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How to overclock Mid 2011 iMac?

J

Jimmy Guphanti

macrumors 6502
Original poster
Mar 29, 2011
341
8
Hello,
I am wondering how to overclock the CPU of the Mid 2011 iMac. I have tried almost every overclocking tool that I could find online in Boot Camp with Windows 7, and in one way or another none of them work. All I have been able to do is overclock the GPU using the Sapphire Trixx program. I think that this stems from the 2 reasons. One of them is that the Mac does not have a legitimate BIOS, and that the hardware is so locked down that none of the software can identify the PLL of the Main board/Logic Board. I know that people have done it on other recent macs (https://forums.macrumors.com/threads/667887/) The OP of this thread does not identify the software or method used to overclock the CPU. I know that it is probably a bad idea due to the fact that the components of the 2011 iMac are so tightly and closely placed. I am using the 21.5 inch 2.7 GHz i5 Quad Core and I want to get it to 2.8 (preferably 3.0) and overclocking it by 100 MHz should not set the computer on fire or anything since I would assume that the components, especially the cooling components of the 2.7 iMac are extremely similar or congruent to those in the next model up. I know that it can be done (see above thread) I just don't know how.
Any ideas?

Thanks,
Jimmy
 
The tool used is identified later in the thread you linked to: NVIDIA System Tools. Maybe give that a try?

Intel Macs don't use BIOS; they have EFI instead. You can install rEFIt to poke around there if you want.

Also, on the Mac OS X side, check out ZDNet Clock. Chances are it won't work on your system -- it was made in 2008 for Mac Pros -- but it might be worth a look.

One more thought: Why overclock? Your iMac's CPU will Turbo Boost itself to 3.7GHz when the cores aren't all saturated. That's faster than any overclock you'll be able to achieve given the iMac's cooling capacity. The only real benefit to an OC would be for long-running, heavily multi-threaded tasks -- and then you're likely to run into heat issues.
 
I agree. what exactly are you hoping to gain from doing all this?

What are you doing all day that maxes the processor so hard that a few more MHZ would make things that much better?

If you *needed* -- as opposed to just "wanting" -- more GHZ then you should have ponied up the extra cash and got the i7 chip.
 
eggfoam said:
The tool used is identified later in the thread you linked to: NVIDIA System Tools. Maybe give that a try?

Intel Macs don't use BIOS; they have EFI instead. You can install rEFIt to poke around there if you want.

Also, on the Mac OS X side, check out ZDNet Clock. Chances are it won't work on your system -- it was made in 2008 for Mac Pros -- but it might be worth a look.

One more thought: Why overclock? Your iMac's CPU will Turbo Boost itself to 3.7GHz when the cores aren't all saturated. That's faster than any overclock you'll be able to achieve given the iMac's cooling capacity. The only real benefit to an OC would be for long-running, heavily multi-threaded tasks -- and then you're likely to run into heat issues.
Click to expand...

I want to overclock the CPU not the GPU I have tried rEFIit and unless there is really is no option to overclock or really anything related to that in the program or boot menu or what ever you want to call it. I have tried the ZD Net program and it knows that I am not on a Mac Pro and will not work. I have tried SetFSB on Windows 7 Bootcamp, which could not identify the Clock Generator. I have tried Intel Desktop Control Center, but I was unable to identify the mainboard of the computer, to be able to download the right version and no analysis software could identify it. All it would tell me is that the Mainboard vendor is Apple Computers Inc. I have tried CPU tweaker which would open and display the error "Not for your system!" and then close. I have tried ClockGen which would only show a clock for the RAM and CPU, and the overclocking options were not there, they were just missing from the program. It looked kind of like this picture that I got from Google:

clockgen.png


I have tried every program in Google, and all of them had some type of issue.

I resent paying $200 for an extra 100 MHz. PC Users can easily overclock, but Macs and PC's are different things. I resent how Apple locks down it's hardware so much in an effort to get $200 for a skimpy 100 MHz difference. For $200, I could get a 2500K and overclock to 4 GHz. But Macs do not work that way. The only reason that I did not go Hackintosh is because I have before, and it is too unstable. I have been using Mac since the days of Mac OS 8. I have such a collection of Mac Data that is not compatible with Windows.

My 2008 Mac Pro died (my basement flooded.) I needed a new computer and fast. I needed a Mac, and the iMacs had just been refreshed, and the Mac Pros are due for a new one. The iMacs are faster than the MacBook Pros and I needed thunderbolt which is also why I did not buy a Mac Pro. I turned up the fans on the mac to the point where the room is getting cold. A 100 MHz overclock in my opinion won't hurt the computer. Going from 2.7 to 2.8 (even if it is not noticeable) should not hurt at all, or cause any type of cooling problem. I bet the 2.8 GHz has the same exact cooling as the 2.7.

To conclude, 100 MHz worth of an overclock is my own personal victory over Apple. It has been done, it can be done, and I will do it.
 
Badger^2 said:
I agree. what exactly are you hoping to gain from doing all this?

What are you doing all day that maxes the processor so hard that a few more MHZ would make things that much better?

If you *needed* -- as opposed to just "wanting" -- more GHZ then you should have ponied up the extra cash and got the i7 chip.
Click to expand...

It's not the cash, it's that I do not have room for a 27" screen. I despise Apple's strategy about how if you want the higher specs, you have to buy a TV sized screen to use them with.

It's not what I am doing all day, it is how quickly it is being done.
 
Jimmy Guphanti said:
It's not the cash, it's that I do not have room for a 27" screen. I despise Apple's strategy about how if you want the higher specs, you have to buy a TV sized screen to use them with.

It's not what I am doing all day, it is how quickly it is being done.
Click to expand...

