iM 4,1-14,4 2011 iMac Graphics Card Upgrade

[limmers2015]

Hello everyone:

After reading all of the posts in this thread about GPU upgrades for a mid-2011 iMac 21.5" (iMac 12,1), I decided (nearly 9 months ago now) to upgrade from my 6750M to a GTX 765M. It worked well (no native brightness control, boot screen, or non-standard boot modes, eg recovery mode, single-user mode,...), but I'm still running into performance issues. I originally upgraded to get up to 2GB VRAM and Metal support under High Sierra to be able to play the game "Farming Simulator 19". I am now able to do that, but even with the in-game graphics settings turned way down, I'm still getting an average of 10-15 FPS.

Here's my question: Is it worthwhile to try and go further with my GPU?

If so, what should I get? I was thinking of either a 780M or an 880M.

If not, is there any way to get better performance out of my 765M?

I did see someone way back in the thread talk about needing an Apple-compatible VBIOS to get the best performance out of the card. Also, it'd be great to get back native brightness control, the boot screen, and access to the other boot modes. Would a VBIOS update help with those?

Just in case it matters, I do not have any non-Apple computer to put the GPU in for reflashing the VBIOS, nor do I have Windows to bootcamp to. I could do a Linux install though. I also have an external monitor hooked up, if I end up needing it.

Here's my machine's current specs/hardware info:



My sincere thanks and gratitude to everyone involved in this process! Without you all, I would've been dead in the water a long time ago.

Edit: While I'm at it, is it worth replacing the CPU and/or PSU as well? I would only do the PSU if I had to for wattage reasons, but I would love more CPU power. The CPU in the machine currently is an i5-2400S. I was thinking of an i7-3770. Does anyone have thoughts/suggestions on that front?

I also forgot to mention it, but I've got a 500GB SSD boot drive, with an additional 500GB of HDD storage from the original drive. 12GB of RAM, in a 2 x 4GB, 2 x 2GB configuration.

Edit 2: I really want to stick with hardware that will be able to go to Mojave, Catalina, and then possibly further. This, unfortunately, means no Maxwell, Pascal, Volta, or Turing-based cards. I think this rules out the 9** series completely, but I may be wrong. Basically, I just want the most GPU horsepower I can get out of this machine while still being able to go further with my OS.

 

[1991Nick]

I'm in the same situation here. Here are my specs

I also want to put the BEST possible card that I can in this iMac so I can couninue doing graphics intensive work as well as use Catalina patcher to run Catailna or at least Mojave. I also don't trust this card very much. It already broke and I had to Bake it in my oven....
[automerge]1588858993[/automerge]
Also note that everything in this iMac is Factory except the hard drive which is now an ssd

 

[João Campos Ribeiro]

If you use Open Core and Fake "PWM-Info" like I talked about so many times now, you can enable Target Display Mode over thunderbolt. It's not specific to the card, it's enabled if the display is set to "internal".

Thanks! My question was specific about the Nvidia GTX 675MX cards that Nick [D]vB is selling there as a direct replacement.

 

[limmers2015]

I'm in the same situation here. Here are my specsView attachment 912932
I also want to put the BEST possible card that I can in this iMac so I can couninue doing graphics intensive work as well as use Catalina patcher to run Catailna or at least Mojave. I also don't trust this card very much. It already broke and I had to Bake it in my oven....
[automerge]1588858993[/automerge]
Also note that everything in this iMac is Factory except the hard drive which is now an ssd

Well, I at least know and can confirm that a 765M will work, even without any special VBIOS reflashing or other wizardry. I got one off of eBay for only about $100. It's served me well so far. Installing it was a pain, mostly because I had never been that far inside my computer before. It went from completely stock to the 765M and SSD all in one shot.
One note: Make sure you have some good, new thermal compound (and probably some little heatsinks/thermally conductive pads). I have a sinking suspicion that some of the components around the main GPU die on my card are not being cooled properly. I'm also seeing a temperature differential between the die and the heatsink of up to 10F at idle (PECI reading 122 right now, Heatsink reading 115), 40F under heavy load (PECI up at around 170F, Heatsink gets up to 130F). I just reused the thermal compound that was on my old 6750 GPU. I had forgotten to get some new thermal compound for the mod. That's probably hurting my performance slightly from thermal throttling. I wonder how hot it would get with good thermal compound, maybe even liquid metal. I've got the 2-pipe heatsink, not the 3 pipe one.

