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Underclocking for reliability

K

KamalS

Junior Member
Currently my FSB is running at 1333MHz.

The CPU is a Q8400 and the RAM is a PC6400 TWINX that runs at 400MHz.

From what I know, in the current scenario, the CPU is doing a lot of wait cycles on the slower RAM.

The RAM being of the "economy/value select" type, I am not going to increase it's clock.

That leaves me with underclocking the CPU to match the RAM freq.

I believe this should make my system more stable ( atleast compared to overclocking ) and have a little more life than before?

What freq. should I set the FSB at and how should I do it ( I have the GA-P45-UD3P motherboard )

What I am loking at is hardware stability and the longest possible life from my hardware
 
Your ram is actually running faster than it needs to be...
FSB is quad pumped so its really 266mhz. Which makes your ram rated up to 1600FSB
 
I think Kamals is looking at things the wrong way. And I suggest a read of the recent Kenmitch threads regarding the E5200 processor.

We can maybe assume that an underclock will reduce CPU heat and therefore increase CPU life expectantsy. But is that true across the board and is it a simple curve or a curvilinear relationship?

I submit not when Kenmich has demonstrated it very possible to increase overclocking speed by reducing vcore below stock settings, while increasing cpu speed at the same time. Overall CPU temperatures are thus reduced while speed increases, so why should the CPU not last longer than stock settings?

Maybe the too greedy overclocker can play the fools game of increasing vcore to the max, they may get excellent speed, but where are they if they burn out their CPU?
 
Saving energy is my main concern.

Just next to it, is longevity.

I guess that if I sync my CPU with the RAM, then the CPU would not be burning idle cycles waiting for the RAM to respond - is this assumption of mine incorrect?

I read this thread : http://forums.anandtech.com/showthread.php?t=321110

It seems like it is possible to reduce voltages while keeping the CPU running ATLEAST at stock speed and more.

What I want to do is this:

1. Keep the RAM and CPU in sync ( I want to minimize the idle cycles of the CPU vs RAM )
2. At the same time, get the stock CPU freq although the FSB is now changed.

So maybe this is what I want to do:

1. 1333Mhz FSB == 333.25 core speed ( FSB is quad pumped )
RAM is rated at 400MHz core ( 800MHz, DDR - Dual Channel )

This means that I need to increase my FSB to 400MHz for the CPU and RAM to match?

2. So I need to set my FSB to 1600Mhz ( 400 * 4 ) for CPU and RAM speeds to match?

3. This would automagically overclock my CPU from stock 2.66 GHz = 2660Mhz to ( ( 2660 / 1333 ) * 1600 ) = 3193Mhz = 3.19GHz. Right?

4. This overclocking however would increase the power consumption as well, so I can keep temperatures down by decreasing the vcore?

Would this be a good idea?

5. Or should I reduce the multiplier ( or mutiplier settings have nothing to do with reducing power consumption? )
 
Read some of the stickies on overclocking before diving in.

You may not be able to both up your FSB and drop your vcore and still have a stable system.
 
Heya,

I'm not really sure what you're trying to accomplish, but I'll try and give you some ideas. I underclock CPU's on purpose too. I overclock my main system, but my HTPC and Server are undervolts & underclocks. Yes, it uses a tiny, tiny, tiny bit less energy when you lower the vCore. It's very small though. It's not worth instability when you realize that you may underclock your CPU and see no wattage draw difference because the motherboard itself draws so much depending on its make and what's going on.

Underclocking will not increase the life span of your CPU in a meaningful way. Undervolting can increase life span theoretically but consider that by the time the CPU is old enough for you to see that `hidden gain' by undervolting, the CPU would be so old, you'd be reading about it as very, very old tech on some `classic' website about the history of CPU's. Don't worry about this. You're not gaining some kind of hidden extra life on the CPU. You're more likely to change it out long before you ever see a gain in life span.

I undervolt my Server & HTPC as well as then underclock the CPU. The point being to lower the heat and power via undervolting, and then lower the clock (underclock) so that the chip isn't strained at the new lower voltage setting. I do this so that I can then passively cool the CPU without a fan, without risking high temps on the CPU. And I do that to be fanless because fanless = silent, and I want quiet on my HTPC. On my server, I do it to have less power draw and cooler temps (fans take energy to work, so fanless = more power saved, on top of it being undervolted and using less power) as I leave it on 24/7, every watt matters to me there.

