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I5 750 to 4GHZ on air - Gigabyte P55 series

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April 18, 2010 6:17:21 PM

Right I've spent ages scowering Google and multiple forums and there's no definitive how to. Other than "research i7 over clocking - it's the same!" hard information is hard to come by without here and there searching.

So while this isn't a definitive how to guide, it should at least be of some help as I aim to get all that info into one place!

I'm not a wizard of over clocking by any means and in fact rely way too much on motherboard safety features. I am human afterall, and it's saved my DDR3 RAM from being over clocked from 1.6GHZ to 2.0GHZ because Id forgot to re adjust a multiplier.

This isn't an over clocking for dummies guide, more of a beginner-intermediate level

Right, time for some history!

Overclocking was previously done by pushing your CPU harder using the front side bus frequency. The front side bus (FSB) being a chip that connects all of the components in your PC together. The RAM, graphics card, CPU are all connected by this.

In laymans terms. The CPU does the 'thinking', the FSB does the connecting.

In later systems (and now Im talking about my old AMD AM2 64 with an Asrock mobo) you could offset - or asynchronously over clock the FSB without over clocking the graphics card.

Why am I mentioning this? Because the newer architecture takes this idea to the next level.

You have a base clock - or what could be called the FSB
A RAM multiplier - take the base clock, multiply this = your RAM speed MHZ
A CPU multiplier - take the base clock, multiply this = your CPU speed in MHZ

So Ill be basing this guide on the Gigabyte GA-P55M-UD Rev 1.1 F8 Bios motherboard

I will mention Foxconn sockets at this point. From the information I could find - burned out sockets were occurring on R1.0 boards even without over clocking. I personally haven't had this problem and put it down to the Rev 1.1 being a modified socket, despite Foxconn claiming "under normal use will work fine"

But I digress, this isn't a thread about Foxconn so on with those settings.

The DEFAULTS :

Ok so each motherboard will vary so you'll want the book to hand to find exactly how to access each setting. This is an overview of settings, not an idiots guide - remember...

CPU clocks:

Base clock (BCLK) : 133MHZ (Control disabled)
QPI Clock ratio : ??x (Auto) - CPUz sometimes implies 28X despite only 32x or 36x settings being user selectable
RAM multipler : 10.0 (Auto)
CPU Clock ratio : 20.0 (Auto)
PCI Express : 100MHZ (Auto)

Advanced CPU tech:

Intel boost tech : Auto
CPU Cores enable : ALL
CPU Enhance Halt (C1E): Auto
C3/C6/C7 state support : Auto
CPU Themral Monitor : Auto
CPU EIST : Auto
Bi-Directional Prochot : Auto

RAM settings:

XMP : Disabled
System memory multiplier : Auto (LINKED TO CPU --> RAM multiplier - changing one changes the other!)
Channel A Timining settings -->
Should all be greyed out (Auto)

---ON TO OVERCLOCKING!---
a b K Overclocking
April 19, 2010 1:14:27 AM

Thanks for the info
April 19, 2010 10:56:18 AM

My final post:

Right I've spent ages scowering Google and multiple forums and there's no definitive how to. Other than "research i7 over clocking - it's the same!" hard information is hard to come by without here and there searching.

So while this isn't a definitive how to guide, it should at least be of some help as I aim to get all that info into one place!

DISCLAIMER! I WILL NOT be held accountable for burnt out hardware or poor performance / loss of work - you the the idea. This is a guide, not an instruction book!

I'm not a wizard of over clocking by any means and in fact rely way too much on motherboard safety features. I am human after all, and it's saved my DDR3 RAM from being over clocked from 1.6GHZ to 2.0GHZ because Id forgot to re adjust a multiplier.

This isn't an over clocking for dummies guide, more of a beginner-intermediate level

Right, time for some history!

Overclocking was previously done by pushing your CPU harder using the front side bus frequency. The front side bus (FSB) being a chip that connects all of the components in your PC together. The RAM, graphics card, CPU are all connected by this.

In laymans terms - the CPU does the 'thinking', the FSB does the connecting / movind data about.

In later systems (and now Im talking about my old AMD AM2 64 with an Asrock mobo) you could offset - or asynchronously over clock the FSB without over clocking the graphics card.

