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mid 2011 27" iMac CPU upgrade - XEON E3-1275

stevescivic

macrumors member
Original poster
Sep 28, 2006
33
3
So I picked up a used Mid 2011 iMac to tinker with and I wanted to put some upgrades to the test.

I was thinking of:
1. Doing an SSD upgrade - this is super easy with the OWC thermal sensor SATA cable.
2. CPU upgrade - was thinking of going with the XEON E3-1275 with integrated graphics to avoid the sleep/kernel panic issue.
3. K2100M graphics card upgrade.

Can the folks here chime in on the XEON processor upgrade? It seems like its plug and play with some noticeable improvements but the caveat is that it isn't officially supported and for processors that don't have integrated graphics that when the computer wakes from sleep that a kernel panic occurs. XEON processors seem to be cheaper than the i7-2600 equivalents. Is there a clear way to identify the proper E3-1275 chip to buy? Looking at images on ebay it would appear that the proper one to buy is the e3-1275v1 or simply e3-1275. Other versions seems to be clearly marked on the cpu as 1275v2, 1275v3, etc.

Also, is there a clear definitive write up on how to get that K2100M bios and open core installed properly? I see snippets here and there but not a true write up that covers a complete end to end install and config using the latest patches/fixes/etc. I'm VERY competent at taking apart the 2010/2011 iMacs so that isn't the problem FYI the K2100M I bought came out of a Dell laptop which I believe is the ideal card to get. From all the info I've read, I believe I need to:
1. Make sure I'm running at least high sierra and have applied all patches to system before proceeding.
2. Create a boot loader USB drive
3. Swap card out to the K2100M and leave the internal drives disconnected so it boots from the USB boot loader.
4. Plug in an ethernet cable, boot computer and wait for at least 1 minute.
5. Acquire "Mac under mod" IP
6. SSH into the "mac under mod" and then...????

Your input would be immensely appreciated. I'm receiving my GPU this Friday and hoping to buy the CPU and have it ready for install by next weekend.

Thanks!
 

cheaptech

macrumors newbie
Aug 10, 2020
23
7
I wouldn't buy the OWC sensor cable, way overpriced for its function. Use software instead. Or modify the SATA cable yourself. It involves cutting and then joining two wires. An SSD will never get hot enough to worry about. Also I just tape the SSD into place.

Curtis Grossman covers the Xeon in his youtube videos. he also covers the Xanderson method of flashing the gpu.

You haven't seen the dedicated thread for 2011 GPU ugrades? It is the authority read it then reread again and again.
 
Last edited:

Nguyen Duc Hieu

macrumors 6502
Jul 5, 2020
472
111
Ho Chi Minh City, Vietnam
1. CPU

2. GPU

3. Thermal sensor:
It will be cheaper if you buy another ODD sensor and put it to the place of HDD sensor. They have the same size.
There is no HDD sensor. It's only a cable. The sensor is on the HDD board. If it's not certified by Apple (adding some code to the HDD firmware for external thermal read-out), you won't get the thermal data out.
The cheapest solution is shorting the two wire of the cable and use Mac Fan Control.

4. SSD
If you can get a 2x2.5in to 3.5in adapter, you can install upto 3 2.5in SSD/HDD into the iMac. Just leave the ODD there as airpressure wall.
 

stevescivic

macrumors member
Original poster
Sep 28, 2006
33
3
I wouldn't buy the OWC sensor cable, way overpriced for its function. Use software instead. Or modify the SATA cable yourself. It involves cutting and then joining two wires. An SSD will never get hot enough to worry about. Also I just tape the SSD into place.

Curtis Grossman covers the Xeon in his youtube videos. he also covers the Xanderson method of flashing the gpu.

You haven't seen the dedicated thread for 2011 GPU ugrades? It is the authority read it then reread again and again.


Thanks for sharing that. What Curtis did to his iMac is precisely what I want to put into my new acquired 2011
iMac. Its been many years since I've done modding on any of these older machines and reading the GPU upgrade thread can be quite daunting for me. Looking back at some of my work I did modding my own 2010 iMac back in the day that I'm probably overthinking how to do the upgrade.