 

[highvoltage12v]

Thanks! My question was specific about the Nvidia GTX 675MX cards that Nick [D]vB is selling there as a direct replacement.

It probably will in High Sierra, The newer Mac OS' they can enter TDM but when leaving they go to a black screen/eventually a Kernel Panic. It is most likely a Kext/framework problem. I looked into it a bit by swapping things with high Sierra but never came to a perfect solution.
[automerge]1588860722[/automerge]

Hello everyone:

After reading all of the posts in this thread about GPU upgrades for a mid-2011 iMac 21.5" (iMac 12,1), I decided (nearly 9 months ago now) to upgrade from my 6750M to a GTX 765M. It worked well (no native brightness control, boot screen, or non-standard boot modes, eg recovery mode, single-user mode,...), but I'm still running into performance issues. I originally upgraded to get up to 2GB VRAM and Metal support under High Sierra to be able to play the game "Farming Simulator 19". I am now able to do that, but even with the in-game graphics settings turned way down, I'm still getting an average of 10-15 FPS.

Here's my question: Is it worthwhile to try and go further with my GPU?

If so, what should I get? I was thinking of either a 780M or an 880M.

If not, is there any way to get better performance out of my 765M?

I did see someone way back in the thread talk about needing an Apple-compatible VBIOS to get the best performance out of the card. Also, it'd be great to get back native brightness control, the boot screen, and access to the other boot modes. Would a VBIOS update help with those?

Just in case it matters, I do not have any non-Apple computer to put the GPU in for reflashing the VBIOS, nor do I have Windows to bootcamp to. I could do a Linux install though. I also have an external monitor hooked up, if I end up needing it.

Here's my machine's current specs/hardware info:
View attachment 912926
View attachment 912927

My sincere thanks and gratitude to everyone involved in this process! Without you all, I would've been dead in the water a long time ago.

Edit: While I'm at it, is it worth replacing the CPU and/or PSU as well? I would only do the PSU if I had to for wattage reasons, but I would love more CPU power. The CPU in the machine currently is an i5-2400S. I was thinking of an i7-3770. Does anyone have thoughts/suggestions on that front?

I also forgot to mention it, but I've got a 500GB SSD boot drive, with an additional 500GB of HDD storage from the original drive. 12GB of RAM, in a 2 x 4GB, 2 x 2GB configuration.

Edit 2: I really want to stick with hardware that will be able to go to Mojave, Catalina, and then possibly further. This, unfortunately, means no Maxwell, Pascal, Volta, or Turing-based cards. I think this rules out the 9** series completely, but I may be wrong. Basically, I just want the most GPU horsepower I can get out of this machine while still being able to go further with my OS.

Your problem is the 21.5" iMac, it can only sustain boost with an MXM-B card for a few seconds before dropping back down.

Before Proceeding make sure you don't have a traditional HDD in your iMac using the +12V line:
You can improve things slightly by using Open Core with the Config I have that makes your iMac 12,1 is an iMac Pro so it loads different Power Management kexts, seeing that you are still booted with High Sierra its still loading the profile for a 6770M/6750M which also hurts performance.

You never flashed your card for Boot-screens... so using Opencore is not possible until you flash your card...

 

[limmers2015]

It probably will in High Sierra, The newer Mac OS' they can enter TDM but when leaving they go to a black screen/eventually a Kernel Panic. It is most likely a Kext/framework problem. I looked into it a bit by swapping things with high Sierra but never came to a perfect solution.
[automerge]1588860722[/automerge]

Your problem is the 21.5" iMac, it can only sustain boost with an MXM-B card for a few seconds before dropping back down.

