RAM frequency confusion

cyberfish · May 24, 2008

Hi,
I haven't bought a new computer for a while (since the beginning of DDR2 era), and am throughly confused by frequency markings.

Are DDR2 memory sticks only double rated like DDR?

That is to say, can I run DDR2 800MHz PC2-6400 ram at 400 (1600) FSB? (within spec)

Thanks

Blazing fire · May 24, 2008

Well, I'm not sure what you mean by "double rated like ddr" but a PC2-6400 is actually running at 400mhz and X2. And X2 again if you're running dual channel. Dual channel is running 2 modules stimuinatiously to double the speed. All these "X2" are like quad-pumped intel CPUs, meaning the total effective bandwidth.

cyberfish · May 24, 2008

Thanks for the reply.

By "double rated" I mean "effective frequency". Nothing to do with dual channel. (The "double" in "double data rate (DDR)")

For example, DDR-400 actually runs at 200. (But since it can do twice as much per clock as SDR RAM, it is marketted as DDR-400, so computer illiterates won't think it's slower than, eg, SDR-300).

cyberfish · May 24, 2008

Wikipedia cleared it up for me.
http://en.wikipedia.org/wiki/DDR2_SDRAM#Specification_standards

Seems like DDR2 is quad-pumped, unlike DDR, which is only doubled.
That is to say, DDR2-800 is the same as DDR-400 in terms of FSB.
(DDR2-800 supports up to FSB 200, DDR-400 also supports up to FSB 200)

crosshairs · May 24, 2008

cyberfish said:
(DDR2-800 supports up to FSB 200, DDR-400 also supports up to FSB 200)

not quite....DDR2 is not quad pumped...DDR2-800 (PC6400) will do 400Mhz FSB..not 200

Randyman... · May 25, 2008

Yep. DDR800 = 400FSB. The "Double Data Rate" means you are transerring Data on the Peak (Hi) AND Trough (Low) of each clock cycle instead of just the Peak of the clock cycle. This effectively doubles the amount of work/bandwidth per clock cycle

I believe DDR3 follows suit here as well...

cyberfish · May 25, 2008

Thanks for the corrections!

Upon further research, that is indeed the case (DDR2 is only doubled just like DDR).

So I guess I don't need anything higher than 800 unless I want to overclock above FSB 400 =).

Blazing fire · May 25, 2008

What CPU are you using? If you're going to use a multi at 9, you will only get 3.6ghz. Btw, you know what overclocking is right?

crosshairs · May 25, 2008

Blazing fire said:
What CPU are you using? If you're going to use a multi at 9, you will only get 3.6ghz.

Not necessarily true... My Patriot PC6400 runs easily at 900 MHz with 2.2v and 4-4-4-15 timings..I have had it at 1000 5-5-5-16, but I prefer the lower timings over higher clockspeed for that rig.

Blazing fire said:
Btw, you know what overclocking is right?

yeah, do you...?

Just like 2.4 is stock for a Q6600, 800 is stock for PC6400....that in no way means thats all it will run at, thats just what it is spec'd for...Ram overclocks just like CPU's do..

cyberfish · May 25, 2008

Yeap, I know what overclocking is.

E6300 =) multiplier 7. On a tight budget here.

That would be 2.8GHz assuming the RAM (OCZ gold DDR2-800 2x1GB kit) cannot overclock at all (or I can just run it out of sync with FSB).

Blazing fire · May 25, 2008

crosshairs said:
Not necessarily true... My Patriot PC6400 runs easily at 900 MHz with 2.2v and 4-4-4-15 timings..I have had it at 1000 5-5-5-16, but I prefer the lower timings over higher clockspeed for that rig.

yeah, do you...?

Just like 2.4 is stock for a Q6600, 800 is stock for PC6400....that in no way means thats all it will run at, thats just what it is spec'd for...Ram overclocks just like CPU's do..

He says he will not go above 400mhz.

Anyway, if you're on a budget and using an E6300, why buy such a good RAM? I use kingston value RAM ($29 for 1 1GB stick X2) and it hits like 960mhz, 5-5-5-15, memtest+ stable.

Frankly, I doubt you will see a noticable diff between 3-3-3-9 1T over 5-5-5-15 2T in terms of FPS. Benchmark is another story though.

Edit: There are other "sub timings", more advance ones to max the RAM out.

hank123 · May 25, 2008

Blazing fire said:
Frankly, I doubt you will see a noticable diff between 3-3-3-9 1T over 5-5-5-15 2T in terms of FPS. Benchmark is another story though.

meh. Im not sure but this may to imply to intel as a hole with the memory bandwidth thing and the T1 vers T2.

I know AMD still slower clock for clock how ever eats intel on the memory bandwidth.

cyberfish · May 25, 2008

Anyway, if you're on a budget and using an E6300, why buy such a good RAM? I use kingston value RAM ($29 for 1 1GB stick X2) and it hits like 960mhz, 5-5-5-15, memtest+ stable.

Because it's on sale where I live, and I can get it for $30CDN (~=$30 USD) =).
http://a-power.com/product-2461-301-bestseller

Lucky I know =).

Blazing fire · May 26, 2008

hank123 said:
meh. Im not sure but this may to imply to intel as a hole with the memory bandwidth thing and the T1 vers T2.

I know AMD still slower clock for clock how ever eats intel on the memory bandwidth.

err ok

cyberfish said:
Because it's on sale where I live, and I can get it for $30CDN (~=$30 USD) =).
http://a-power.com/product-2461-301-bestseller

Lucky I know =).

That's good! Good luck in ocing!

aoch88 · May 26, 2008

This would mean PC8500 (DDR2-1066) is guaranteed 533FSB?

crosshairs · May 26, 2008

aoch88 said:
This would mean PC8500 (DDR2-1066) is guaranteed 533FSB?

Theoretically yes....But there have been modules that wont run rated speed.....I had a set that wouldn't...RMA'd them and the replacement set was fine.

aoch88 · May 26, 2008

Thanks but if it doesn't do that rated speed at default voltage it means the part is faulty because it says DDR-1066. I believe a replacement is valid. Thanks for the confirmation - wanted to get the PC8500

Blazing fire · May 26, 2008

DDR-1066? Where?

Yup, it MUST run at the rated speed. Don't ever, ever accept one that does not. Just RMA a thousand times if you have to.

RAM frequency confusion

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