Why am I mentioning this? Because the newer architecture takes this idea to the next level.

You have a base clock - or what could be called the FSB
A RAM multiplier - take the base clock, multiply this = your RAM speed MHZ
A CPU multiplier - take the base clock, multiply this = your CPU speed in MHZ

So Ill be basing this guide on the Gigabyte GA-P55M-UD Rev 1.1 F8 Bios motherboard

I will mention Foxconn sockets at this point. From the information I could find - burned out sockets were occurring on R1.0 boards even without over clocking. I personally haven't had this problem and put it down to the Rev 1.1 being a modified socket, despite Foxconn claiming "under normal use will work fine"

But I digress, this isn't a thread about Foxconn so on with those settings.

I will start by saying - some users have complained about stuck restarting systems - make sure your RAM is in the right slot (slot 1)

On my board the arrangement top to bottom was 2-1-4-3 so be careful!

The DEFAULTS :

Ok so each motherboard will vary so you'll want the book to hand to find exactly how to access each setting. This is an overview of settings, not an idiots guide - remember...

CPU clocks:

Base clock (BCLK) : 133MHZ (Control disabled)
QPI Clock ratio : ??x (Auto) - CPUz sometimes implies 28X despite only 32x or 36x settings being user selectable
RAM multipler : 10.0 (Auto)
CPU Clock ratio : 20.0 (Auto)
PCI Express : 100MHZ (Auto)

Advanced CPU tech:

Intel boost tech : Auto
CPU Cores enable : ALL
CPU Enhance Halt (C1E): Auto
C3/C6/C7 state support : Auto
CPU Themral Monitor : Auto
CPU EIST : Auto
Bi-Directional Prochot : Auto

RAM settings:

XMP : Disabled
System memory multiplier : Auto (LINKED TO CPU --> RAM multiplier - changing one changes the other!)
Performance Enhance : Turbo
DRAM timing selectable : Auto
Channel A Timing settings -->
Should all be greyed out (Auto)

Voltages :

All are Auto

---ON TO OVERCLOCKING!---

Id suggest at first get that RAM up to full spec.

Gigabyte boards have a habit of terribly underclocking your RAM. You can overclock your RAM - I didn't. But we do want it at stock at minimum - so - go find the spec sheet for YOUR RAM - this will be on the manufacturers website.

As a comparison, my 1600MHZ 7-8-7-24-2T / 1.6V was running at 1333MHZ 9-9-9-24-1T / 1.5V

So change those settings first.

Back on RAM change

Performance Enhance : Standard
DRAM timing selectable : Enabled
Channel A Timing settings -->

From your spec you should have a number like mine - something like 8-8-8-24-2T or maybe 8-8-8-24-2N (these are the same!) or even 8-8-8-24 - that's fine.

The 4 numbers you have are CAS Latency Time, tRCD, tRP. tRAS and - if you do have the 2N or 2T or the like - that's Command Rate (CMD)

So go ahead and make the changes - bringing the RAM turnaround timings up to spec. Leave everything else at Auto!

Next we probably need to change that RAM voltage

Go into Advanced voltage settings and change the DRAM Voltage to the voltage of your RAM.

Now we have the RAM at recommended timings and recommended volts.

Now a likely question at this point will be "that's all well and good, but my RAM isn't running at stock frequency"

Unless yours ISNT 1333MHZ RAM, you can skip the next part up to memtest

Now comes the overclock. Take your RAM advertised speed (so 1600MHZ in my instance) and divide it by 10

So I get 160

You now need to change your base block to that frequency.

So change Base Clock control to enable
And change the BCLK frequency to whatever you calculated

Now, it's likely your CPU has been overclocked with it - we don't want this to happen quite yet so lower the ratio until the CPU sits just under 2660MHZ or 2.66GHZ

For a more scientific way, do 2660 / Your calculated BCLK and ROUND DOWN - this gives you your CPU multiplier.

If you wanted a stock CPU and full speed RAM you could just stop there as that's what your system will now be running.

