iM 4,1-14,4 iMac 2010 (11,x) Successful overclocking achieved!

[Maggehagge]

Holy ....!

I Successfully overclocked iMac 2010 with a i7-875k

I have the unlocked i7-875k so that could make sense. But right now i can configure the turbo ratios to anything i want and the power limit to anything i want which means i can get have all cores on turbo or higher. CPU power delivery and stability is the limit here.

Will post pictures when i log from the imac. I verified with cinebench R15 scores going from 450 points stock to 527 points with all cores boosting to x28=3733Mhz

i only got it stable to x28 for now but as you can see my current power draw is about 125 W and default max is 95 W.

im off to bed now but will post how to do it later.

EDIT:
This is not completly finished yet. Power limit and turbo ratios still need to be applied after boot but it still works. Give me a few days and i might have a full patch that sets everything at POST and regardless of operating system you use.

Okay here is how i did it. In Windows, changing the multiplier was done in Intel XTU v4.something. It has to be an older version otherwise it probably will not work with these CPUs.

Multiplier control seems to be unlocked by default actually but power control is not so we dont get much from just increasing turbo frequency becasue as soon as enough load is put on the cpu it clocks down to stock turbo ratios.

NOTE: I have also removed write protection so i can flash the EFI ROM from windows using intel FPT.(flash programming tools. I think you need to have the correct version. Every platform uses a different version. I used Flash Programming Tool(Windows): 6.0.40.1214.)

I dont know if this write protect removal is actually required for these values to be changes from OS.

So for unlocking MSR writes to register 0x1A MSR_TURBO_POWER_CURRENT_LIMIT:

F7731B4C-58A2-4DF4-8980-5645D39ECE58 10 P:488BD82500000020:488BD8B800000030
Use UEFIPatch to apply

This changes Bit 29 of 0xCE MSR_PLATFORM_INFO to 1.

change the last section from 20 -> 30. Now you can change power and current limit in RW everything for windows and msr-tools in linux and probably MacOS aswell? Multiplier should be changeable through RW everything or msr-tools aswell. I used ChatGPT 😆 to convert the MSR values of the power limit in to the hex values needed. Worked perfectly and saves the hassle.

Bit 29:
Programmable TDC-TDP Limit for Turbo Mode (R/O)
When set to 1, indicates that TDC and TDP Limits for Turbo mode are
programmable. When set to 0, indicates TDC and TDP Limits for Turbo
mode are not programmable.

Full patch for boot time power and turbo limits will come. I think i already know how to do it but this is safer for now.

Here is how to use RW everything. Open CPU MSR in the access menu. Click the user tab and then the user button(or F5). Then type 0x1AC, press add and then done. double-click the 0x1AC row that hopefully appeared and then this window will show:

You will change the lower row that currently for me say 02 C8 02 F8 which is stock. It looks greyed out but just click it and enter numbers and press done. Use chatgpt to calculate new limits but i can give some examples or if you request i can do it for you.

EDIT:
For 130 W and 120 A limit:
0x83C08410

83 C0 84 10

Stock is 95 W and 89 A

Enjoy!

 

[iPhone_se]

Great work! I would like to apply your Turbo Power Limit disable firmware mod above to my 2011 12,2 iMac to see if I can get closer to the max CPU power draw of 95W out of it under Cinebench and Prime95 after applying m0bil’s excellent Turbo OC patch in the other thread. Do you think that your Bit 29 TDC-TDP Limit for Turbo mod would work on the 2011 firmware also?

 

[Maggehagge]

Great question. I can look into it but it might be very possible. I'm also trying find if I can overvolt a bit. 4ghz would be sweet.

Edit: @iPhone_se I didnt know that power was a limiter holding iMac 2011 users back. Are you telling me that full boost on all cores is not possible right now during heavy load at 4-4.4Ghz?

 

[Maggehagge]

Btw, I can confirm that the patch that @m0bil made for removing EFI ROM write protection for 2011 imac is exactly the same, verified in the code and results and working on 2010 imac 11,3(27 inch model). I can not for certain say now that its the same on all 2010 imac's but i think so.

