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1:1 Memory Ratio

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December 30, 2006 9:53:15 PM

I just bought a new pc and i am trying to figure out what OC i should do to utilize my components capabilities.

What i havent been able to figure out (after alot of reading :(  ) is i bet very basic: everywhere i read its best to keep the Memory Ratio to 1:1.

What gets me confused is that some say C2D 6600 CPU clock at 266 x 2 = 533MHz DDR2 RAM for 1:1, others say CPU 266 x 4 = 1066MHz DDR2 RAM for 1:1. Obviously i misunderstood something there, i have no experience at all in this, and this propably is something that everyone knows the answer to except me :?

The components i have are:

M/B: ASUS P5W DH Deluxe
RAM: 2x1Gb Cellshock DDR2 800 4-4-4-12
CPU: C2D 6600
HD: WD 150Gb 10000Rpm
GPU: XFX 8800 GTX
PSU: Zalman 600W
CPU fan: Stock
Case: Antec 900, 2 front 120mm, 1 rear 120m, 1 top 200mm fan

My aim is to OC as much as needed to achieve 1:1 without buying extra cooling if thats possible.

So the queston is, do i have to get CPU clock from 266 to 400MHz in order to have 1:1 for the DDR2 800? I guess/hop not, but cant really clarify this myself so any advice will be very helpfull.

More about : memory ratio

December 31, 2006 8:40:33 AM

Read Wusy's overclocking guide in the OC/CPU section :) 

Its not always possible to reach 400fsb but you can run your ram slower to utilise the 1:1 harmony.
December 31, 2006 8:48:25 AM

Well after some more reading i draw the conclusion that to use DDR2 800 at 1:1 i do have to go from 266MHz to 400MHz, which means 3.6GHz CPU speed for C2D 6600.

What got me confused was a post stating that with 293MHzx4=1172MHz FSB 1:1 was achieved with a DDR2 1000 OCed to 1172.

From what i read, its not possible to reach 400MHz without extra cooling and alot of effort. So if i go for example 333MHz, should i set DDR2 to 667 or keep at 800 and not have 1:1? What will perform best?
Is it better to drop the CPU multiplier from 9 to say 8 and go to 400MHz in order to achieve 1:1 and to 3.2GHz instead of 3.6GHz and will that OC be stable with my current config?

And if this is the case, whats the use of DDR2 1150MHz? Is it even possible to get 1:1 so high even with the best cooling? And if 1:1 is not achieved, is the extra RAM speed just a waste of money since the FSB will bottleneck the RAM?
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December 31, 2006 8:51:23 AM

Quote:
Read Wusy's overclocking guide in the OC/CPU section :) 

Its not always possible to reach 400fsb but you can run your ram slower to utilise the 1:1 harmony.


Thanks for the reply.

Is it easier to reach 400MHz if i drop the multi from 9 to 8?
December 31, 2006 8:58:03 AM

Im no expert (overclocked my first rig this month ^^) but im confident in saying that dropping the multiplier does not make it easier to reach a higher fsb.

Again, no expert but one use for > 800MHz modules is that you can drop their speed and maintain much tighter timings. Im not sure if this is the case for all ram but my 800MHz c4 ram, according to cpu-z is rated at 4-4-4-12 @ 266Mhz and only 5-5-5-18 @ 400MHz so since ive hit my wall (personal choice) at 340fsb im running the ram at 680MHz but with 4-4-4-12 timings. Dont ask me how much difference there is between 4 and 5 :p 
December 31, 2006 9:43:27 AM

So is anything above DDR2 667MHz a waste for a noob with no desire to push to the limit like me? :o 

The majority of buyers will never OC, yet i'm under the impression that DDR2 800MHz is the best seller.

Since my Cellshock stock timings are 4-4-4-12 at 800MHz, is there any link to check out what timings i should use for say 667MHz and will there be any real improvement?
December 31, 2006 9:53:45 AM

800MHz is popular here because most will overclock to a degree however i would highly doubt 800MHz is common amongst Dell and the like :( 

I would recommend to anyone with a C2D and good 667/800 ram to overclock the cpu to 333fsb because its extremely simple and can be done in a single jump. It may not be so for everyone but I did it with no adjustment to any voltages etc. Simple. Shaved 4 secs off my SuperPI time (im not one for "wow a whole 4 secs in a benchmark" but its a good indication of the percentage gain).

