# Overclock CPU then Underclock Memory?



## ALP1987 (Feb 14, 2010)

Alright i overclocked my Quad Q6600 from 2.4ghz to 3.0ghz (G31T-M wouldn't allow any further) the other day (thanks to those that helped here). I was reading a few other forums and someone was saying that with a FSB of 1333 a person should Under/Downclock their 800Mhz memory to 667mhz and lower the CAS Letency. Is this true? What would be the benefits?

If so my memory is OCZ 800mhz rated at 4-4-4-15. If i were to lower it to 667mhz should i lower my CAS and if anyone has done so what should be the times?

Also for some reason after i OC'ed my Q6600 my memory times changed to 5-6-6-15. Why would it do that?


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## Black Panther (Feb 14, 2010)

When you overclock the FSB automatically your memory would go up from 800Mhz to more. You can check out at what Mhz your memory is currently running if you run cpu-z.

Now that can limit your overclock, because let's say that hypothetically your memory can't go higher than 850Mhz then you'd be stuck.
Now if you put the RAM speed at 667, you might be able to overclock more (mobo and cpu permitting) since you'd be 'starting' at 667 and going up to 850, not starting at 800.

As an example, I got my memory also 800Mhz. To oc my E8400 from 3Ghz to 4Ghz I downclock my ram to 667, and when I have my processor at 4Ghz the ram would be running at 890Mhz! It would have been never possible for me to achieve the 4Ghz cpu clock had I not downclocked the RAM because I doubt my ram would be able to go over 1066Mhz.


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## Bo$$ (Feb 14, 2010)

ALP1987 said:


> Alright i overclocked my Quad Q6600 from 2.4ghz to 3.0ghz (G31T-M wouldn't allow any further) the other day (thanks to those that helped here). I was reading a few other forums and someone was saying that with a FSB of 1333 a person should Under/Downclock their 800Mhz memory to 667mhz and lower the CAS Letency. Is this true? What would be the benefits?
> 
> If so my memory is OCZ 800mhz rated at 4-4-4-15. If i were to lower it to 667mhz should i lower my CAS and if anyone has done so what should be the times?
> 
> Also for some reason after i OC'ed my Q6600 my memory times changed to 5-6-6-15. Why would it do that?



i have the same issue except i want to overclock my memory to 800MHZ and push CPU to 3.6 GHZ

doesn't running it at 667 not allow you to OC further due to linked FSB ?


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## digibucc (Feb 14, 2010)

Bo$$ said:


> i have the same issue except i want to overclock my memory to 800MHZ and push CPU to 3.6 GHZ
> 
> doesn't running it at 667 not allow you to OC further due to linked FSB ?



well it's linked, but not entirely.  both the cpu and the and the memory can be affected by the core clock, and their multipliers.  the core clock is determined by the FSB - but you should still be able to change the memory multiplier to make it run lower, ie at around 800 as it's supposed to (not exactly)

my CPU is rated at 2.67GHz, my ram at 1600MHz - when I overclocked my cpu by using the FSB clock, to 4GHz - it also changed my RAM to over 2000MHz - I changed the ram multiplier and now it runs at 1603MHz stable.

it may not say multiplier in the bios, but that is what the option changes.  I am not sure exactly what it will say in your bios, sorry.


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## ALP1987 (Feb 14, 2010)

My board has a max FSB of 1333 so that's why i say im stuck at 3.0ghz. My memory tho is the OCZ DDR2 800mhz but like i said i've read that if i lower the memory to 667mhz it will better utilize the 1333FSB and i could also lower the Cas Letency which would make things faster. My Bios reads like this for the memory.

DRAM Frequency: 800mhz (want to change to 667mhz)
Configure DRam Timing By SPD: Enabled (Disable if i want to choose the CAS) 
DRAM CAS# Letency: 5
RAS To CAS Delay: 6
RAS Precharge: 6
RAS Active To Prec: 15

Again the rated times were 4-4-4-15 so if i lower it to 667mhz could i presumably go with 3-3-3-14(or lower)?


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## ALP1987 (Feb 14, 2010)

Heres what CPU-Z says


DRAM Frequency: 414mhz
FSB;DRAM: 4.5
CL: 5
tRCD: 5
tRP: 5
tRAS: 13
tRFC: 36
Command Rate: 2T


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## Black Panther (Feb 14, 2010)

ALP1987 said:


> My board has a max FSB of 1333 so that's why i say im stuck at 3.0ghz. My memory tho is the OCZ DDR2 800mhz but like i said i've read that if i lower the memory to 667mhz it will better utilize the 1333FSB and i could also lower the Cas Letency which would make things faster. My Bios reads like this for the memory.
> 
> DRAM Frequency: 800mhz (want to change to 667mhz)
> Configure DRam Timing By SPD: Enabled (Disable if i want to choose the CAS)
> ...



