Overclock advice wanted: Which first, multiplier or FSB?

Hi all,

I managed to resist the lure of Sandy Bridge and Ivy Bridge and remained somewhat content with my Core 2 Duo E8500 (overclocked to 4.2GHz). Lately, however, I become a bit unhappy with my gaming performance and bought a Core 2 Quad Extreme QX9650. Yes, I know that it's "obsolete" but it was the cheapest "upgrade" I could perform while awaiting the release and reviews of Haswell.

Currently it's running at 3.33GHz (333x10) as I only changed the multiplier but not the voltages. This works great and the quad core has given a real boost to those games that are optimized for multiple cores. I see much better performance in Far Cry 3 and Borderlands 2, for example. But, I see a decrease in performance in Torchlight II as it's not optimized for multiple threads. In a large battle I'll see the frame rate drop to 7fps. Yep, that's right, single digit, 7.

I've read quite a bit on the Overclocking websites (some of it contradictory) so my question is in what order should I be experimenting? Should I go for maximum FSB first or maximum multiplier? On the E8500 I had no choice, it had to be FSB and I really think that I just lucked into a good, stable overclock. I'm leaning towards the FSB maximization as that should give me an overall system boost but I'm just not sure if that's the right way to go.

I need some guidance from the experienced hands.

Well, a Multi OC will OC the CPU and leave everything else alone.
FSB OC will OC CPU/RAM together. But you'll have to bear in mind, you need to slow the RAM way down before starting a FSB OC and tweak it last.

You'll get better overall numbers from a FSB OC. But theres nothing wrong with a Multi OC either. Really depends on how you want to do it and your other hardwares capabilities.

Personally, I would do a FSB OC.
Depending on how far you want to go ... a 400FSB should be pretty easy depending on your board.

But if you want to see just what it can do, reset everything back to default.
Then, set your CPU multiplier as low as it will go (x6 I think)
Then, set the RAM as slow as it will go.


Form this point, you want to start raising your FSB a little at a time untill you BSOD at start up.
This will be your FSB limit at the Nb voltage. Now you can try to raise it a bit, but I would just see how high you can get it with stock voltage. You may need to raise the NB voltage later a touch to stabilize once everything else is at full speed.

Once you know what your FSB wall is, (lets just say it was 425) youll know your NB limits.
What I would is drop a bit below the last FSB that was somewhat stable. (I/e booted to Windows at 420, but BSOD at 425 -- I would start at say 390 or 400 which should be in a safe stable range.)

Then start bumping the CPU multiplier back up 1 at a time and check for stability (Leave RAM alone for now but make not what speed its at)

I would also try to keep the RAM as close to its rated speed as possible. This may mean having it set a 667 speed in bios, but will be running at 800 or better after CPU/FSB OC.


2 DIMMs slots will be easier to OC than all 4 full too. If all 4 are full, more stress on the NB will mean less of an OC.

As for max safe air levels/BIOS settings:

Vcore actual 1.3625v (Use CPU-Z to montor clock speed/cpu voltage(vcore) )

Core Temps, keep below 80c (90c max) when stress testing.

NB voltage 1.4v (around 1.25 to 1.3v should be sufficient. This setting is important when dialing in the RAM after the CPU OC)

LLC = Enabled (Load Line Calibration. When you input your vcore manually in the BIOS, it will report differently in Windows. Especially under load. This is known as vdrop or voltage drop. If the voltage drops too low, instability follows.

Disable Speedstep/C1E (Unlike Sandy onwards, 775 socket does not like speedstep and Overclocks.)


With that chip, 3.6Ghz should be a giggle. 3.8ghz - 4ghz chip dependent.

Thanks, Wishmaster and smarteyeball.

I'll report back with my results!

Thanks smarteyeball. Thats very usefull info I probably should have included :)


Lava King, please also keep in mind that your load temps will trump all. Dont just set it at the highest safest rated voltages.
Although Smarteyeballs numbers are accurate, they are also the highest you can go safely. After that its considered a gamble.
Alot depends on your hardware. (Cooling setup etc)
So you may not be able to exceed say , 1.28Vcore or 1.3 without going into the danger zone on temps (Over 80C under stress). In which case that would be YOUR Max.

Watch those temps 1st and foremost and make sure you stay at or below those recommended voltages.