I would not change the base settings and worry about idle cycles concerning your FSB, CPU and RAM. Especially since saving energy is your primary concern as you stated.

If you want to save energy, as that is your primary concern that you wrote, you can undervolt the CPU and then slightly underclock it and slap a huge passive heatsink on it (mugen 2 comes to mind) so that you can go fanless and use even less power. Less CPU power, no fan power used. Then use low power components for the rest of the system. Get a high efficiency rated PSU with a lower wattage rating so that your expected wattage usage measures to be between 50% and 80% of the PSU's wattage rating to get closer to that efficiency rating (using 5% of the potential wattage output of a 1,000watt PSU for example is actually more wasteful than keeping a 350watt PSU loaded at 200 watts or so). That said, my server sits around 47 watts, so it's hard to get a PSU that is low enough to meet what I'm talking about. For a machine meant to do more, a higher PSU is going to be used of course.

-- What's the nature of the machine's use here?
-- Is energy use a concern due to budget of the electricity bill?
-- Are we talking 24/7 use? Or just on when used?
-- Why are you concerned with life span of a CPU that you're not overclocking?

Very best, 🙂
 
FSB going higher than stock is a bad thing for stability, always. You're pretty much overlcocking your motherboard when you do this and they aren't made for pushing mhz, while CPU's are specifically designed for such ventures.

Don't think in terms of mhz when it comes to your memory, think bandwidth. DDR 2 at those speeds is sufficient and these wait cycles should NOT be prevalent with that setup like you say they are.

You're underestimating your memory configuration.
 
I don't think longevity is a real issue. I mean at stock the processor could be expected to run for 10 years. You might be able to get it to 15 years but who runs their computers for 15 years? By then the power of your current PC will be offered as a wall wart.
 
u undervolt for longivity / lower heat values.

You overvolt for stability / problem free.

Example... if your running stock GHZ... downvolted to 1.10 instead of 1.25.... should u have some kind of voltage, you can lose your clock because your cpu will not get the required amps.
vs.
stock GHZ @ 1.325V vs 1.25. Same scenario, however since u have more voltage, a voltage dip would do almost nothing.

However if you overvolt too much, you will damage your chip due to electron migration.

So its a toss card in the example you given.

Its far easier to get a better sink and try to lower your temps 10C to double your life... vs try to play with voltage, and reduce it 10C.

You'd get better gains on the aftermarket sink, depending on processor.

Now if ur using a dinky dualcore, no sink will help you unless your already in extreme OC.
 
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What aigomorla say's above is all totally correct... I would add that a a good power supply would help avoid the possible crashes from power fluctuation.

I will never forget seeing an office full of Dell PCs reboot when the power was cut momentarily, while my self built machine with a Tagan power supply carried on burning a CD. The system in question was slightly overclocked but was volted only @0.05v higher than was needed to be stable at that frequency.
 
Well, silly of me NOT to provide some important details like my motherboard and SMPS configuration.

My motherboard is a "good" one : Gigabyte GA-EP45-UD3P. This is overclocker friendly.

My CPU is a Q8400 - is it not "overclocker friendly" as well? ( atleast the little bit I am talking about? )

My SMPS is an Antec EarthWatts EA650 - might not be the best, but can supply enough juice for some mild overclocking.

I have the stock fan + headsink that came in the Intel retail CPU box.

Would it be not recommended to change the FSB from 1333Mhz to 1600Mhz if I want my system to last a good 8 - 9 years?

My RAM is rated good till PC6400 and as it looks like the CPU and MB is built for some overclocking, if life would not be an issue, I would like to run the whole thing @400MHz core clock.
 
Scholzpdx said:
Fixed, but it still makes sense.
Click to expand...

I am not sure I follow the calculations.

My TWINX is spec'ed till PC6400 - this should allow me to run it at spec @400MHz core.

On a "quad pumped" FSB - should this not be 1600MHz?

In that case, how is my RAM running faster than it needs to be when the stock FSB ( current settings ) is 1333Mhz?
 
KamalS said:
I am not sure I follow the calculations.

My TWINX is spec'ed till PC6400 - this should allow me to run it at spec @400MHz core.

On a "quad pumped" FSB - should this not be 1600MHz?

