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Should I run DDR2 800 RAM at 533Mhz?

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March 12, 2007 1:25:37 AM

I am upgrading the major components of my computer(processor, video card, ram, hard drive) and I purchased Corsair XMS 6400 C4D DDR2 800 ram to run with my E6600. I plan to overclock the processor, but not to its max, just a bit maybe to 2.6Ghz or so.

I have been reading about the whole 1066 front side bus issue and that 533 ram x2 meets this perfectly, my question is this: What are the benefits or downfalls of underclocking my DDR2 800 to 533Mhz and is it necessary to do this to overclock the cpu or is it for stability?

Thanks ahead of time for the help.
-Rigya
March 12, 2007 1:47:42 AM

The downfall is that you have slower RAM. There will be no stability issues if you overclock you CPU correctly. Leave the RAM alone and OC the CPU first. Once you have achieved a stable OC move on to the RAM. That way you can simplify troubleshooting if you need to.
March 12, 2007 1:52:43 AM

Is it possible to overclock the cpu to say 2.7Ghz and manually set the ram to back to 800 or would it automatically overclock the ram again?
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March 12, 2007 2:01:01 AM

I don't follow... Overclock the CPU without messing with the RAM. Once you have attained a stable 24 Hour Prime95 test, then you can begin to overclock the RAM if you so desire. Since you will be OCing the CPU I would OC the RAM as well. The one thing you must do is buy an aftermarket HSF (Heat -synk & fan). Was that what you were asking?
March 12, 2007 2:13:07 AM

Quote:
I have been reading about the whole 1066 front side bus issue and that 533 ram x2 meets this perfectly, my question is this: What are the benefits or downfalls of underclocking my DDR2 800 to 533Mhz and is it necessary to do this to overclock the cpu or is it for stability?

Is it possible to overclock the cpu to say 2.7Ghz and manually set the ram to back to 800 or would it automatically overclock the ram again?



Yes you will see an increase in write bandwidth by running the ram 1:1, but read bandwidth wont get any better (at least thats what i remember from reading up)

most motherboards will allow you to set a certain ratio to set the ram close to the original speed, eg if you were running your fsb at 1066 and your ratio was 4:5 then the ram would run at 850, or @ 2:3 it would run the ram at 710 mhz



i hope this helps
March 12, 2007 2:17:20 AM

The RAM will synchronize with the FSB. It's better to start low say a 1:2 or a 1:1 FSB:RAM. If you set it at 800MHZ before overclock with a FSB of 1066 (266 quad pump) it'll be 2:3 FSB:RAM. So if you start overclocking at that FSB:RAM ratio, you'll immediately hit RAM speed over the its specs which is not safe.

You'd start by setting your RAM speed to 533 or 667 MHz for 1:1 or 1:2 and be safe with your RAM.

And Rigya why do you want to just OC to just 2.6GHz? You can easily achieve 3.0 GHz with stock voltage.

If you don't want to synchronous your FSB:RAM, you should consider the RD600 chipset which feature asynchronous RAM so you can OC and not worry about it automatically setting your RAM speed (DFI Lanparty ICX3200)

Or you could OC to 400Mhz bus speed (1600MHz FSB Quad pumped) and dail down the CPU multiplier to 7x for 2.8GHz CPU speed and 800Mhz RAM speed, 1:1)
March 12, 2007 2:20:25 AM

Sorry I didn't give as good of advice as Nossy but I am tired.
March 12, 2007 2:22:52 AM

oops, got the ratio the wrong way around
sorry bout that
March 12, 2007 2:23:56 AM

I was wondering about that... :D 
March 12, 2007 2:27:16 AM

Thank you all for your help this is exactly the stuff I need to know. I was only aiming to OC to 2.6 or so because I am worried about the stress on my hardware. I have an aftermarket cpu cooler and I use a 3 slot 5.25in fan in the front with a 120mm fan which pushes air right over the ram and cpu.

I am glad to hear about being able to down the multiplier to x7 at 400Mhz and have a 1:1 with my ram. Will this setup be effective or would it be recommended to do it another way?

Thanks again.
March 12, 2007 2:28:58 AM

Another satisfied customer! :D 
March 12, 2007 3:11:45 AM

Quote:


I am glad to hear about being able to down the multiplier to x7 at 400Mhz and have a 1:1 with my ram. Will this setup be effective or would it be recommended to do it another way?