Before Proceeding make sure you don't have a traditional HDD in your iMac using the +12V line:
You can improve things slightly by using Open Core with the Config I have that makes your iMac 12,1 is an iMac Pro so it loads different Power Management kexts, seeing that you are still booted with High Sierra its still loading the profile for a 6770M/6750M which also hurts performance.

You never flashed your card for Boot-screens... so using Opencore is not possible until you flash your card...

Is it even worth trying to flash the card if I will end up replacing it shortly? If and when we decide to upgrade my Dad's 27" mid-2011 imac (operating under the assumption that I do end up replacing my 765M with something like an 880M, and that we use my "castoff" card in his machine), would we have to change the VBIOS to specifically work with that? Or would the same one work for both?

 

[highvoltage12v]

Is it even worth trying to flash the card if I will end up replacing it shortly? If and when we decide to upgrade my Dad's 27" mid-2011 imac (operating under the assumption that I do end up replacing my 765M with something like an 880M, and that we use my "castoff" card in his machine), would we have to change the VBIOS to specifically work with that? Or would the same one work for both?

Honestly, you should flash the 765M and install it in the 27" iMac, there you will see how the card truly performs. As for future MXM cards to consider buying, due to our current situation of only certain WX7100 cards working, I'd go for a GTX 780M; the future is bright (actually dimmable lol) for this card and is a decent performer.

You really shouldn't be putting MXM-B cards in a 21.5" iMac, mine randomly reboots when not booted with OpenCore in Newer OS', you're using High Sierra, which masks the problem.... but also makes the card under perform.

 

[limmers2015]

Honestly, you should flash the 765M and install it in the 27" iMac, there you will see how the card truly performs. As for future MXM cards to consider buying, due to our current situation of only certain WX7100 cards working, I'd go for a GTX 780M; the future is bright (actually dimmable lol) for this card and is a decent performer.

You really shouldn't be putting MXM-B cards in a 21.5" iMac, mine randomly reboots when not booted with OpenCore in Newer OS', you're using High Sierra, which masks the problem.... but also makes the card under perform.

Do you think that an 880M would actually work? Supposedly it is Kepler-based (The 8** series is a weird mixed-architecture bunch). I would kinda like the increased VRAM from the 880M, as the 2GB on the 765M is the bare minimum for FS19.

Also, just so I know, what are the specific issues with MXM-B cards in the 21.5"? I understand that they are longer, and interfere somewhat with the HDD mount, but what other issues are there?

I am aware that I went from a 35W TDP AMD 6750M to a 75W TDP Nvidia 765M, and that the computer definitely would run hotter if I didn't have my fans set really aggressively, but I haven't had any other issues.

Maybe I'm just ignorant of the issues with MXM-B cards in an MXM-A location, but there's always room for learning...

Edit: I’ve found a good deal on an 880M, so that’s what has me really looking to see if it will work the way I want. Only $200 for the thing. 8GB VRAM. Seems like a steal, but I don’t want to sink $200 into the card if it won’t do what I want it to do.

 

[highvoltage12v]

Do you think that an 880M would actually work? Supposedly it is Kepler-based (The 8** series is a weird mixed-architecture bunch). I would kinda like the increased VRAM from the 880M, as the 2GB on the 765M is the bare minimum for FS19.

Also, just so I know, what are the specific issues with MXM-B cards in the 21.5"? I understand that they are longer, and interfere somewhat with the HDD mount, but what other issues are there?

I am aware that I went from a 35W TDP AMD 6750M to a 75W TDP Nvidia 765M, and that the computer definitely would run hotter if I didn't have my fans set really aggressively, but I haven't had any other issues.

Maybe I'm just ignorant of the issues with MXM-B cards in an MXM-A location, but there's always room for learning...

We currently have no Modified for bootscreen for the 880M, but if we did i'd say go for one. I know the 780m has only a 4GB VRAM.

