A list of successful iMac 27" (2012-2019) SSD upgrades

[mbosse]

A few things here I'd like to note:

1. Heatsink:

With so little space, I want as much air movement as possible. Reduced air space limits efficient cooling. I understand airflow is a more important factor for heat dispersal than total heatsink surface area (fins). It is airflow which is essential for removing radiated heat. A greater volume and faster movement of air = greater heat dispersal and a cooler running SSD or chip, fins or no fins. That is my opinion. The flat copper helps absorb heat from the controller and diffuse it more evenly throughout the heatsink. Fan then blows excess radiant heat away from the copper heatsink thus preventing heat build up in the NVMe operation. Generally, when NVMe temperature rises to 75° or above (depending on each models design tolerance), NVMe will throttle back to avoid damage.

Excellent reasoning on using copper instead of the usual aluminium heat sinks, as copper has roughly twice the conductivity coefficient than (most) aluminium alloys. What would interest me would be the actual reduction in temperature with/without copper heatsink with no interference by Macs Fan Control etc., because I am not entirely convinced about your statement that airflow is more important than heatsink surface: This is because the airflow reduces temperature because it flows over the surfaces to be cooled, the higher the touched surface the higher hence the heat removal. And here the fins serve to enlarge the available surface area such that the net effect between a flat copper heatsink vs. the commercial aluminium heatsink with fins could be actually identical.

Really curious!

2. Fan control software:
There is absolutely no need to use such as macOS perfectly reads the temperature from the NVMe SSD. Fan control software was necessary back in the 2009 - 2011 days of iMacs when Apple used (i) special versions of HDDs with a separate connector for a temperature data cable (2009/2010) or (ii) special firmware on their HDDs. Vendors like OWC offered (expensive) special cables with temperature sensor. Fun fact: for the 2009/2011 iMacs one could easily use a €2 Apple DVD Drive temperature cable to reinstate perfect temperature reading from any HDD/SSD, just the 2011 iMac absolutely needed the OWC cable if a third-party drive would be use. No such drive cable or fan control software is needed for the slim 2012 or later iMacs for any of the SSDs confirmed to be compatible.

If you want to achieve lower than the macOS-set temperature range at the cost of some additional noise then of course you can resort to fan control software.

3. Migration from TM backup of FusionDrive:

Also, did anyone make a Fusion drive clone before the drive replacement? If yes, please let me know how it works, since I do not want to make a clean installation on a new drive because I would like to install Sonoma from scratch via OCLP some time after the upgrade, restore the backup via Time Machine (if it would be possible, of course) and upgrade OS to Sequoia (since the restoration does not work on Sequoia properly according to OCLP website). And I do not want to make some extra steps during or right after the upgrade, so I can have some time to test the updated hardware.

In terms of migration and TM there is no difference between a FusionDrive or a normal HDD/SSD. You can migrate from or to a FusionDrive just like a normal drive provided the available drive space allows and the target macOS is the same version or younger. For purposes of macOS backup and migration, a FusionDrive is seen just like a standard drive.

BTW, @Terraaustralis, Howard Oakley does no longer recommend full macOS install and then migration later - he does it now directly at setup: https://eclecticlight.co/2024/11/12/migrating-to-a-new-mac-and-claiming-time-machine-backups/

Cheers and good luck to all!

 

[Terraaustralis]

Diagnostic light won’t tell him what the issue is regarding audio. Likely issue is due to the headphone port not being recognised and the cable being damaged during disassembly

Understood mbosse.
Read my remarks of Monday 11.15 and you will appreciate the context of my comments.
Cheers,

 

[mbosse]

Understood mbosse.
Read my remarks of Monday 11.15 and you will appreciate the context of my comments.
Cheers,

Are you mixing up replies? I did not comment on the diagnostic lights... ;-)

 

[Terraaustralis]

Diagnostic light won’t tell him what the issue is regarding audio. Likely issue is due to the headphone port not being recognised and the cable being damaged during disassembly

That is understood TwoH.
See my original post of Monday at 11.55 to understand context.
Cheers

 

[TwoH]

That is understood TwoH.
See my original post of Monday at 11.55 to understand context.
Cheers

Always appreciate extra ideas from people and I apologise I missed your initial post regarding it.
I hope we can get an update from OP regarding his issue to know if there has been any change and/or further diagnosing of the issue.

I do think we can interpret from their post of the machine's sound not working that they are able to POST and boot fine into their machine, and we are purely looking at a sound-related issue, to which I think we are both correct in looking towards the headphone port being the issue - either due to not being seated correctly or due to damage on the actual cable itself.

But we are eagerly awaiting any further information from OP to know for certain!

