overclocking my cpu from 2.1 to 2.8 why is my ram at 867

[Xarick]

I have 3 gigs of ddr2 800. I OC my e6400 to 2.8ghz by adjusting the fsb. Now my ram is running at 867. Why is that? I thought it would stay at 800?

 

[imported_wired247]

check a bios setting called FSB strap to northbridge. changing it allows different RAM speeds (dividers)

 

[Xarick]

it is on auto.

 

[krnmastersgt]

Well if you want it to stay at the stock 800, you'll need to change it manually. What's your current FSB and multiplier for your CPU?

 

[mpilchfamily]

With it on auto the RAM speed will go up in proportion to the FSB.

 

[Xarick]

is that good or bad? Would it be better if I forced it down to 800?

 

[imported_wired247]

for best stability I'd keep ram at its rated settings.

 

[Xarick]

so should I set it to 200 then?

 

[CoinOperatedBoy]

Try running memtest86+ for several hours with your current configuration. If you're stable at 867, then leave it. It's a modest overclock. You could even increase your Vdimm slightly if you get errors. If you're not comfortable with that, then yes, set the RAM to run at stock. That may mean setting it to 400; it may be BIOS-dependent.

 

[magreen]

Your FSB is currently ~350 (or 1400 if we're using quad-pumped lingo), and your multiplier is 8, giving you 2.8GHz on your e6400. Your ram:fsb ratio is set to 5:4, meaning that at the stock 266 speed of your FSB (1066 in quad lingo) your ram would be running at ddr-667 speeds. (That's because the ram would be running at 266*1.25=333 which is called ddr2-667 speed since ddr is double-pumped).

You OC'd your cpu to 2.78GHz, which is 347 FSB * 8, so your ram is running at 347*1.25=434 MHz, which is ddr2-867 speed.

Your ram is rated for a maximum speed of 400MHz or ddr2-800 speed. I'd recommend keeping it to that, since OC'ing the ram on a c2d system doesn't improve system performance anyway. So all you need to do is adjust your ram:fsb ratio to 1:1 and you're golden to raise the fsb all the way to 400MHz for a 3.2GHz OC on the cpu. Different motherboard bioses call the ram:fsb different things. Some call it choosing "ddr2-533 speed" since that's the natural speed your ram would run at if it were 1:1 and you didn't OC the fsb. Others call it 1:1. I think gigabyte boards screw with your head and call it 2:1 since they're talking about the double-pumped ddr2 speed (i.e. 266fsb=ddr2-533 speed).

Clear?

 

[Xarick]

I am wrong it is 876 not 867
Your right that my fsb is at 350. I wasn't able to push it much beyond that until it wouldn't boot. I think my highest was 2.88ghz.

so right now in auto my ram is running 350 right? so right now with it in auto I am in 1:1 so it is right where it should be.. correct?

 

[magreen]

Ok, 876 makes more sense with the 2.8GHz you reported. So that's 350 fsb.

Now, that means your ram is actually running at 438MHz, which is 38 MHz faster than its rated speed (again, ddr and ddr2 speed refers to effective speed and is double the actual clock frequency of the ram). That's why you're hitting a wall in overclocking.

And no, at auto it is not running at 1:1. It's running at 5:4, hence 438:350. You need to set the ratio to 1:1 and you will find you can magically OC your cpu much higher -- I would expect you to have no trouble hitting 3.2GHz, maybe 3.3 or 3.4.

 

[Xarick]

Okay my board is not allowing me to make that setting.
I have the fsb strap setting gives me 200, 266, 33 and 400
Then the manual timings are derivatives of that. 876, 841, 700 something etc.

So what should I be setting this thingy at.
I am a bit confused though because I got ddr2 800 because I was told it could run up wto 1600mhz.
ddr2 667 was used for a 1066 fsb and ddr2 533 was used for an 800 mhz fsb. So where am I lost here?

OH WAIT! DING Lightbulb!

What you are saying is I should set the strap to 400 and then the manual timings to 700.
That gives me a ddr2 frequency of 350 hence matching my FSB!
Thus I can boost my FSB to 400 and it will force my manual timing up to 800 and thus give me 1:1! Syncronis!