In that case, how is my RAM running faster than it needs to be when the stock FSB ( current settings ) is 1333Mhz?
Click to expand...

http://forums.anandtech.com/showthread.php?t=47089

FSB: 333
RAM:400

Your ram is running faster than your FSB, which is good. If you need more reliability your going to need ECC ram. If you need longest possibly life i recommend feeding it liquid hydrogen coolant and placing it in a solid gold box to prevent cosmic radiation
 
Ben90 said:
FSB: 333
RAM:400

Your ram is running faster than your FSB, which is good.
Click to expand...

Ram running faster than your FSB has very little if any benefit, especially in terms of stability.

Ben90 said:
If you need more reliability your going to need ECC ram.
Click to expand...

Intel server board chipsets stopped using ECC ram a while ago (2 years?), I think the last one was the x38, but I guess if you're really good with a rotory tool...
 
Schmide said:
Ram running faster than your FSB has very little if any benefit, especially in terms of stability.



Intel server board chipsets stopped using ECC ram a while ago (2 years?), I think the last one was the x38, but I guess if you're really good with a rotory tool...
Click to expand...

I got registered and ECC ram confused 🙁. If you absolutely need all the stability possible, you should look into registered RAM, but i doubt it matters for OPs application.
 
Schmide said:
Ram running faster than your FSB has very little if any benefit, especially in terms of stability.
Click to expand...

You guys mean to say that the RAM is running @ 400Mhz although the FSB is running at 333Mhz?

The RAM has a clock different from the FSB?

Is not the RAM clock derived from the FSB and both "core freq" are the same ( If FSB is running @ 333MHz, then RAM is automatically running at 333MHz core -> 2 * 333MHz DDR rates )

Or am I wrong?
 
KamalS said:
You guys mean to say that the RAM is running @ 400Mhz although the FSB is running at 333Mhz?

The RAM has a clock different from the FSB?

Is not the RAM clock derived from the FSB and both "core freq" are the same ( If FSB is running @ 333MHz, then RAM is automatically running at 333MHz core -> 2 * 333MHz DDR rates )

Or am I wrong?
Click to expand...

The ram freq is derived from the FSB clock, however you can set a memory divider other than 1:1 to achive different ram clock speeds. In you scenario its a 5:6 ratio.
 
F1shF4t said:
The ram freq is derived from the FSB clock, however you can set a memory divider other than 1:1 to achive different ram clock speeds. In you scenario its a 5:6 ratio.
Click to expand...

What this means is every 5 CPU bus cycles the RAM is running 6.

OP-- you do not need to worry about wearing out your CPU. It will last for 10 years.
If you wanted to you could run the RAM at a 1:1 ratio, this will clock it at DDR2-666 running it at 666mhz instead of 800mhz. You set this in the BIOS. But this would not make a difference in the longevity of the RAM either.

What you could do is run your RAM at 1:1 and overclock the CPU to be running at 400Mhz FSB. Voltage+heat terminates a CPU long before anything else. My guess is you could run your CPU at 7*400mhz without a voltage increase.
 
If you want to save energy, one important area to consider is PSU.

I've seen reviews of 500W PSU comparisons where the difference between less efficient one to the best one is as huge as 100W.
 
My guess is that you could drop your VCORE, but your Northbridge voltage is going to likely have to go up to support 400+ FSB, as may your memory voltages and other settings.
To undervolt, I would start by seeing what voltages can be reduced running chip and board at full defaults. Compare case and CPU temperatures at stock vs. the reduced voltage. Then start raising FSB with Northbridge voltage increase only (depending on your motherboard there will be other voltages to tweak) and watch the temperatures as the speed goes up, and try to find an operating setup that you are happy with.

Forget about the "target" that you had in mind for an overclock/undervolt when you assembled the setup.
There is a "sweet spot" for any chip, and your task is to find it.
 
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There's some scenarios that are beneficial when the RAM is running at a higher rate than the FSB, like memory copy operations and overall bandwidth efficiency, but still, the FSB is the limiting factor.
 
The OP states "What I am loking at is hardware stability and the longest possible life from my hardware".

Set all of your system settings to auto. Move on. Seriously, the machine will not last a day longer because of anything you can do better than the stock settings and it's highly unlikely the machine will even be usable in any meaningful way long before the life span of the machine is up running at stock settings...
 
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