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Synchronizing the FSB and the RAM

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March 21, 2008 1:16:13 AM

Hello everyone;

i am buying a new desktop, but there are still some blurry things in my head, so i will try my best to be clear.

the new E8XX0 cpu cores from intel work with a 1333MHz FSB, and from what i was able to acknowledge, it was meant to work with DDR3-1333 for maximum performance.

since i won't be using DDR3 memories (i find them too expensive still), by using PC2-5300 (DDR2-667) memories, supposedly the best and more adequate for a FSB of 1333 (for synchronization reasons), am I not losing in global performance (CPU+MEM) when compared with a E6X00 CPU with a 1066 FSB that allows faster (or so I believe) PC2-8500 (DDR-1066) memories?

In other words, for those using DDR2 over DDR3 (and has no intentions of upgrading it in the near future), what is preferable? an E8XX0 (FSB 1333) or an E6X00 (FSB 1066)?

Core 2 Duo E6700 : FSB 1066 : 2667Mhz
Core 2 Duo E8200 : FSB 1333 : 2667Mhz

can i use memories over DDR2-667 on a E8XX0 CPU? i presume they'd lose synch, but how bad is it? does it perform properly? Is it safe? does it require any special configuration or can i just insert them as i would with synch mems?

Please bare in mind that i will be doing no OC of any sort in any component.


Thank you!

More about : synchronizing fsb ram

March 21, 2008 1:43:35 AM

There must be 100s of posts exactly like this, use the search tool from now on :non: 

Anyway, for a 1333FSB, your base clock is 333. Now, DDR (Double Data Rate) RAM runs at 2x the base clock (333). 667 IS the optimal speed for your processor. Same goes for 1066FSB; you should use 533Mhz RAM.
March 21, 2008 1:48:42 AM

i would use the search, but anything i try, i get

"Your search must be three characters long at least "
Related resources
March 21, 2008 8:18:44 AM

:D  Ya, I think the search engine is faulty ...

Anyway, I will try to put it short:

actually you could use any DDR2 speed for any latest Intel processors. But you'll be better with RAM with 1:1 ratio (like monst0r said) or a step higher. Like monst0r said: for FSB1333 processor, to get an optimal speed for your RAM, you should get DDR2-667. But you can also use DDR2-800. IMO, better get DDR2-800 for an FSB 1333 processor. I know someone will start arguing my statement. But from my personal experience DDR2-800 on FSB1333 is working just fine, even slightly better than DDR2-667 IMO.
a b V Motherboard
March 21, 2008 11:10:54 AM

Antas and Monst0r are right.

For your RAM and FSB to be 1 to 1 with most of those, you would need DDR2 667. If you get DDR2 800, you could get a moderate overclock and still be 1 to 1.

I have the E6750 (8 x 333MHz = 2.66 GHz), so my DDR2 800 gives me a little room to overclock, which I plan to do soon.
March 21, 2008 11:16:55 AM

True... get 800Mhz if you can.
a b V Motherboard
March 21, 2008 11:40:09 AM

The E8XX0 is based on 45 nm process. Will stay cooler and use less electricity. Your chances of overclocking well are higher if you choose.
DDR3 is preferable on very high overclocks. Still pretty expensive AFAIK.
You can buy DDR2-800 and adjust it to a lower speed and tighten up the timings. The benefit there is mostly the better timings. The price difference between DDR2-667 and DDR2-800 is not much. I always buy one step up from the minimum speed.
March 21, 2008 12:35:54 PM

Hi Underclock
You are right in your question
Now it is not an easy task as it was 4-5 years ago where it was enough to select your Mobo ans and install the compatible Ram ( QVL ) and processor, insert Graphic card and here you go
In your case all memories starting from 667 up-to 1333 will work and you can ckeck in QVL of your Mobo
But as long as you are going to OC everything will be messed up . You have to decide first your Mobo and then Processor and then decide how far youare going to OC and then your real work will start to select your ram which will give you the best results after OC .You have to make lot of research and I advise you to ckeck the Asus Rampage Formula in anandteck, it is amazing and I was really surprized that such subject is not available in Toms
It is not at all as easy as saying 1:1
Though 1:1 is basically correct but when you start playing with clock speed ,core voltage ,ram voltage and multiplier everything will change and the rule of 1:1 is not valid anymore
Again go and ckeck that review in anandtech
I do not know if it is allowed to the link here otherwise I would have done it
March 21, 2008 1:57:46 PM