The 21.5" was designed for MXM-A cards so maximum wattage output was 55W. When I had GTX 770M in my iMac it would constantly reboot just doing simple but Airport/Sata intensive tasks. Basically the card was drawing too much from the PSU so when other devices inside needed the resources the iMac would just reboot. Now because I accidently own a 765M i'd figure i'd try it again and see what happens. In Mojave/Catalina I will still have random reboots just not as often because the iMac can just barely handle the 50-75w spikes from the card, but still can randomly reboot when downloading something large like downloading an ISO file, and then minimizing the Safari window. I have only 2 SSD's in my system plus the original Optical drive, so no HDD's on the 12V rail for me. Also you're only on a core i5 I have an i7 2600s which could make the situation worse. The TLDR is the PSU in the 21.5" iMac can't handle the larger MXM-B card. This should be linked on page 1. Tell you what. I'll go post some heaven/valley benchmarks and we can compare them together. I think your i5 could actually be the bottleneck.

 

[limmers2015]

We currently have no Modified for bootscreen for the 880M, but if we did i'd say go for one. I know the 780m has only a 4GB VRAM.

The 21.5" was designed for MXM-A cards so maximum wattage output was 55W. When I had GTX 770M in my iMac it would constantly reboot just doing simple but Airport/Sata intensive tasks. Basically the card was drawing too much from the PSU so when other devices inside needed the resources the iMac would just reboot. Now because I accidently own a 765M i'd figure i'd try it again and see what happens. In Mojave/Catalina I will still have random reboots just not as often because the iMac can just barely handle the 50-75w spikes from the card, but still can randomly reboot when downloading something large like downloading an ISO file, and then minimizing the Safari window. I have only 2 SSD's in my system plus the original Optical drive, so no HDD's on the 12V rail for me. Also you're only on a core i5 I have an i7 2600s which could make the situation worse. The TLDR is the PSU in the 21.5" iMac can't handle the larger MXM-B card. This should be linked on page 1. Tell you what. I'll go post some heaven/valley benchmarks and we can compare them together. I think your i5 could actually be the bottleneck.

Thanks! I've never actually had it reboot unintentionally, even with a very graphics-intensive game running, youtube videos playing, and a flash game running. I've got the original 500GB HDD and a 500GB SSD in there too...

If it's just a power issue, would an 880M work in a 27" iMac? I could probably just get a used 27" PSU and put it in. That would (according to the numbers at least) give me the wattage for an i7-3770 and an 880M, plus everything else.

In activity monitor, the CPU sits at about 25% utilization when running FS19 and a few other apps. With youtube and/or flash-based games running too is where it suffers. Would it still be a bottleneck even if it isn't at 100% utilization?

I saw way back in the thread that someone got an 880M working by just using a slightly modified 780M bootscreen fix. As far as I can see, the 880M is just a slightly higher-clocked 780M with extra memory. Is that right, or is there more to it than that?

I'll have to install the stuff to do those benchmarks. I haven't done them before.

Edit: As a complete novice to the world of benchmarking (I've seen and compared them before, never done one myself), I've got a question: Do I close activity monitor or not? I've already closed all other apps. For reference, I always have it running while I am using the computer. Also, what should I do with my fan settings? Put them to Apple's default, or leave my aggressive settings in Macs Fan Control?

Edit 2: What settings should I put the benchmarks to? Don’t our settings have to be the same to let us really compare the numbers?

 

[tgaillar]

Edit: While I'm at it, is it worth replacing the CPU and/or PSU as well? I would only do the PSU if I had to for wattage reasons, but I would love more CPU power. The CPU in the machine currently is an i5-2400S. I was thinking of an i7-3770. Does anyone have thoughts/suggestions on that front?

That would have been a Core-i7 3770S for a 21.5" iMac (65W TDP limitation)!

No, it will not work *at all* (I tested and confirmed a no-boot issue with a Core-i7 3770S in both 21.5" & 27"2011 iMacs, many others MR folks tried as well with the same outcome)! Reason (likely) is BIOS enforces Sandy-Bridge CPU, thus not accepting Ivy-Bridge CPUs even if socket is compatible (a fate many PC mobo endured until they got a BIOS update -- feel free to cook an updated BIOS...).