I just purchased a K2100M and Xeon e3-1275 :). Next is to find a decently priced SSD and then replace the spinny drive in the computer to get the most speed out of my new toy.

What was funny about how this entire project started was my itch to buy a new iMac but under the recommendations of others on this forum and my lack of a "real" need for a new Mac that I was still wanting to satisfy this itch I have for a faster and newer machine. I first bought the K2100M card for my older 2010 iMac i7 but was afraid of ruining my primary computer and so just when I posted the question about the GPU and CPU upgrade was actually the day I snagged myself a 2011 iMac to use as my "tester" machine.

Long story short, if I get the 2011 iMac up and running I will likely transplant the K2100m into my 2010 iMac and the put something beefier like a K5100 into the 2011 iMac since it has the 3 pipe heatsink in it.

WRT the SSD install.... if I use the larger B sized MXM cards where it extends into the hard drive bay will it get in the way of the 3.5" to 2.5" drive bay mounting tracking I intend to install? I know you said to just use double sided tape to mount the SSD but I would prefer to bolt things into place if I can.

Great tip about the OWC cable. I had no idea! My 2010 thankfully didn't need it and I was able to just use an optical drive temperature sensing cable to make it work just fine (thank goodness I put it in, the WD black drive I put in my 2010 does run super hot).

Thanks!
 

cheaptech

macrumors newbie
Aug 10, 2020
23
7
Thanks for sharing that. What Curtis did to his iMac is precisely what I want to put into my new acquired 2011
iMac. Its been many years since I've done modding on any of these older machines and reading the GPU upgrade thread can be quite daunting for me. Looking back at some of my work I did modding my own 2010 iMac back in the day that I'm probably overthinking how to do the upgrade.

I just purchased a K2100M and Xeon e3-1275 :). Next is to find a decently priced SSD and then replace the spinny drive in the computer to get the most speed out of my new toy.

What was funny about how this entire project started was my itch to buy a new iMac but under the recommendations of others on this forum and my lack of a "real" need for a new Mac that I was still wanting to satisfy this itch I have for a faster and newer machine. I first bought the K2100M card for my older 2010 iMac i7 but was afraid of ruining my primary computer and so just when I posted the question about the GPU and CPU upgrade was actually the day I snagged myself a 2011 iMac to use as my "tester" machine.

Long story short, if I get the 2011 iMac up and running I will likely transplant the K2100m into my 2010 iMac and the put something beefier like a K5100 into the 2011 iMac since it has the 3 pipe heatsink in it.

WRT the SSD install.... if I use the larger B sized MXM cards where it extends into the hard drive bay will it get in the way of the 3.5" to 2.5" drive bay mounting tracking I intend to install? I know you said to just use double sided tape to mount the SSD but I would prefer to bolt things into place if I can.

Great tip about the OWC cable. I had no idea! My 2010 thankfully didn't need it and I was able to just use an optical drive temperature sensing cable to make it work just fine (thank goodness I put it in, the WD black drive I put in my 2010 does run super hot).

Thanks!

Buy a cheap SSD since performance is bottled necked by the SATA on the 2011. I use 256gb PNY for $26. Or try to buy used dirt cheap.
 

BeatCrazy

macrumors 68030
Jul 20, 2011
2,506
1,197

daniq

macrumors newbie
Oct 10, 2020
7
3
So I picked up a used Mid 2011 iMac to tinker with and I wanted to put some upgrades to the test.

I was thinking of:
1. Doing an SSD upgrade - this is super easy with the OWC thermal sensor SATA cable.
2. CPU upgrade - was thinking of going with the XEON E3-1275 with integrated graphics to avoid the sleep/kernel panic issue.
3. K2100M graphics card upgrade.

Can the folks here chime in on the XEON processor upgrade? It seems like its plug and play with some noticeable improvements but the caveat is that it isn't officially supported and for processors that don't have integrated graphics that when the computer wakes from sleep that a kernel panic occurs. XEON processors seem to be cheaper than the i7-2600 equivalents. Is there a clear way to identify the proper E3-1275 chip to buy? Looking at images on ebay it would appear that the proper one to buy is the e3-1275v1 or simply e3-1275. Other versions seems to be clearly marked on the cpu as 1275v2, 1275v3, etc.