Underclock said:
i would use the search, but anything i try, i get

"Your search must be three characters long at least "

Yeah, I hate the search engine here sometimes
March 21, 2008 3:56:59 PM

Thanks everyone!

According to what you guys say and to those links, it seems i dont actually "need" to match FSB with mem, giving a memory divider of 6:5 can be used for DDR2-800 (FSB 333), for instance, or doing a minor overclock so i get a base value of 400 for the FSB (over 333) and still keep the 1:1. i could even gor for DDR2-1033 using a 8:5 divider.
right?

i'm thinking of an E8400 processor for, which would need DDR2-667, but now i guess i can go for 800 without problems. i've seen many people say this cpu can safely be overclocked to 4GHz...

i dont know the multipliers, but i'm guessing 8400's 3Ghz works by doing 9*333? so i could overclock by doing 9 or 10*400? how would the memory fit then? the DDR2-800 would adjust better then, right? and then maybe i could still have some benefit by using DDR2-1006?

it's so confusing :( 

i'll be using it for gaming, but i'm not an over-the-top gamer, so i dont need super performance, but i want to know what configs i can use in the long run without having to rebuy equipment (i upgrade my pc every 3 years or so, so i might be doing some OC in like 2 years if i must).

Tks!
March 22, 2008 4:42:32 PM

so... am i right in my thoughts?
i really need to know this :( 
March 22, 2008 5:05:51 PM

Underclock said:
so... am i right in my thoughts?
i really need to know this :( 

well, there's no point in going out of sync (keep the 1:1 ratio if you can)

you have the right idea when it comes to the multipliers, but i think that the E8400 only has a 9x multi MAX. that means you need to push the fsb farther to reach 4.0ghz. It would need to be 9x444, which is much more stressful. You can get the higher rated ram if you like, and tighten up the timings if your not going up to a 500fsb! (which you won't)
March 22, 2008 7:24:13 PM

oh, cool :) 
cause i've seen people say they buy 800 ram and that the system would "downrate" them to 667 so they'd keep the 1:1. and since they're native 800, it'd allow future OC to the FSB and still allow 1:1 synch.

how much of this is true?
a b V Motherboard
March 22, 2008 7:48:11 PM

Go with Bus speed of 400. With E8400 using 9X this will give 3.6 GHz. Then using DDR2 800 CL 4 you will have your 1::1.

I'm currently using E6400, Bus of 400 for 3.2 GHZ. Am using DDR2 800 CL4 with a 1::1 ratio (FSB = 1600)

Note 4 Ghz is only 11% gain over 3.6 GHz
March 22, 2008 9:57:24 PM

but can I "downgrade" DDR2-800 memory to make it work like 667 and keep the 1:1 synch so that when i want to OC in the future, i can readjust the FSB and mem back to previous values?
tks.
March 22, 2008 10:12:12 PM

Underclock said:
Thanks everyone!

According to what you guys say and to those links, it seems i dont actually "need" to match FSB with mem, giving a memory divider of 6:5 can be used for DDR2-800 (FSB 333), for instance, or doing a minor overclock so i get a base value of 400 for the FSB (over 333) and still keep the 1:1. i could even gor for DDR2-1033 using a 8:5 divider.
right?



How is that will benefit a cpu or the whole system (performance wise) itself for DDR2-1033 using a 8:5 divider? its a wasted bandwidth and a loose timings... Is it not better to have a 1:1 ratio with a tight timings?
March 22, 2008 10:29:39 PM

that's percisely my doubt :) 
!