Any rule of the thumb when comparing DDR3 to DDR2?

I know this might appear to be comparing apples to oranges--if so just let me know. But when shopping for desktops (all with dual-core cpus in the 2.5-3.0 GHz range), I am still seeing DDR2 on sale. I know that eventually it will be phased out and thus be more expensive to upgrade. I'm wondering about comparing RAM in both types--is DDR3 twice as fast as DDR2? Meaning, would 2 gigs of DDR3 be as fast/good as 4 gigs of DDR2?

Or can this comparison not be made? There must be some performance reason why they introduced DDR3. What would the performance boost be for common household computing (surfing, watching youtube videos, etc.)?

 

It's apples and oranges, you cant mix n match so go with the system that you want for the foreseeable future no matter the RAM type, as you say though eventually DDR2 will be more expensive to change.

 

Size is not related to speed. DDR3 should be faster, but testing I have read say it isn't much faster. (You will see the "base" speed rated as MHz, but there are other factors.)

4GB is twice the size of 2GB, be it DDR3, DDR2, DDR or any other.

I agree with future-proofing.

 

Matt is right, DDR3 has twice the bandwidth of DDR2, but that does not necessarily make it twice as fast in actual computer work. There are many more factors involved like the speed of the ram your latency and timings.
But future-proofing wise DDR3 is the way to go.
But when you do you also have to take into consideration the Motherboard you desire and the compatibility of the CPU that you intend to get.
Happy Hunting
hawk22

 

Not really. DDR is better than SDRAM. DDR2 is better than DDR. And DDR3 is better than DDR2. Simple as that.

But it is not just that DDR3 is capable of delivering twice the data rate. DDR3 consumes about 30% less power than DDR2 and they have a maximum capacity of 16Gb per module compared to a theoretical limit of 8Gb for DDR2. I say theoretical because I have never seen DDR2 in sizes larger than 4Gb.

DDR2 is going away. Therefore, if buying a new motherboard that supports DDR2 (though not sure why you would unless on a tight budget and less concerned about future upgrade-ability), I recommend buying a full complement of RAM with the board, and don't plan on upgrading RAM later.

Note too that while both DDR2 and DDR3 look similar, and have the same number of pins, they are NOT compatible and you cannot use DDR2 in a DDR3 motherboard, or DDR3 in a DDR2 motherboard. They are keyed differently and will not fit the slots.

 

A further comment on Bill's post - To scrimp on memory when buying/building a new unit is not cost effective. I help other computer users in a retirement community where I live. I see so many computers where people have been struggling with a "slow" machine for several years and it is simply because whoever "helped" them buy their computer 5 or 6 years ago tried to cut costs by getting a machine with the minimum recommendations.

Sure - it is easy to make a machine appear magical by taking their memory from 256 MB to 1 GB or more but they have been dealing with a maddeningly slow machine for the past two or three years. I helped a lady with a minor computer problem, on a five year old computer, a few days ago and was amazed at the responsiveness. When I looked at the innards, it had 1 GB on a Windows XP Home unit - a belated gift from the friend that helped her buy her computer.

My rule of thumb is to look at the recommendations of the seller and then double it.