It will take some time, and a lot of stress testing but can be fun too. Let us know what you come up with. :)

Oh, and for a final stress test ... I would recommend a good 11hr run of Prime. If it gets past that after your done tweaking, your golden!

Wishmaster said:

Although Smarteyeballs numbers are accurate, they are also the highest you can go safely.

Definitely. A simple thumb rule to overclocking is the lower the better when it comes to both voltages and temps.

If you can use less voltage for a desired clock speed, do it :)

And also correct is that each chip hits it's 'comfortable' point with temps and required volts.

(I had a Q9550 that would not stably budge past 3.79Ghz. 100mhz extra for 3.8ghz required a silly jump in vcore required to keep it stable. Added another 10c to temps too iirc. Not worth it.)


Here is a few main apps we use for monitoring temps and voltages and stress testing:

Core Temp

CPU-Z (CPU vcore/voltage monitoring)

Prime95 (Torture Test/Blend 8-12 hours)


There are other temp/monitor apps like speedfan, real temp, Hwinfo. it's personal preference really.

LinX/OCCT/Lin Pack/IBT (intel burntest) These are a few stress apps based on the same binaries. The only major difference is the GUI. These tests are for your 'quick and dirty' vcore tests. Pass 10 tests and you know you're on the right track. Be careful though, these apps will add up to 10c over Prime95. Never in real world usage will you hit these temps again though.

Here are some preliminary results:

The CPU will not clock to 3.4GHz no matter what (high Multi and low FSB, low Multi and high FSB).

At 3.4GHz it won't pass IBT standard test, it gets an error within 10 minutes on a random core. At 3.375GHz it passes the IBT standard test (10 iterations) and ran Prime95 for 4 hours.

The FSB wall seems to be 470MHz with Vcore actual at 1.36v, Northbridge at 1.3 and ram at 2.0v (Kingston specifies 2.3v as max, didn't see a need to push it that hard). Multi at 7.0 (3.29GHz) works, 7.5 (3.525MHz) does not.

With the FSB set to 333MHz and voltages same as above, Multi at 10 (3.33MHz) works, 10.5 (3.496MHz) does not.

The Prime95 4-hour test mentioned above was run with FSB at 450MHz and the Multi at 7.5 (3.375MHz). Just got finished playing Torchlight 2 online with a friend (4.5 hours) without a problem.

I've tried the FSB in non-multiples of 5 but 3.4GHz is a no go.

Perhaps some of the more esoteric settings in BIOS would help, but I don't want to delve into it that deeply.

Overall performance is much better than the overclocked E8500, so I'll happily play on this setup until Haswell comes out.

Oh, temps were never an issue (not at these speeds). After the 4 hour Prime95 run, the max CPU temp was 60C (I think, perhaps it was a bit higher).

I'm going to run a longer Prime95 test, but foul weather is moving into the area (same storm that just went through Oklahoma City) so I'll have to put it off until later.

Thanks again for the help, guys.

I'll probably experiment on lowering the voltages, too.

Uh oh, tornado warning siren going off, better see what's happening.

3.4Ghz is a low speed to get into trouble. Especially with those volts. You will have to adjust at least one more BIOs setting.


C.I.A.2 = Disabled


(and did you enable LLC, disable Speedstep etc? )

As for the RAM, what's it reported as @ 3.3X in mhz?

To make sure RAM's not an issue, set the:

CPU Host Frequency (Mhz) = 200

It can be readjusted later.

smarteyeball said:

3.4Ghz is a low speed to get into trouble. Especially with those volts. You will have to adjust at least one more BIOs setting.


C.I.A.2 = Disabled


(and did you enable LLC, disable Speedstep etc? )

As for the RAM, what's it reported as @ 3.3X in mhz?

To make sure RAM's not an issue, set the:

CPU Host Frequency (Mhz) = 200

It can be readjusted later.

C.I.A.2 and Speedstep were disabled and LLC enabled before beginning this adventure. :)

Sorry, not following you about the RAM, the picture shows what I have to work with. I was assuming that CPU Host Frequency = FSB in this case.

The memory frequency shown in the picture is as low as I can get it with the available settings.

Perhaps it's just one of those things, and this chip won't OC reliably.

Thanks for taking the time to help!

Where is the front side bus readout for this motherboard ? Am I just missing it ?

1333 MHz ?

http://www.gigabyte.us/products/prod...px?pid=3013#sp