Could anyone else answer this :
Since my Geil 2gb pc6400 c4 ram is rated so @ 266 and c5 @ 400 would this also be the case that 667MHz c4 modules would be rated c4 @ 266 and c5 @ 333?

For the price i got my 800MHz c4 ram I cant complain but perhaps it would normally be wiser to buy 667 c4 if you only plan to overclock to 333fsb.
December 31, 2006 11:34:43 AM

From what I understand, if you run your FSB up to 333 and you have 800 RAM you will need to UNDERCLOCK your RAM down to 667 to run 1:1. Uou should be able to keep the 4-4-4-12 timings.
December 31, 2006 11:35:21 AM

Don't worry much about that 1:1 ratio. Don't affect the computer's performance. I know I have tried it myself, and I'm better of with lower memory and higher cpu frequency. If you're overclocking find the best stable settings and stick with it. As for mine I got 4Ghz of my 3.2Ghz 800fsb cpu with DDR2 533 on 200. A lot faster then my 1:1 setting of 450.
December 31, 2006 12:29:25 PM

Hope this will help...

The CPU runs at - the FSB times the multiplier (stock E6600 is 266 x 9)
The EFFECTIVE front side bus is "quad-pumpled" so FSB x 4 = 1066 (this is why core 2 duo say FSB = 1066)
Ram is runs at the actual FSB (not quad-pumped so 266) X 2 because it's DOUBLE DATA RATE time the ratio.

In a stock set-up of an E6600 you have...
CPU = 266 X 9 = 2400
FSB = 266 X 4 = 1066
RAM = if it's 533 = 266 x 2 in a 1:1, if it's 667 = 266 X 2 x ratio, if it's 800 = 266 x 2 x a higher ratio....

When you OC you change the default FSB from 266 to something higher which effects all these components. If you don't manually set the ratio to 1:1, you will be overclocking the RAM regardless of the what number you set the FSB to. BUT... if you manually set it to 1:1 and your running RAM that's faster than 533 you'll be uncderclocking it until you reach a FSB that is half of the RAMs designated speed.

FSB = 333
Memory Ratio = 1:1
RAM = 666

If you don't set the ratio to 1:1 then you will most likely run out of headroom on the RAM before you reach the maximum overclock of the CPU and chipset.

If you don't want to run the FSB much higher than 333 than 667 RAM is good enough, if you go much higher you'll need 800, although most RAM will overclock some so you could probably get 350 FSB or so from 667.
January 1, 2007 6:17:45 PM

Good explantaion, MAK-Daddy.

I see no reason why the OP shouldn't be able to hit a 400FSB with his set up. With the memory set to run 1:1, he's golden. True, not all CPUs will OC the same, but 400 should be obtainable.

Many don't recommend jumping in head 1st. In other words, do your OCing in small steps. Personally, I jumped straight to a 400FSB. It worked for me, and others too from posts I've read. Not sure I'd advise it to others. Maybe I just got lucky. :)  I did have to bump the voltage on the memory from 1.8 to 2.0, but currently running under the default vcore.
Anonymous
a b à CPUs
a b K Overclocking
January 3, 2007 2:37:52 AM

Since he has a E6600 he will need a much better CPU cooler.

Nobody talked about lowering the multiplier, 7X400@2.8ghz would still be an overclock =).
Edit:o ops can the P5WDh do it?

Anyway, I say 3ghz 333FSB memory at 667Cl4 should be pretty good. Don't know if the stock cooler can do it.
Artic Freezer Pro 7 is not that expensive....
January 3, 2007 4:28:17 PM

Thanks for the replies.

The multiplier can be set from 6 upto 9 on the p5w dh with the latest bios version 1707.

I definetely need better cooling before i even attempt the slightest OCing :cry: 
Atm core temps rise upto 60C peaking shortly at 62C (coretemp) while running orthos. Thats on default 266MHz.

The box got a bit congested after i added 2 old hard disks, blocking the airflow from the 2nd front case fan which is sending the air on the cpu and adding 2 to 4 degrees more (used to reach 58C before).