 

[limmers2015]

That would have been a Core-i7 3770S for a 21.5" iMac (65W TDP limitation)!

No, it will not work *at all* (I tested and confirmed a no-boot issue with a Core-i7 3770S in both 21.5" & 27"2011 iMacs, many others MR folks tried as well with the same outcome)! Reason (likely) is BIOS enforces Sandy-Bridge CPU, thus not accepting Ivy-Bridge CPUs even if socket is compatible (a fate many PC mobo endured until they got a BIOS update -- feel free to cook an updated BIOS...).

Ok. What’s the best I’ll be able to get for a CPU then?
I did mean the 3770, not the 3770S. If it worked, I would’ve been fine with being 12W over spec.

 

[highvoltage12v]

Thanks! I've never actually had it reboot unintentionally, even with a very graphics-intensive game running, youtube videos playing, and a flash game running. I've got the original 500GB HDD and a 500GB SSD in there too...

If it's just a power issue, would an 880M work in a 27" iMac? I could probably just get a used 27" PSU and put it in. That would (according to the numbers at least) give me the wattage for an i7-3770 and an 880M, plus everything else.

In activity monitor, the CPU sits at about 25% utilization when running FS19 and a few other apps. With youtube and/or flash-based games running too is where it suffers. Would it still be a bottleneck even if it isn't at 100% utilization?

I saw way back in the thread that someone got an 880M working by just using a slightly modified 780M bootscreen fix. As far as I can see, the 880M is just a slightly higher-clocked 780M with extra memory. Is that right, or is there more to it than that?

I'll have to install the stuff to do those benchmarks. I haven't done them before.

Edit: As a complete novice to the world of benchmarking (I've seen and compared them before, never done one myself), I've got a question: Do I close activity monitor or not? I've already closed all other apps. For reference, I always have it running while I am using the computer. Also, what should I do with my fan settings? Put them to Apple's default, or leave my aggressive settings in Macs Fan Control?

Edit 2: What settings should I put the benchmarks to? Don’t our settings have to be the same to let us really compare the numbers?

Here are the benchmarks for both heaven and valley at 1080p full screen, medium. You really should be keeping your fans at a higher RPM because Apple's stock speeds will cook the 765M fast. Did you apply the correct K5 PRO Viscous thermal paste to the VRAM chips, and other components (well the edges of them, wrong heatsink used) for proper cooling? You really need hyper-threading if you're trying to game with such an old CPU even more so because its a down-clocked version of the i5-2500. Please don't attempt a larger card in this iMac especially if you never increased the fan speeds before. If a 780M ROM was installed onto an 880M it will boot, they have the same DIE, however i'm unsure if all 8gb of VRAM will be recognized.
[automerge]1588867467[/automerge]

Ok. What’s the best I’ll be able to get for a CPU then?
I did mean the 3770, not the 3770S. If it worked, I would’ve been fine with being 12W over spec.

i7-2600S the "S" is the important part. It's a down-clocked version of the 2600. The 21.5" iMac only allows for "S" SKU CPU's.

The best/cheapest option is to buy an HP like this https://www.ebay.com/itm/HP-Compaq-...2-80GHz-8GB-RAM-500GB-HDD-DVD-RW/402252403852 and swap the CPU with yours. You can then re-use the HP as a light web browser or resell it for virtually the same pice.

 

[tgaillar]

Ok. What’s the best I’ll be able to get for a CPU then?
I did mean the 3770, not the 3770S. If it worked, I would’ve been fine with being 12W over spec.

No, it would not (21.5" BIOS enforces 65W TDP limit -- not sure how, though)!
Your next best option for a (likely cheaper) 4c/8t CPU is Xeon E3-1260L / Xeon E3-1265L (both 45W, again the only 2 below the 65W TDP limit...)

EDIT: and yes, highvoltage12v is right, 2600S of course

 

[highvoltage12v]

No, it would not (21.5" BIOS enforces 65W TDP limit -- not sure how, though)!
Your next best option for a (likely cheaper) 4c/8t CPU is Xeon E3-1260L / Xeon E3-1265L (both 45W, again the only 2 below the 65W TDP limit...)

