to the computing forefront in 1997. In just three years, they had become the dominant force in memory chips across the computing spectrum.

Discussion Comments

anon359698

What is logical memory?

anon195243

what about DDR3?

anon65999

what is the difference between ddr1 and ddr2?

Tryder

I purchased DDR Ram not to long ago and also realized that I to, have both DDR & SDR slots on my motherboard. On one of my P.C. guides it states that they can not be used simultaneously.

So what am I to do if I want to install more memory onto my computer? I would like to install another DDR but, it only seems to have one slot for DDR. It has more slots but the DDR Ram does not fit into the other slots. So obviously it's for SDRAM or whatever.

Anyone know what to do in this type of situation? Please do help! I'm looking to purchase some tomorrow, so help is needed very soon. Thank You!

josles21

My motherboard has both DDR & SDR slots, so why won't they work together to increase ram? Or should I ask what did I do wrong this time? lol

anon17383

the answer was very straight and understandable.

page is very valuable and easy to understand it.

anon12701

Modern processor caches use SRAM.

djfryoux

What does cache memory use? WRAM, SRAM, DRAM, or EDO?

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    • SDRAM chips can accept more than one write command at a time.
      By: il-fede
      SDRAM chips can accept more than one write command at a time.
    • A stick of DDR-SDRAM, a type of memory.
      A stick of DDR-SDRAM, a type of memory.