I will add a 5th 120mm fan on the side of the case, blowing air on the GPU and CPU and change the stock CPU cooler with an Artic Freezer Pro 7 a friend has but cannot use due to space problems :wink:

I hope this will drop the temps atleast 10C.

Sidenote: Setting case fans to high (3step antec fans) drops the temps by about 4C but the noise is like a vacum cleaner :cry: .
I OCed at 333MHz without the 2 extra HDs and with case fans at high and got core temps of 64C so not much OC room with stock cpu cooler.

Until i get better cooling, is it better to set the ram at 800MHz and not have 1:1?
January 3, 2007 4:37:33 PM

Yes, the gains from 800Mhz RAM at stock FSB speeds are minimal, but they are there. Definately better than underclocking the RAM just for the sake of a 1:1 ratio.
January 5, 2007 6:05:32 PM

Ok I'm starting to get this 1:1 ratio thing. But I'm planning only OC'ing my e6400 to 333 fsb for now. And would'nt that mean that my Corsair XMS2 ddr2 800 would be running at a slower 667 speed. Would it be beneficially to set at a 4:5 so my ram is clocked higher? or would it be beter to just set the ram at stock 800 and the cpu at 333fsb?
January 5, 2007 6:20:01 PM

If you set the RAM at 800 and then overclock the FSB to 333 your RAM will be running much higher than 800. Memory Speed = FSB x Ratio X 2.

Some BIOS lists the actual ratios for RAM speed, my DS3 for instance has a choice of AUTO, 2 (which is really the 1:1, because after the x2 for double data rate the ration becomes 2:1), some mother motherboards list memory speed instead of a ratio but it's really a ratio... confusing? absolutely. If you set the memory to 800, its only really at 800 at the stock FSB settings.

That said, you can try running the FSB at 333 and the leaving the ratio at something higher than 1:1 (or 533) and see if it's stable. If it is, it's not going to hurt anything. But, you'd probably see better performance at the same processor speeds by going 400 on the FSB and lowering the multiplier to 7 or 8.
January 5, 2007 6:41:11 PM

Quote:
But, you'd probably see better performance at the same processor speeds by going 400 on the FSB and lowering the multiplier to 7 or 8.


This is something i was thinking of trying when i upgrade my cooling.
Will the lower cpu clock result in lower cpu temps?
Is a c2d 6600 runing at 8x400=3.2GHz the same as 9x355.55=3.2GHz in terms of cpu temps, performance, cpu voltage etc?
I guess the 8x400 will result in better ram performance as MAK-Daddy32 says, but will the lower multi also make the FSB OC easier?
I'm guessing this could be one of those "it depends on your cpu/system etc" kind of questions, has any1 tried a comparison on this?
January 5, 2007 8:24:13 PM

Quote:
If you set the RAM at 800 and then overclock the FSB to 333 your RAM will be running much higher than 800. Memory Speed = FSB x Ratio X 2.

Some BIOS lists the actual ratios for RAM speed, my DS3 for instance has a choice of AUTO, 2 (which is really the 1:1, because after the x2 for double data rate the ration becomes 2:1), some mother motherboards list memory speed instead of a ratio but it's really a ratio... confusing? absolutely. If you set the memory to 800, its only really at 800 at the stock FSB settings.

That said, you can try running the FSB at 333 and the leaving the ratio at something higher than 1:1 (or 533) and see if it's stable. If it is, it's not going to hurt anything. But, you'd probably see better performance at the same processor speeds by going 400 on the FSB and lowering the multiplier to 7 or 8.


If my math is correct, if you were planning to run a 333 FSB, you could set your memory as 667 in BIOS, and that would give you 832 MHz on your memory, which would be only about a 4% overclock of the memory. I would think you could run the advertised timings at that speed.
Anonymous
a b à CPUs
a b K Overclocking
January 5, 2007 9:25:19 PM

The CPU temps are closely related to the VCore(voltage of the CPU). I found that different OC with the same VCore result in pretty close temperature.

So lowering the clock speed allow for lower voltage thus reducing temperature.

The different memory speed should not be that much of an impact on the cpu temps but more on the NorthBridge and ram temperature.

If you are using a P5B you might be better off with a 355FSB stability wise. The P5B is at the edge of the northbridge stability at 400MHz(has to do with the 1066 Strap being pushed to the max, fall back to 1333 Strap).
So if the systems seams unstable and you try to pump more juice it might raise the temps.