Also, is there a clear definitive write up on how to get that K2100M bios and open core installed properly? I see snippets here and there but not a true write up that covers a complete end to end install and config using the latest patches/fixes/etc. I'm VERY competent at taking apart the 2010/2011 iMacs so that isn't the problem FYI the K2100M I bought came out of a Dell laptop which I believe is the ideal card to get. From all the info I've read, I believe I need to:
1. Make sure I'm running at least high sierra and have applied all patches to system before proceeding.
2. Create a boot loader USB drive
3. Swap card out to the K2100M and leave the internal drives disconnected so it boots from the USB boot loader.
4. Plug in an ethernet cable, boot computer and wait for at least 1 minute.
5. Acquire "Mac under mod" IP
6. SSH into the "mac under mod" and then...????

Your input would be immensely appreciated. I'm receiving my GPU this Friday and hoping to buy the CPU and have it ready for install by next weekend.

Thanks!
Hi

I'm finally upgraded my iMac 2011 27" to CPU Xeon E3-1275 and GPU K2100M but have next issues on the latest Catalina 10.15.7 (I used this tutorial https://helloworldcodes.com/index.p...100m-graphics-card-swap-and-install-catalina/ but it's not help)

1. Black screen load and nothing happened if you don't press to "option". When I add kexts I see this error
Invalid signature -67030 for kext <OSKext 0x7fd19e5070b0 [0x7fff8d0dfcc0]> { URL = "file:///Library/Extensions/LegacyUSBVideoSupport.kext/", ID = "com.parrotgeek.LegacyUSBVideoSupport" }

(at this moment it's primary issue)
2. Quick Sync not working (SIP disabled and AppleGraphicsControl.kext added but QS don't work)
3. Brightness control through opencore (open core can't load Catalina Error "Error: Already started returned from Opencore.efi")
4. "About iMac" see my CPU like Intel Core i5, but app MacX Video Converter see my CPU like Xeon

I hope anyone can help me;)
 

Nguyen Duc Hieu

macrumors 6502
Jul 5, 2020
472
111
Ho Chi Minh City, Vietnam
WRT the SSD install.... if I use the larger B sized MXM cards where it extends into the hard drive bay will it get in the way of the 3.5" to 2.5" drive bay mounting tracking I intend to install? I know you said to just use double sided tape to mount the SSD but I would prefer to bolt things into place if I can.

It depends what kind of 3.5" to 2.5" drive bay you will use.
A small and cheaper one will not.
A driver bay that is the same bulky size as a 3.5" HDD will definitely get in the way of the MXM-B card.
 

daniq

macrumors newbie
Oct 10, 2020
7
3
Hi

I'm finally upgraded my iMac 2011 27" to CPU Xeon E3-1275 and GPU K2100M but have next issues on the latest Catalina 10.15.7 (I used this tutorial https://helloworldcodes.com/index.p...100m-graphics-card-swap-and-install-catalina/ but it's not help)

1. Black screen load and nothing happened if you don't press to "option". When I add kexts I see this error
Invalid signature -67030 for kext <OSKext 0x7fd19e5070b0 [0x7fff8d0dfcc0]> { URL = "file:///Library/Extensions/LegacyUSBVideoSupport.kext/", ID = "com.parrotgeek.LegacyUSBVideoSupport" }

(at this moment it's primary issue)
2. Quick Sync not working (SIP disabled and AppleGraphicsControl.kext added but QS don't work)
3. Brightness control through opencore (open core can't load Catalina Error "Error: Already started returned from Opencore.efi")
4. "About iMac" see my CPU like Intel Core i5, but app MacX Video Converter see my CPU like Xeon

I hope anyone can help me;)
Solved 1 and 3 issue by video tutorials from Curtis youtube channel. Still looking 2 and 4 issue)
 
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