 

[magreen]

Now you've got it! :thumbsup:

 

[Xarick]

Thanks magreen a couple more questions. I don't really want to push to 3.2 at this time because I want better cooling and think I may have to adjust voltage cause it won't boot on 3.2. I am pretty happy with 2.8. Both a strap of 333 and a strap of 400 give me the option of 700. Which would be better and why?

Also is it better to run 1:1 or should I run at 848. Or is it bad to have your memory running faster than rated?

 

[CoinOperatedBoy]

Set as low a strap as possible. My understanding is that higher straps loosen northbridge latencies for stability at higher speeds. Given the option to run RAM at the same speed at two different straps, you should choose the lower because performance will be slightly worse at the higher strap, unless stability is affected.

There's nothing "bad" about running faster than rated except that your performance is not guaranteed by the manufacturer and you will have to do some testing to make sure you're stable at that speed. Most RAM should be able to run 50MHz higher than rated, possibly even at stock timings and voltage. Personally, I would run the RAM at 848 instead of 700, even if it means not running 1:1 with the CPU. However, you should make an effort to get a good cooling solution and hit 400FSB so this isn't even a concern.

 

[magreen]

When you say it won't boot at 3.2 and you'd have to adjust your voltage to hit that speed, that was before you had set your memory to 1:1, correct?

So of course it wouldn't boot at 3.2, not because your cpu was too hot, but because you were overclocking the bejesus out of your ram. Think about it -- 3.2GHz means 400 fsb * 8, and with a 5:4 memory:fsb multiplier you were attempting to run your ram at ddr2-1000 (500 MHz) speed. Of course it wouldn't boot (unless you had some uber ram, but then you'd have had to run some uber voltage thru it :lightbulb.

Now that you know how to set the ram to 1:1 with the fsb (i.e. "700" with your current 2.8Ghz OC), you can hit 3.2GHz without overclocking your memory one drop. That's what I was trying to tell you b4. I think it's likely to be stable without raising the voltage.

As far as which strap, that's right, higher strap means higher latencies, so you want the lowest strap that allows you to overclock the cpu to your desired frequency stably.

What motherboard are you using, and what chipset does it have?

 

[Xarick]

p5q se
I tried running 1 to 1 at 400 and I just get a black screen. It then errors and says overclock failed.

 

[magreen]

Ah, ok. Maybe it is a heat or voltage issue. You could try pushing up slowly from 2.8 if you want. And there's no harm in raising the voltage slightly, even if you're using the stock cooler. Or you could leave it if you're happy with it.

If you do leave it at 2.8GHz, I'd recommend running your mem at ddr2-700 and not 876. You'd just be introducing instability into your system by running your mem out of spec, and you don't get any real-world benefit out of faster memory speeds with a core 2 duo system.

 

[CoinOperatedBoy]

OP -- have you raised Vcore at all? I would think that chip could at least boot at 400MHz FSB, but maybe not. My E6600 won't.

Real world, I agree, little noticeable difference when comparing 700 vs. 800-900. But why not try it out and see if it's stable? It doesn't take much effort to run memtest overnight. And run a benchmark or two to compare scores at both speeds. If latencies remain the same and voltage stays put or goes up only slightly, why not take the higher result? At least if you're stuck at this FSB.

 

[Xarick]

I have not messed with the vcore.

 

[imported_wired247]

the standard procedure of overclocking (LGA775 intel cpu)

- ensure adequate cooling for motherboard and CPU
- loosen RAM timings
- raise FSB (and/or possibly CPU multiplier)
- raise vcore / vMCH / VTT / PLL etc to their necessary levels
- after all else is stable, find your best stable settings for RAM

If you ignore the adequate cooling or raising the required voltages you won't have a successful overclock.

raise the voltages too much and cooling will fail or you won't even be able to boot / POST.

mess with the RAM before you get your CPU stable and you could fail at overclocking as well.


lots of help available in CPU/overclocking forum, but right now it sounds like you shouldn't be messing with it too much without doing more research