Hope this answer you question!

To the OP: The Core 2 Duo really doesn't starve on bandwith, I wouldn't worry that much. You could always set it to 6 X 400 resulting in 1:1 and 2.4 which shouldn't add any heat.

When you get a better cooler you could look at setting such as 8 X 366, you could then tighten the timing and get a good OC!
a b à CPUs
a b K Overclocking
January 5, 2007 9:53:02 PM

Check out the following THG article:

http://www.tomshardware.com/2006/03/31/tight_timings_vs...

Here is a 3.2Ghz setting for 367Mhz FSB at a 4:5 ratio for DDR2 918Mhz. DDR2 800 - C4 memory changes from 2.0v to 2.15v and from 4-4-4-12 to 5-5-5-15. This is a snappy configuration for OC quality DDR2 800 C4 memory, because the increase in ratio from 1:1 to 4:5, and the resulting increase in frequency from 733Mhz to 918Mhz, slightly outweighs the increase in latencies from 4 to 5. :D 
January 5, 2007 11:11:14 PM

Thanks to all, i got all my questions answered, atleast until i get the better cooling and actually start testing :) 
January 5, 2007 11:14:39 PM

Ok so what I get from this is that the most beneficial setup, in my case with a e6400 and xms2 ddr2800 would be to lower the memory clock to 667mhz creating a 4:5 ratio. Then raising my CPU fsb to 333mhz. This would slightly overcock my ram instead of running at a slower 1:1 ratio speed and ,if stable, bring the best performance?
a b à CPUs
a b K Overclocking
January 5, 2007 11:58:19 PM

Quote:
Ok so what I get from this ... is to lower the memory clock to 667mhz creating a 4:5 ratio. Then raising my CPU fsb to 333mhz. This would slightly overcock my ram instead of running at a slower 1:1 ratio speed and ,if stable, bring the best performance?


I think you have the right idea, but if expressed as:

E6400 @ 2.67Ghz = 8 x 333 FSB @ 1:1 ratio = DDR2 667Mhz @ C3.
E6400 @ 2.67Ghz = 8 x 333 FSB @ 4:5 ratio = DDR2 833Mhz @ C4.
or...
E6400 @ 2.93Ghz = 8 x 367 FSB @ 4:5 ratio = DDR2 918Mhz @ C5.
or a real memory stretch...
E6400 @ 3.0 Ghz = 8 x 375 FSB @ 4:5 ratio = DDR2 938Mhz @ C5.

This what you had in mind. 8)
January 6, 2007 5:04:17 AM

Quote:
Ok so what I get from this ... is to lower the memory clock to 667mhz creating a 4:5 ratio. Then raising my CPU fsb to 333mhz. This would slightly overcock my ram instead of running at a slower 1:1 ratio speed and ,if stable, bring the best performance?


I think you have the right idea, but if expressed as:

E6400 @ 2.67Ghz = 8 x 333 FSB @ 1:1 ratio = DDR2 667Mhz @ C3.
E6400 @ 2.67Ghz = 8 x 333 FSB @ 4:5 ratio = DDR2 833Mhz @ C4.
or...
E6400 @ 2.93Ghz = 8 x 367 FSB @ 4:5 ratio = DDR2 918Mhz @ C5.
or a real memory stretch...
E6400 @ 3.0 Ghz = 8 x 375 FSB @ 4:5 ratio = DDR2 938Mhz @ C5.

This what you had in mind. 8)

Yep that is what I was thinking. I have default cl4 ram so I shall try and see how I fair on monday when the rest of my computer parts arrive.

Thanks for help
January 8, 2007 7:36:08 PM

Hello,

My P5B dlx uses DDR2 at 800 Mhz, 1:1 ratio (DDR2-533 Mhz). My E6400 multipl. is lowered to x6 instead of x8, thanks to the bios, and with FSB = 400 Mhz (perfectly stable). Hence, cpu works at 2.40 Ghz, so this is a very limited core overclocking. Which allows me to set VCore at only 1.2 V with very few heat and noise and always perfectly stable.

Since those modifications, I have noticed gains in performance in some memory hungry games like Oblivion, F.E.A.R. of 25 % !