1333MHZ RAM readers should start reading again now - you need to test that RAM before we carry on. If the system hangs or isn't stable - the RAM can be the most likely of culprits - PSUs aside - so we test that first before any OCing and make sure its all working OK and within an acceptable failure rate (NO RAM is perfect - ALL sticks have defects, it's how many of these occur that can ruin a system)

Save everything to the BIOS and keep reading

Once we've done memtest - we get onto the REAL OCing - if not - you have dud RAM and continuing with broken RAM will only cause you more problems than it's worth!

So your RAM works - great.

Back to advanced CPU tech :

Intel boost tech : DISABLED
CPU Cores enable : ALL
CPU Enhance Halt (C1E): DISABLED
C3/C6/C7 state support : DISABLED
CPU Themral Monitor : Auto
CPU EIST : DISABLED
Bi-Directional Prochot : Auto

This prevents your system from trying to 'slow down' or interfere with your over clocking efforts. Keep the thermal monitor enabled - it's a safety thing that will throttle the CPU if it gets too hot.

Speaking of heat - I hope you have a good cooler. I personally am using a Hyper 212 Plus and a Zalman ZF-3 extra fan. Its moderately priced for a cooler and offers decent performance for the price (a reason why you probably bought an i5 to start with)

RAM settings:

Performance Enhance : STANDARD
DRAM timing selectable : ENABLED (since we change settings earlier)
Channel A Timing settings -->

This will improve stability later on

Now, lower the CPU multiplier to the next lowest setting - so if it's 10.0 change it to 8.0

Now increase the base clock until you reach that magical 4.0GHZ - or as close to it as your RAM will allow. Remember! Try not to go over your rated RAM speed. On this particular board my settings were :

Base clock : 200MHZ
CPU Multiplier : 20.0
RAM multiplier : 8.0

So the CPU is at 4000MHZ
RAM is at 1600MHZ

Save all to BIOS and restart

Now download Prime95 and to some stress testing - some recommend 8 hours - though you'll find your probably crashes a lot earlier on in the stress test.

This is because we haven't configured those voltages.

This is a bit more of a dark art rather than hard "you need these settings"

The suggested method is this :

If you're running any windows platform, not enough Vcore will result in a blue screen before boot.

So run the CPU at top Intel spec volts and then lower them until your system becomes unstable then increase so it's back stable.

The 2 main voltages we'll be changing is Vcore and VTT. Some suggest change the PLL and PCH but I personally didn't need to.

The maximum Vcore according to Intel spec is 1.5V - I REALLY recommend AGAINST starting there. Stock is 1.11250V. Many guides say no higher than 1.4V on air. You should find somewhere between 1.3V and 1.4V will be stable. Id start at 1.3875 - or as close to 1.39V as you can.

Keep the QPI or VTT voltage at 1.33 for now (maximum Intel spec)

You now want to lower the Vcore until Windows doesn't boot.

I personally did lowest voltage + highest voltage / 2 then see if Windows booted

If it does, use new voltage + lowest voltage / 2

If it doesn't use new voltage + highest voltage / 2

Highest = 1.3875V

Lowest = 1.11250V

Keep trying various voltages - eventually one setting will boot, the one below it won't.

Now run Prime95 stress test again - if it carshes - increase the Vcore slightly until it's stable.

When it's stable begin lowering the QPI or VTT until Prime95 isn't stable anymore. Then go back up 1 setting and presto - we're all done!

If it's not stable with the voltages I mentioned then you'll need to go beyond Intel spec - and you do this at your OWN risk!

My finalised settings were :

200MHZ BCLK
20.0 CPU Multiplier
8.0 RAM Multiplier
Vcore at 1.34375V
QPI or Vtt at 1.270 V
Related resources
April 19, 2010 11:02:30 AM

Ergh

"This will improve stability later on

Now, lower the CPU multiplier to the next lowest setting - so if it's 10.0 change it to 8.0 "

I obviously meant RAM multiplier
a b K Overclocking
April 19, 2010 1:43:13 PM

Very good info! I will save this for future reference
a b K Overclocking
April 19, 2010 5:41:56 PM

crazyman50000 said:
Keep the QPI or VTT voltage at 1.33 for now (maximum Intel spec)

WRONG, as per Intel's data sheet for the i5 700/i7 800 series processors the ABSOLUTE max for vtt is 1.21v

Just thought I would let you know.

April 19, 2010 5:58:36 PM

I stand corrected.