Thanks again.


yeh no doubt that would be a good setup, in fact i would set it up that way. syncro all the way! Very effective
March 12, 2007 3:28:38 AM

One final question: Would this all be possible with stock voltages or should I up the voltage on something and what?
March 12, 2007 5:20:56 AM

Quote:
One final question: Would this all be possible with stock voltages or should I up the voltage on something and what?


well, the memory will be running at its normal speed, so dont worry bout that. cpu wont need v if youre only going to 2.6. Just go for it. :) 
March 12, 2007 6:52:16 AM

Or you could OC to 400Mhz bus speed (1600MHz FSB Quad pumped) and dail down the CPU multiplier to 7x for 2.8GHz CPU speed and 800Mhz RAM speed, 1:1)

Should that be: 800Mhz RAM speed, 1:2) ?

Since 1:1 would be 400Mhz and therefore 400Mhz Ram speed.

I am new to overclocking so I am not sure if I am not understanding this right, or if it is incorrect.
March 12, 2007 11:35:42 AM

Quote:
Or you could OC to 400Mhz bus speed (1600MHz FSB Quad pumped) and dail down the CPU multiplier to 7x for 2.8GHz CPU speed and 800Mhz RAM speed, 1:1)

Should that be: 800Mhz RAM speed, 1:2) ?

Since 1:1 would be 400Mhz and therefore 400Mhz Ram speed.

I am new to overclocking so I am not sure if I am not understanding this right, or if it is incorrect.


Ah yeh, close.
Youve forgotten that ddr2 is double pumped, so ddr2 800 is actually clocked at 400mhz
March 12, 2007 1:00:06 PM

Either way, if you overclock, you'll put stress on any of your hardware. If you overclock by pumping up the bus speed to 400MHz (1600MHz FSB), and turning down the multiplier, you'll be putting stress on your motherboard because the northbridge will run hot and may need an increase in voltage to run stable (and sometime requiring active cooling over the northbridge). Overclocking this way you'll just put less stress on your CPU and more stress on your northbridge.

You can play around with the CPU multiplier/FSB/RAM combination and find one that will achieve what you want. But remember that not all motherboards will allow you to change the multiplier, and only the Extreme Edition processors such as QX6700 and X6800 will allow you to increase the multiplier.

But one recommendation I'd give you is to sync your Bus speed to RAM at 1:1 before you overclock to give you best result. It won't hurt to run your RAM below its rated clock speed, as you can have more aggressive latency timings. And comparing RAM speed of 667 to 800 is not that big of a difference in performance (maybe a few fps in games), but that's about it. Your biggest bottlenecks are your CPU and graphics card.

The Conroes are running at lower clock speed then they are capable and have plenty of headspace for overclocking. You should have no problem with 3.0-3.2 GHz with a E6600 at stock voltages and still maintain temperatures that are lower than the Athlon 64 X2 processors. I'm not sure why you would want to stop at 2.6GHz as you probably won't notice any significant difference.

I'm currently running P5W deluxe mobo + EVGA 8800GTX + Corsair XMS2 DDR2 800 (6400C4) + E6600 running at 3.0GHz (333MHz x 9) stock voltage and the RAM running at 667 (Using Zalman 9700 HSF) and it's been running Vista Ultimate 64-bit edition w/o a hitch.

Velocity666, as mainyard stated, RAM are double pumped (hence dual channel) and FSB are quad pumped. So to get the RAM speed you multiply the bus speed by 2, to get the FSB speed, you multiply the bus by 4, and to get the CPU speed you multiply the bus speed by the multiplier.
March 12, 2007 1:19:22 PM

Sorry if someone's already mentioned this, but if you underclocked your RAM you could tighten the timings.
March 12, 2007 10:59:47 PM

Quote:
Is it possible to overclock the cpu to say 2.7Ghz and manually set the ram to back to 800 or would it automatically overclock the ram again?

It all depends on the MB (and its BIOS). Some MBs have you specify the RAM speed separately from the FSB and automatically adjust the FSB:RAM ratio to keep the RAM speed (almost) unchanged when you change the FSB speed. Others have you specify the ratio directly (or indirectly) and keep the ratio the same when the FSB speed is changed.

Here's an article with test results on the performance differences between running differing speeds/timings of RAM on C2D system:
http://www.madshrimps.be/?action=getarticle&number=1&ar...
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