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DDR2 RAM vs. DDR3 RAM

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October 27, 2009 7:30:24 PM

So I've heard that DDR3 is slower than DDR2 from what something sub mesa said:

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DDR3 has higher latencies than DDR2, DDR2 has higher latencies than DDR1.

This is offset by the higher throughput, as DDR has 2 operations per cycle, DDR2 has 4 operations per cycle and DDR3 has 8 operations per cycle.

So DDR3/800 is actually running 100MHz, DDR2/400 is running 100MHz, DDR/200 is running 100MHz and SDR/100 is running 100MHz. That's why MHz is not used in this context, but MT/s or GT/s; hence DDR3/800 where 800 is the number of transfers per second, not clockcycles.

In short, DDR3 needs to have a clear advantage in GT/s before it can 'overcome' the penalty of higher latencies. It has a 'break-even point' where performance is about the same, and where it starts becoming faster. Generally, you will never notice the difference. But you might notice the difference in quanity of RAM, because it can reduce the need for disk I/O which you do notice.

Just don't get yourself dragged in all the marketing and things the companies want you to believe in. Besides RAM is the least important component to consider for overall systems performance. Even a 100% increase in memory throughput will only yield about 5%-10% of overall systems performance increase. That's nothing compared to the 30000% increase in IOps performance when considering SSD versus HDD, which translates to about 1000% increase in overall systems performance in disk-bound workloads.

http://images.tweaktown.com/content/1/7/1782_3.gif

graph says all; though ofcourse there is faster DDR3 memory. But IMO not worth the money. One good argument for DDR3 is that its getting cheaper than DDR2 in the (near) future, so if you bought to few RAM today you can upgrade DDR3 for less money in the future than DDR2, which will become very expensive because of low production volumes, like DDR1 is today.

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So... is that correct in this case? Which RAM should I get?

4GB DDR3 1600
http://www.newegg.ca/Product/Product.aspx?Item=N82E1682...

or

4GB DDR2 800
http://www.newegg.ca/Product/Product.aspx?Item=N82E1682...

or should I get two sets of these?

2GB DDR2 800
http://www.newegg.ca/Product/Product.aspx?Item=N82E1682...



Thanks in advance for the help. And just to let you know, I have absolutely know experience in overclocking (although I'm nowhere near techshy so I could learn)

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October 27, 2009 8:22:01 PM

shortstuff_mt said:
Well, that makes your decision easy. That motherboard only supports DDR2 RAM. You have to get a motherboard that supports DDR3 RAM if that's what you want to use. I would go the AM3/DDR3 route if it was me. Here's a motherboard for the same price that supports DDR3 RAM:

GIGABYTE GA-MA785GMT-UD2H AM3 AMD 785G HDMI Micro ATX AMD Motherboard - Retail


Ya I saw that, I don't really like how it's microATX though. No real reason, just bugs me. But maybe that'll be the one I'll get. thanks
October 27, 2009 8:31:27 PM

shortstuff_mt said:
Do you need the onboard graphics, or are you adding a GPU? If you don't need the onboard GPU then I would get this CPU + motherboard combo:

Phenom II X3 720 + Gigabyte GA-MA770T-UD3P combo

Here's some nice CAS 7 DDR3 1333 RAM to pair up with the above combo:

G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666) Desktop Memory Model F3-10666CL7D-4GBRH - Retail $93.99


Thanks that combo looks perfect! But the memory, does it make a difference that it's designed for core i7?
a b } Memory
October 27, 2009 8:32:57 PM

Nope, it will work just fine in the motherboard linked above. They just advertise it as being designed for the i5/i7 since it runs at 1.5v. Anything above 1.65v can damage the i5/i7 chips.
October 27, 2009 8:52:57 PM

Well, the difference is not that important anymore. Also, DDR3 will eventually replace DDr2.
!