Pulled it all back to stock, 160 x 21

Just a quick question - obviously OC decreases the life of the processer but does a higher Vtt than recommended dramatically reduce the life, or would it be safe?

I was aiming for 4GHZ at maximum spec volts - windows doesnt even boot with a Vtt of 1.21V
a b K Overclocking
April 19, 2010 8:57:43 PM

Will it last for 10 years in an overclocked/overvolted state, I don't know, I've never kept a computer that long, I usually only have one for 2-3 years top. I've never had one die because of OCing in that time frame though, and I've never heard back from anyone I've sold one to stating that it died.

The reason I brought the max voltage up was because you more or less made an OCing guide and hence beginners would look at it and follow it. That is the only reason I even mentioned it. Do I think upping the vtt a little will kill your MB or CPU, no. But this is a new series and there is no track record you can fall back on to give yourself a logical reason to go one way or the other. So, it all boils down to what you are comfortable with and what risks you are willing to take with your own system. It's just not a good idea to advise beginners to exceed the specs until they are knowledgeable enough to know the risks for themselves.
April 23, 2010 8:26:06 PM

That makes sense to me. I did say Im not an expert.

I suppose time will tell...
a b K Overclocking
May 6, 2010 9:17:08 AM

DAMN all that info is almost guide worthy
June 26, 2010 3:51:02 AM

now we need a guide on overclocking on stock voltages and with power saving left on. Surely there is head room without raising voltages, if not then I am dissapointed.

On my old core2duo 6420 which had a stock speed of 2.16ghz I got it to 3ghz on stock voltage and with c1e power saving left enabled.

My thoughts are on the i5 with 1600 spec ram, would something like this work?

stock voltage for vcore
voltage for ram manually set to ram spec, imc/vtt raised if necessary to keep 0.5v gap.
BCLK set to 160
cpu multiplier left on auto (as needed for turbo mode and power saving)

so if I am not mistaken it would result in something like this.

clock speed of 160x9=1440mhz in idle mode at 0.872v
clock speed of 160x20=3200mhz in normal mode at 1.15v
more likely clock speed of 160x21=3360mhz in normal load situation as auto tends to use x21 mostly.
and in turbo mode clock speed of 160x24=3840mhz I think still uses stock voltage

so the questions are

can an i5 run at 1440mhz at 0.872v and can it also run at 3840mhz with 1 core at 1.15v and 3360mhz with all 4 cores.

I think no one has tested this in public yet. That would be a power/heat efficient overclock.

also to the OP your guide is valid enough intel revised the max vtt spec to 1.4v. although I think the 24/7 limit is less then that and 1.4v is considered the highest absolute limit.
June 26, 2010 11:39:10 AM

Electromigration is one of the reasons why an overclocked machine will have a shorter life, and why heat reduces the life of electronic components. The relevant info is on that page under "failure mechanisms", "thermal effects". This process is constant, regardless of overclock and/or voltage settings.

Of course, increasing the voltage will increase the heat AND increase the current across a (semi)conductor, exacerbating this effect. Improving cooling will in turn reduce this effect...
a b K Overclocking
June 26, 2010 3:06:05 PM

chrysalis said:
also to the OP your guide is valid enough intel revised the max vtt spec to 1.4v. although I think the 24/7 limit is less then that and 1.4v is considered the highest absolute limit.

YEAH, thanks for the update, I just looked at the June revision of the Datasheet and sure enough 1.4v Absolute max :D 

a b K Overclocking
June 26, 2010 3:40:45 PM

chrysalis said:
can an i5 run at 1440mhz at 0.872v and can it also run at 3840mhz with 1 core at 1.15v and 3360mhz with all 4 cores.

Well, I don't have a 750 but the results for an 860 are:

Stock default:
.848v Vcore @ 1199 Mhz
1.07v Vcore @ 2931 Mhz all cores 100%
1.216v Vcore @ 3330 Mhz running super Pi

@ 160 Bclk, everything else default
1.264v Vcore @ 3520 Mhz, speedstep and turbo seem to have been disabled.

I didn't try to Force it to run with turbo/speedstep, as this may be possible, but at default they didn't work with the higher Bclk. If I have time later maybe I'll play around with it a bit.