Changing DDR2 timings from 5.5.5.15 to 4.4.4.12 for example bring little improvement, 2 ou 3 % IMO...

Just one big thing : watch the northbridge's temperature !!
January 12, 2007 4:00:17 PM

hey so i'm new to overclocking: :wink:

default settings are
c2d e6700 @ 266mhz x10 = 2.66ghz
evga 680i
266 * 4 =1066 mhz FSB
memory at 1:1 default? = 266 x 2 = DDR2 533

i have 2gb of DDR2 800 RAM, so at default its actually at 533?

so.... i've reached 3.7 ghz oc (370 x 10) @ 1.55Volt vcore
370 x 4 = 1480 FSB @ 1.4Volt
stable under p95 for ~20 min. til i stop it.
the ram at a 4:5 ratio is at 925 mhz @ 2.0Volt (doable for my corsaire twin2x2048 with the LED lights i think)
(370 * 1.25 * 2 = 925 mhz)

Question:
would i get better TOTAL GAMING performance if i
raise FSB to 400 and lower multiplier to 9x for a 3.6 ghz clock and have a 1:1 800mhz ram? with obviously lover vcore volts?

is my vcore too high? its with in recommended tollerances i think, i get 42° idle 55° load.
January 14, 2007 1:46:01 PM

That's correct for 533 Mhz

3.6 Ghz with low vcore, seems difficult to reach those heights. Depends also of your cpu... Every cpu has different overclocking potentials. With my E6400, I can reach 3 Ghz with 1.25 V, but 3.4 Ghz or more need 1.4 V.

1:1 will give you the best bandwidth (533 Mhz) but will give a lot of stress on the northbridge with very high FSB. I had to make a choice : put a hudge fan straight on the northbridge or lower the FSB... Guess what's my choice...

4:5 is a good compromise (means DDR @ 667).

42° C idle is fuction of your room temp. If you get 42° at 25 ° ambient, that's correct. If ambient is actually 19 °, I can't imagine what will happen at 30 ° ! ;)  55 ° C at load is acceptable (given max temp of 61 - 65°)

By curiosity, are you using stock intel cooler ?
January 14, 2007 3:36:53 PM

What nobody seems to have mentioned is DUAL CHANNEL.

I'm assuming that you have 2 stick of 1 gig, because 2 gig is rare.

Thus you probably have your RAM in dual channel configuration (if not you are a n00b).

This means that DDR2 533, DOES, in fact, run at 1066mhz!

266*2*2=266*4=1066mhz.

Or have I somehow got this wrong?

It would be quite frustrating that none of you knew this if I am right.
Anonymous
a b à CPUs
a b K Overclocking
January 15, 2007 2:18:03 PM

You are right but the point is that the ram does run at 533 matching the CPU bandwith in dual channel.

It does not run at this speed though, it run at a actual 266 like in your formula
June 11, 2009 4:44:10 AM

MAK-Daddy32 said:
If you set the RAM at 800 and then overclock the FSB to 333 your RAM will be running much higher than 800. Memory Speed = FSB x Ratio X 2.

Some BIOS lists the actual ratios for RAM speed, my DS3 for instance has a choice of AUTO, 2 (which is really the 1:1, because after the x2 for double data rate the ration becomes 2:1), some mother motherboards list memory speed instead of a ratio but it's really a ratio... confusing? absolutely. If you set the memory to 800, its only really at 800 at the stock FSB settings.

That said, you can try running the FSB at 333 and the leaving the ratio at something higher than 1:1 (or 533) and see if it's stable. If it is, it's not going to hurt anything. But, you'd probably see better performance at the same processor speeds by going 400 on the FSB and lowering the multiplier to 7 or 8.


sir i cant understand this,

what do you mean that the memory= fsb x ratio x 2?

flyinformula said that he will try to set his fsb to 800 and his ram frequency at 800 right?

you said that the memory will run higher than 800,

i cant understand how the 800 will go much higher than 800 sir,..

can you please help me about these
T_T,...

thx..
June 11, 2009 8:37:12 PM

dude look at the dates.


This sure is happening a lot lately.
June 15, 2009 2:41:18 PM

im fine man^_^

i totally understand memory ratio ^_^ tnx..
!