Check his thread/repository for the patch. We should maybe think of merging 2010 and 2011 github repository for easier access.

 

[iPhone_se]

Edit: @iPhone_se I didnt know that power was a limiter holding iMac 2011 users back. Are you telling me that full boost on all cores is not possible right now during heavy load at 4-4.4Ghz?

On my i7-2600 with m0bil’s Turbo OC patch set to X44 I can get constant 3.9 GHz on all 4 cores running the CPU test in Intel Power Gadget with 62W to 65W showing in the gadget power graph. But when I switch the CPU test to either Cinebench or Prime95 in Windows bootcamp, the CPU speed throttles down to only 3.6 GHz on all 4 cores to keep the power in the same 65W range due to the firmware power limiting that you have discovered. I would like to keep the same 3.9 GHz speed constant in Cinebench and Prime95 to get the maximum 95W out of the i7-2600. See my last post in the other thread about a week ago.

 

[iPhone_se]

View attachment 2509108


Here is how to use RW everything. Open CPU MSR in the access menu. Click the user tab and then the user button(or F5). Then type 0x1AC, press add and then done. double-click the 0x1AC row that hopefully appeared and then this window will show:

View attachment 2509109
You will change the lower row that currently for me say 02 C8 02 F8 which is stock. It looks greyed out but just click it and enter numbers and press done. Use chatgpt to calculate new limits but i can give some examples or if you request i can do it for you.

EDIT:
For 130 W and 120 A limit:
0x83C08410

83 C0 84 10

Stock is 95 W and 89 A

Enjoy!

Thanks for adding the additional details to changing the firmware power and current limits! Awesome hacking skills!

So CPU register 0x1AC sets the values for the allowed CPU power and current limits (after setting Bit 29 to allow R/W)? Can you please decode for me how hex values 83 C0 84 10 set the power to 130W and 120A?

I might try this on my 2011 iMac but before I do I must understand completely the code changes being made to the firmware. Any chance that you could make this into a text patch like m0bil’s patches so that it could be applied with UEFIPatcher? Thanks for all of the great work so far!

 

[Maggehagge]

I looked into doing this on the 2011 imac but the code was not identical and i have not even made a UEFIpatch version for 2010 yet. Just for unlocking the R/W which means we can control it from OS.

Maybe you can hardpatch the limits directly and ignore unlocking the R/W on the 2011? I havent looked for that.

I tried a Vcore mod yesterday on the 2010 model but im not sure if it gave any results or if i just accidently set the vcore the same as it was already and therefore saw no change.

I can not help you decode why 83 C0 84 10 is 130W and 120A(120A is not needed i have noticed, i berly reach stock 89A but 130W is almost too low at 3733Mhz). Its in the intel datasheets and the math is too much for me 😆

from the datasheet:

If you copy the 1ACH(which is same as 0x1AC) section and ask chatgpt about it, it can show you how it works. Try using the o4-mini GPT-model, also called "Reason" for better results.

 

[Maggehagge]

On my i7-2600 with m0bil’s Turbo OC patch set to X44 I can get constant 3.9 GHz on all 4 cores running the CPU test in Intel Power Gadget with 62W to 65W showing in the gadget power graph. But when I switch the CPU test to either Cinebench or Prime95 in Windows bootcamp, the CPU speed throttles down to only 3.6 GHz on all 4 cores to keep the power in the same 65W range due to the firmware power limiting that you have discovered. I would like to keep the same 3.9 GHz speed constant in Cinebench and Prime95 to get the maximum 95W out of the i7-2600. See my last post in the other thread about a week ago.

I see what you are trying to do but i promise you that getting a K model cpu like 2600K is so worth it. it might be like 30-40 euro and the swap is tedious but not too hard even for inexperienced if you are carfeul.

That maybe isnt solving the problem tho. Just helping you get even more performance.