Thanks again for the voltage update. :) 
a b K Overclocking
June 28, 2010 7:13:02 AM

chrysalis said:
also to the OP your guide is valid enough intel revised the max vtt spec to 1.4v. although I think the 24/7 limit is less then that and 1.4v is considered the highest absolute limit.


Great info!

Intel is a dick! I don't think they would change it if 875K was not released.

They must did it on purpose to stop us from getting more bang for the buck through OCing the i5-750, wanting us to pay much more for the insanely
expensive X58 platform and i7.
a b K Overclocking
June 28, 2010 3:10:25 PM

andy5174 said:
They must did it on purpose to stop us from getting more bang for the buck through OCing the i5-750, wanting us to pay much more for the insanely expensive X58 platform and i7.

Maybe, but I would presume they did it because TH cooking some "budget" boards around release time. I know when I got my board (at release) the Bios said 1.33v or there abouts and then the first Bios update it went down to 1.21v.

Glad they upped it though :D 
a b K Overclocking
June 28, 2010 7:16:32 PM

I'm glad to see them 'officially' raise this as well. I've always needed , 1.31 over 3800mhz. It completely stops random reboots, which is the only symptom I have had from lowering it. Never errors in prime95 or IBT, just blip , off.
I hit 4440mhz yesterday, first time EVER, lol. Newer bios seemed to be the difference.
f10a. I was trying to get fast superpi times, my fastest was 9.37, I believe at 4350, had the memory running closer to 1600mhz. This was just a adrenaline rush/run, don't run that high for long~my disclaimer :) 
June 30, 2010 4:19:29 AM

Great OC. I wonder how well 875K will do upon the new spec considering that it's much better than 750 due to its unlocked multiplier.
a c 100 K Overclocking
July 16, 2010 2:54:10 PM

I feel like adding to this post as for the first time last night, I turned off turbo boost haha.

Ok so the absolute highest I could go with turbo on seemed to be 175 base clock. Voltages were 1.31 Vcore and 1.21 VTT. Turbo was running at 108W (in HWMonitor) and 3.68ghz up to 4.2ghz. Pretty good.

I tried and tried to get it stable at even just 177bclk and couldn't, I pumped a lot more voltage into both vcore and vtt (up to 1.36V/1.25V I think) and it wasn't stable. Wierd, considering it's such a tiny base clock increase.

I set it back to my stable settings at 175. Then disabled turbo, set the base clock to 200x19 for 3.8ghz. Kept the exact same voltages. It passed Intel Burnt Test (IBT). I upped it to 20x for an even 4ghz. This required only a slight increase of voltages, 1.325 Vcore and 1.225 VTT (iirc) and passed IBT fine. I still have to fine tune it to try and get the most efficiency, but in Vantage my CPU score went up 2k (tho GPU went down a bit :( ). Also, CPU power went down from 108W to 95W. And the temps only went up about 3C. As to efficiency, I had the highest efficiency run at 202 base clock although it had an error after a couple passes. By efficiency, I mean how close I was to the theoretical maximum computing power of the CPU (GFlops). It's calculated by doing 4 x (# of cores) x (speed in ghz). At 4ghz I was getting 11% off, at 4.05 (202bclk) I got 9.5% off. Interesting. I think I can get it more efficient tho (by adjusting voltages).

I was briefly trying to maximize my RAM speed by going to 202 or 204 base clock but couldn't get stable without a fairly big increase in voltages that I don't feel comfortable with. I'm planning to do some testing to figure out how to maximize the RAM speeds. The method is lower CPU clock, run the RAM at CL7, and see how high I can get the RAM at CL7. Once I find the max stable speed, increase to CL8 and do it again. Then the MHz difference between CL7 and CL8 is how many MHz you get per CL. Then it's easier to decide on a baseclock to match up with the highest speed you can get at any given CL, as maxing the speed of any CL should in theory be around equal performance. This then gives more options for baseclock combinations as you could have CL7, CL8, CL9 max speeds with 6, 8, and 10x RAM multipliers... anyway, I'll make a post on it when I'm done heh.
a b K Overclocking
July 16, 2010 3:44:42 PM

wolfram23 said:
the first time last night, I turned off turbo boost haha.

YEAH !!!!!! :) 
!