EDIT: and yes, highvoltage12v is right, 2600S as well

until I test a Xeon for myself... I was talking with @StephN999 who is running a xeon with no IGPU in a 2011 model, which prevents the machine from waking from sleep. A sad issue unfortunately, I was hoping the 2011 models could be upgraded to a Xeon and wake from sleep perfectly with no additional kexts for the IGPU, oh well.

 

[limmers2015]

Here are the benchmarks for both heaven and valley at 1080p full screen, medium. You really should be keeping your fans at a higher RPM because Apple's stock speeds will cook the 765M fast. Did you apply the correct K5 PRO Viscous thermal paste to the VRAM chips, and other components (well the edges of them, wrong heatsink used) for proper cooling? You really need hyper-threading if you're trying to game with such an old CPU even more so because its a down-clocked version of the i5-2500. Please don't attempt a larger card in this iMac especially if you never increased the fan speeds before. If a 780M ROM was installed onto an 880M it will boot, they have the same DIE, however i'm unsure if all 8gb of VRAM will be recognized.
[automerge]1588867467[/automerge]

i7-2600S the "S" is the important part. It's a down-clocked version of the 2600. The 21.5" iMac only allows for "S" SKU CPU's.

The best/cheapest option is to buy an HP like this https://www.ebay.com/itm/HP-Compaq-...2-80GHz-8GB-RAM-500GB-HDD-DVD-RW/402252403852 and swap the CPU with yours. You can then re-use the HP as a light web browser or resell it for virtually the same pice.

Ok. Running benchmarks now. I was stupid, and only had the old thermal paste and other cooling stuff handy, so that’s all the card has. I do run with very aggressive fan speeds. I’ll leave all other settings at the defaults for medium. Tesselation off, Stereo 3D off, antialiasing x2. I will turn vsync on though.
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No, it would not (21.5" BIOS enforces 65W TDP limit -- not sure how, though)!
Your next best option for a (likely cheaper) 4c/8t CPU is Xeon E3-1260L / Xeon E3-1265L (both 45W, again the only 2 below the 65W TDP limit...)

EDIT: and yes, highvoltage12v is right, 2600S of course

Would an i7-2600S be a major enough improvement over my i5-2400S to be worth doing?

 

[highvoltage12v]

Would an i7-2600S be a major enough improvement over my i5-2500S to be worth doing?

Your benchmarks should somewhat answer the question.

 

[limmers2015]

Here are the benchmarks for both heaven and valley at 1080p full screen, medium. You really should be keeping your fans at a higher RPM because Apple's stock speeds will cook the 765M fast. Did you apply the correct K5 PRO Viscous thermal paste to the VRAM chips, and other components (well the edges of them, wrong heatsink used) for proper cooling? You really need hyper-threading if you're trying to game with such an old CPU even more so because its a down-clocked version of the i5-2500. Please don't attempt a larger card in this iMac especially if you never increased the fan speeds before. If a 780M ROM was installed onto an 880M it will boot, they have the same DIE, however i'm unsure if all 8gb of VRAM will be recognized.
[automerge]1588867467[/automerge]

i7-2600S the "S" is the important part. It's a down-clocked version of the 2600. The 21.5" iMac only allows for "S" SKU CPU's.

The best/cheapest option is to buy an HP like this https://www.ebay.com/itm/HP-Compaq-...2-80GHz-8GB-RAM-500GB-HDD-DVD-RW/402252403852 and swap the CPU with yours. You can then re-use the HP as a light web browser or resell it for virtually the same pice.

Alright. I have results. Kept my aggressive fans on the whole time, also had activity monitor showing CPU and GPU. Macs Fan Control showed temperature as well. Temps were about the same as when I play FS19, around 170F on the GPU PECI and 130F on the GPU heatsink. Didn't look at the CPU temps, but that fan didn't even really ramp up, so they definitely stayed pretty low. GPU showed 100% utilization, CPU sat at about 30%.