Keep it at 5-6-6-15 for now and at 667.
Overclock.
When you reach the max, try lowering the timings.


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## sneekypeet (Feb 14, 2010)

I think he means he can only set the boot strap to 1333 with no actual FSB control after it.

What I believe he is asking is....is it better to run his ram at 800mhz or 667mhz with no option to go further after changing the divider.

IMHO unless your board has the ability to run 667Mhz at CAS3, I would leave the ram at 800mhz.

After looking a w1zzards review http://www.techpowerup.com/reviews/ECS/G31T-M/6.html I saw that his ECS does have FSB control, but no CPU voltage, so that is what is his limiting factor.


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## ALP1987 (Feb 14, 2010)

sneekypeet said:


> I think he means he can only set the boot strap to 1333 with no actual FSB control after it.
> 
> *What I believe he is asking is....is it better to run his ram at 800mhz or 667mhz with no option to go further after changing the divider.
> *
> ...



Correct. I'm limited to my maximum FSB being 1333 so just wanted to know if its better to run the memory at 667mhz with a potential lower CAS rather than at 800mhz with a 5 CAS.


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## sneekypeet (Feb 14, 2010)

667 with CAS4 will be about the same as 800 CAS5 in my opinion. Best thing to do is try to set the lowered timings and see if the system is stable.  

I suggest going and burning an ISO of memtest86+ version 4.0 (google it) and running to see if its stable before exposing the HDD to unstable ram. In the long run unstable ram can corrupt a HDD and make way more work for you later.

IF in fact everything is good at this point, use memory benches like SuperPi Mod1.5, Wprime, or the Everest memory and cache bench both now and after so you have some comparative results. If the times drop in SuperPi or Wprime, you are making headway (getting faster ram speed) in the everst bench you want higher numbers, they signify better performance. Hope this helps.


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## ALP1987 (Feb 15, 2010)

Alright i went from 333 to 340 which now is a 3.05ghz CPU OC and the memory is set at 667MHZ with 4-4-4-15 settings but CPU-Z has it registering as 424MHZ (828mhz) with 4-4-4-15 settings and a 2T command rate.

I used memtest86 4.0 and let it do a single pass and it found 0 errors. I've never used MemTest before so should i let it do more than 1 pass?

Also since i set the settings at 667Mhz and OCed my CPU to 3.05ghz the memory is now running just 28mhz above the standard MHZ so this shouldn't create any more wear and tear/heat issues with the memory?


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## sneekypeet (Feb 15, 2010)

One pass is a quick go, but most suggest running it overnight

CPU-z is most likely reading it correctly.

Any overclocking will create more wear and tear, but 28mhz and a timing drop wont make it catch fire or anything


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## ALP1987 (Feb 15, 2010)

sneekypeet said:


> One pass is a quick go, but most suggest running it overnight
> 
> CPU-z is most likely reading it correctly.
> 
> Any overclocking will create more wear and tear, but 28mhz and a timing drop wont make it catch fire or anything




Really overnight? 28mhz was a typo. It should have been 48mhz. I could just take the CPU down until i hit 400mhz on my memory so that its not OCed. Even tho it will be running 800mhz from the 667mhz slot it would still be the stock 800mhz speed so it shouldn't create any issues right? I shouldn't lose much speed and it would still be an improvement over the stock 2.4ghz for the CPU. Its probably the best and safest way to go.


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## Bo$$ (Feb 15, 2010)

digibucc said:


> well it's linked, but not entirely.  both the cpu and the and the memory can be affected by the core clock, and their multipliers.  the core clock is determined by the FSB - but you should still be able to change the memory multiplier to make it run lower, ie at around 800 as it's supposed to (not exactly)
> 
> my CPU is rated at 2.67GHz, my ram at 1600MHz - when I overclocked my cpu by using the FSB clock, to 4GHz - it also changed my RAM to over 2000MHz - I changed the ram multiplier and now it runs at 1603MHz stable.
> 
> it may not say multiplier in the bios, but that is what the option changes.  I am not sure exactly what it will say in your bios, sorry.



but the minimum is 1:1 ratio? i run CPU at 333MHZ and RAM 333MHZ is it possible to overclock the CPU more with out changing the memory? every time i try and push it further it wont boot,

and ALP: overnight is the best option to maximise the stability


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## hat (Feb 15, 2010)

It's simple really. In order to overclock the CPU, you have to raise the FSB. If you raise the FSB, your memory frequency increaces along with it. Generally speaking, when you're overclocking your processor, you want to make sure the processor is the only thing being pushed, so you drop the memory speed to keep it at or below stock. That way, the stability of the memory remains intact, and when you're testing for stability and it fails, you can be fairly certian the processor needs more juice, or you've pushed the FSB too far and your board can't handle it.

Once you've made sure the processor is stable where you want it, you can start playing around with the memory frequency if you want... that way, if the test fails, you'll know it's the memory since you've already validated the processor's stability.


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