If you overclock it to any extent you'll soon see why they put the higher TDP chips in the 27". BZZZZZZZTTTT.
 
NutsNGum said:
Isn't the 2.8 an i7? It's not the same as an i5 for a variety of reasons.
Click to expand...

I think the OP may have missed the point that the $200 upgrade was for a different cpu (i5 to an i7). I had to double check the apple store to make sure that it really wasn't that ridiculously priced to upgrade from a 2.7 to a 2.8 for just a small speed bump.
 
It doesn't seem like you have much of a reason for overclocking other than frustration toward Apple, but for what it's worth, OP: as I said in my earlier post and you dismissed, the thread you already found discussed using NVIDIA System Tools to overclock an iMac's CPU. I completely understand that you want to overclock the CPU and not the GPU. The thread you found BEFORE you started this thread, and which you linked to in your initial post, claims that this tool will do what you want. Why not try it? Maybe it works.

Otherwise, I'd say just forget about it. Hackintoshes can be quite fast and stable if you're willing to invest the time to set them up right and be cautious about software updates. It depends on what your time is worth to you.
 
Hi, coming from building liquid cooled PC before switching to imac as main computer, I would suggest you abandon the idea.

There are simply too many adjustments need to be done even for the moderate overclocking you try to achieve.

For example to maintain a stable OC in general, you need to disable those in BIOS:

Limit CPUID Maximum
Power Technology
C1E Support
OverSpeed Protection
Spread Spectrum

And enable:

Internal PLL Overvoltage
Execute Disable Bit
Intel Virtualization Tech


It's more than just change the Computer Base Frequency (FSB) setting available in most overclocking software.


Also those software may automatically increase any of the following settings:

VCore
VCCSA (System Agent)
VDDQ (RAM VOLTS)
VCCPLL (Phased-Locked Loop)
VCCIO (I/O Supplied voltage)

Which can fry CPU and motherboard and void your warranty due to the higher voltages.

The ONLY way to achieve a safe and stable OC is to do the dirty work manually in BISO and don't trust overclocking software.
Since there is no way for us to edit those settings and limited air flow in the imac. There is little point OC the imac, beside there will be very limited increase for 100 to 300 MHz OC.
 
eggfoam said:
It doesn't seem like you have much of a reason for overclocking other than frustration toward Apple, but for what it's worth, OP: as I said in my earlier post and you dismissed, the thread you already found discussed using NVIDIA System Tools to overclock an iMac's CPU. I completely understand that you want to overclock the CPU and not the GPU. The thread you found BEFORE you started this thread, and which you linked to in your initial post, claims that this tool will do what you want. Why not try it? Maybe it works.

Otherwise, I'd say just forget about it. Hackintoshes can be quite fast and stable if you're willing to invest the time to set them up right and be cautious about software updates. It depends on what your time is worth to you.
Click to expand...

When I heard NVIDIA system tools I imagined that they were talking about overclocking the GPU just because I heard the word NVIDIA. I apologize that I dismissed that. I am going to look into the program when I get home from work.
 
Jimmy Guphanti said:
When I heard NVIDIA system tools I imagined that they were talking about overclocking the GPU just because I heard the word NVIDIA. I apologize that I dismissed that. I am going to look into the program when I get home from work.
Click to expand...

I understand, no worries. I was just a little frustrated that you already had the link to the thread and hadn't read it even as much as I had. :) Good luck!
 
eggfoam said:
I understand, no worries. I was just a little frustrated that you already had the link to the thread and hadn't read it even as much as I had. :) Good luck!
Click to expand...

I just tried to install NVIDIA system tools, and I should have known that since I have an AMD 6770, the NVIDIA tools would not work, which they did not, flaunting a large non compatibility error. The person in the thread was using a MacBook Pro which Pre-2011 refresh had NVIDIA GPUs, which is probably why it worked. I am thinking that since overclocking software is mainly designed for Windows based rigs, I am out of luck. The only way to overclock now is at either an EFI or Hardware level. For me, Hardware tampering is something I am not willing to risk. Apple probably has it so there is no way to do so. The last time I did that was on a Bondi Blue G3. I'll revisit rEFIit to see what I can see.
 
I just tried rEFIt and through my testing, it appears that rEFIt or shell commands do not allow access to the level that would be required to overclock the CPU. I am beginning to think that this is not possible. I have one last idea though. I just remembered that about 10 years ago, a friend of mine told me that he had overclocked an iBook with a program that came with the CHUD tools, but I can't remember the name and neither could he. I remember that it had initials or something in it. I googled it and I could not find anything. I do remember that it had access to CPU information. Any ideas?
 
I'm amazed nobody has told you this yet...

You can't overclock the iMacs. Point blank. Intel sell two CPU types for the Sandy Bridge line, K and non-K (ie: i5 2500K and i5 2500). The chips are identical apart from the fact that a K CPU has an unlocked multiplier that allows overclocking, and the non-K chips have a locked one.

Apple, of course, use non-K chips (they are a little cheaper), so they don't have an unlocked multiplier, which in turn means they are impossible to overclock.


http://www.anandtech.com/show/4083/...-core-i7-2600k-i5-2500k-core-i3-2100-tested/3
 
You really think an all in one can cope with overclocking temps? It feels like its about melt even running The Sims 3 for 30 mins.
 
This is odd, from the OPs posts, he seems intelligent enough, although he can't seem to tell the difference between two different types of CPUs. Trolling?
 
You can't overclock an Imac CPU! You just don't have acces to the FSB generator. plus there's heaps of other stuff as 88 king discribes in his post.

But saying that an all in one can't handle overclocking or overclock non k intel CPU's is nonsense because you can even overclock laptops where heat is even a bigger issue and you can overclock standard non k cpu's over the FSB but only by a small margin of around 5%.
 
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