There are two other things that I noticed.
1. The GPU PECI temp was jumping around very rapidly, while the GPU heatsink temp just rose slowly. This makes me suspect my recycled thermal paste even more...
2. I just noticed that, in both benchmarks, my GPU was classed as having only 256MB of VRAM. Looking back at your benchmarks, @highvoltage12v, it says the correct 2048 MB of VRAM. Is this just a Unigine problem, or is my card actually reporting and using only 1/8 of its VRAM? I don't know. My computer says 2047 MB, which makes me think that it is just a Unigine issue...

 

[highvoltage12v]

In both instances your benchmarks result in half of what my iMac scores. So something is wrong here. Either Hyperthreading makes a huge difference. Your ram config is wrong (not in multichannel mode) or your card is severely throttled down because you didn't use new thermal paste and some parts of your Die are very hot. Unfortunately I'd like you to fix your thermal paste and flash your card to continue investigating what the issue could be.

170F is hot about 76C my card usually sits at 68C when benchmarking, please do things properly for the sake of that card.

 

[limmers2015]

In both instances your benchmarks result in half of what my iMac scores. So something is wrong here. Either Hyperthreading makes a huge difference. Your ram config is wrong (not in multichannel mode) or your card is severely throttled down because you didn't use new thermal paste and some parts of your Die are very hot. Unfortunately I'd like you to fix your thermal paste and flash your card to continue investigating what the issue could be.

The computer doesn't report whether or not it is in multi-channel mode for RAM, but I doubt that it is a RAM issue. It's two pairs of matched sticks, in the correct slots to be used in dual-channel mode.

It could be hyperthreading, but that doesn't seem to fit (to me at least) with the only 30% utilization of the CPU.

It probably is the card throttling. 😞 I'll get some of the good stuff and redo it.

What's the best stuff to use in your opinion? I've heard great things about "Thermal Grizzly Kryonaut" and "Arctic MX-4".

What I'm less sure about is the "paste" to use with the VRAM chips and other assorted components that don't fit well to the heatsink. Should I just get a 27" heatsink? Would that line up better with the MXM-B card? I could also get some smaller heatsinks and put them on the chips individually.

Apple was dumb, and didn't give the GPU it's own fan, so it's up to the optical drive fan to cool the GPU as well. The air goes right past the card on its way to the GPU heatsink, so anything right on the card would get cooled too. (just for those who don't know, I'm sure you do).

As far as flashing the card with the correct VBIOS, I should just follow the methods in the original post, right? Do you think that doing it via Linux will work, or will I probably have to get/make a direct programmer like is shown in the OP? I fundamentally refuse to pay Microsoft or Google for anything, and my parents won't let me pirate a copy of Windows, so I'm stuck with Linux or direct. The only non-MacOS machine in our house still runs XP, and PCI instead of PCIe slots...

While I'm doing all of this, what are your thoughts on just 3D-printing a "shelf" for the back of the thing, and mounting the GPU out there with proper cooling via a PCIe extension? Worth it? I wonder if I might not have issues getting a compatible card that is not MXM, and would therefore have a proper cooler on it. I might still have to get a MXM card, and try to find a cooler that fits it properly outside the iMac...

Does a more powerful Kepler-based card than an 880M even exist (regardless of whether it is MXM or not)?

 

[tgaillar]

until I test a Xeon for myself... I was talking with @StephN999 who is running a xeon with no IGPU in a 2011 model, which prevents the machine from waking from sleep. A sad issue unfortunately, I was hoping the 2011 models could be upgraded to a Xeon and wake from sleep perfectly with no additional kexts for the IGPU, oh well.

Well, we should (likely) be in luck, then, as Xeon E3-1260L / Xeon E3-1265L both have an IGP (expecting the same as for the Xeon L3426 in your 21.5")

PS: and so are Xeon E3-12x5 for a 27" version (ending "5" denotes IGP, to be confirmed, though -- not to mention they are not cheap, usually)

 

[limmers2015]

In both instances your benchmarks result in half of what my iMac scores. So something is wrong here. Either Hyperthreading makes a huge difference. Your ram config is wrong (not in multichannel mode) or your card is severely throttled down because you didn't use new thermal paste and some parts of your Die are very hot. Unfortunately I'd like you to fix your thermal paste and flash your card to continue investigating what the issue could be.

170F is hot about 76C my card usually sits at 68C when benchmarking, please do things properly for the sake of that card.

I am trying to. Obviously I didn't do good enough of a job with my initial install, due to my use of recycled thermal paste. I hate seeing hardware destroyed as least as much as the next person does...

Edit: I'm going to try flashing with nick's VBIOS for the 765M first, and see what difference that makes.

Any advice on what works and what doesn't to flash the VBIOS? Supposedly "brew install flashrom" is a way to go, but there's also @xanderon 's linux "tool", and the @jowaju 's minimal windows 7 partition method. Which of these is the best way to go? I could get a CH134a, put the old 6750M back in, and flash the VBIOS that way, but that's much more work. Since I've already got the card working, and can boot with it, I think that one of the software only tools is probably a better option for me.

I'll also order the proper thermal paste and other goodies, so I can fix my original hack job ASAP. I'm leaning towards Thermal Grizzly's Kryonaut for the die itself, plus some thermally conductive pads for the VRAM chips and anything else that needs cooling, and some small aluminum heatsinks for the chips on the other side of the board from the heatsink proper. I’ll make sure to get a bunch, as I did up my brother’s iMac exactly the same as mine, just about 2 weeks later and with a smaller SSD. He’ll end up needing a thermal redo at least, and I’ll try and talk him into a VBIOS flash too, as I’ll test everything on my iMac first. Until then, I’ll just let him know that he has to set his fans a lot more aggressively.

Unfortunately, my parents won't let me take the computer back apart (to fix the bad cooling) or try the VBIOS reflash until the school year is over, as this is my only computer (We have others, but they are all daily-drivers for other people in our house, and not really share-able in the way I would need access to it for schoolwork).

Fortunately, I'm homeschooled, and all I have left of my school year is my self-taught history and English. I'm going to see if I can get a semester of work done in about 2 weeks, so I can be back to working on this by the end of May. Until then, I'm just going to further increase the aggressiveness of my fan settings, and continually monitor the GPU temps whenever I am doing anything GPU-intensive.

Tl;Dr: Going to try VBIOS, then fix cooling, just so I have an idea of which one is the bigger issue for performance. Personal issues are interfering in that process. Should be able to do both steps in about 2 weeks time.

 

[Rhino_60]

Sorry, but I believe your analysis is not correct. Your old winbond BIOS chip was listed in my flashrom v1.1 software so it will be in your version v1.18. You have just not managed to seat the clip or configure the CH341A at all. Reading the BIOS works with a correct setup and carefully seated clip Hope you get it done - you are close!

Hi,
today I've tried for many hours to position in right mode my clip programmer but ... without success!
Just to be sure: when you connect ch341a only the red led is on (power) and "run" led is off ?

... Maybe I've a wrong version of software, but I haven't found in my database the W25x20CLNIG, I've found only W25x20, could you please send me your software ?

Last chance for update my iMac is to create an USB drive for flash my card with reboot iMac by linux nvflash after fitting video card and new CPU (i7 2600s).

 

[highvoltage12v]

Hi,
today I've tried for many hours to position in right mode my clip programmer but ... without success!
Just to be sure: when you connect ch341a only the red led is on (power) and "run" led is off ?

... Maybe I've a wrong version of software, but I haven't found in my database the W25x20CLNIG, I've found only W25x20, could you please send me your software ?

Last chance for update my iMac is to create an USB drive for flash my card with reboot iMac by linux nvflash after fitting video card and new CPU (i7 2600s).

If the red LED turns off at all while connected that means something is shorted.

 

[nathansz]

I want to buy a 780. the Ali store I bought my 770 from seems to have disappeared. wondering if anyone can point me to a source they've had success with. thanks