 

[Terraaustralis]

Are you mixing up replies? I did not comment on the diagnostic lights... ;-)

I am indeed! just saw the mbosse ‘like’ while scanning. My apologies.

A few things here I'd like to note:

1. Heatsink:



Excellent reasoning on using copper instead of the usual aluminium heat sinks, as copper has roughly twice the conductivity coefficient than (most) aluminium alloys. What would interest me would be the actual reduction in temperature with/without copper heatsink with no interference by Macs Fan Control etc., because I am not entirely convinced about your statement that airflow is more important than heatsink surface: This is because the airflow reduces temperature because it flows over the surfaces to be cooled, the higher the touched surface the higher hence the heat removal. And here the fins serve to enlarge the available surface area such that the net effect between a flat copper heatsink vs. the commercial aluminium heatsink with fins could be actually identical.

Really curious!

2. Fan control software:
There is absolutely no need to use such as macOS perfectly reads the temperature from the NVMe SSD. Fan control software was necessary back in the 2009 - 2011 days of iMacs when Apple used (i) special versions of HDDs with a separate connector for a temperature data cable (2009/2010) or (ii) special firmware on their HDDs. Vendors like OWC offered (expensive) special cables with temperature sensor. Fun fact: for the 2009/2011 iMacs one could easily use a €2 Apple DVD Drive temperature cable to reinstate perfect temperature reading from any HDD/SSD, just the 2011 iMac absolutely needed the OWC cable if a third-party drive would be use. No such drive cable or fan control software is needed for the slim 2012 or later iMacs for any of the SSDs confirmed to be compatible.

If you want to achieve lower than the macOS-set temperature range at the cost of some additional noise then of course you can resort to fan control software.

3. Migration from TM backup of FusionDrive:



In terms of migration and TM there is no difference between a FusionDrive or a normal HDD/SSD. You can migrate from or to a FusionDrive just like a normal drive provided the available drive space allows and the target macOS is the same version or younger. For purposes of macOS backup and migration, a FusionDrive is seen just like a standard drive.

BTW, @Terraaustralis, Howard Oakley does no longer recommend full macOS install and then migration later - he does it now directly at setup: https://eclecticlight.co/2024/11/12/migrating-to-a-new-mac-and-claiming-time-machine-backups/

Cheers and good luck to all!

Hi mbosse,

Heatsink thoughts:
I entirely agree with your considerations regarding cooling radiant solids such as heatsink. Only a test can tell us the best balance between air flow and radiant surface area. Not an easy test to configure.

As any mechanic knows with a motor vehicle radiator, increased surface area increases exposure to wind pressure and disperses heat to cool water - and therebye, engine temperature. However for the iMac, the passage of air in the restricted interior between iMac back and NVMe heatsink suggests to me that greater heatsink surface (fins), simultaneously obstruct airflow which is not adequately compensated for with increased air flow speed due to turbulence. Therefore, I suspect heat dispersion would be less efficient.

Alternatively It can be argued in the reverse: That if given air pressure from a fan source remains constant, the physical restriction of fins will create a faster air flow for the same volume of air over the heatsink therebye removing heat more efficiently. The determinant is how airflow actually behaves in the circumstances of the iMac.

Perhaps I favour free airflow in volume because I enjoy sailing and understand something about lift and the passage of a hull through water. That is in no way parallel to our heatsink except regarding turbulance. Whether air or water, turbulance reduces efficiency. How significant that is with our heatsink is an open question. I welcome comments.

In practice, the saving grace is the SN770 being a PCIe 4.0 NVMe working at PCIe 3.0 speeds. So heat cannot build up to a critical level in the Intel iMac.

Fan Control Software:
Thank you for the information. I appreciate your comments. I have taken the subject of fan temperatures at face value while asking myself how efficient are these fan readings actualy are. Being software, I assume they are derived from the iMac OSX sensors and data.

However, I would you care to expand upon ‘need’. Does that mean that for any post 2011 iMac I can trash Macs Fan Control and rely entirely on Apple? When I use a more powerful NVMe than the small Apple supplied SSD’s I would expect to be pushing or even exceeding Apples’ built in temperature tolerances. If this is so it would seem reasonable to increase cooling via fan control software?

Howard Oakley:
I shall have to send Howard a stiff reprimand for changing tack! - Joke.

Thanks for your time mbosse. always something to learn from you.

 

[Terraaustralis]

Always appreciate extra ideas from people and I apologise I missed your initial post regarding it.
I hope we can get an update from OP regarding his issue to know if there has been any change and/or further diagnosing of the issue.

I do think we can interpret from their post of the machine's sound not working that they are able to POST and boot fine into their machine, and we are purely looking at a sound-related issue, to which I think we are both correct in looking towards the headphone port being the issue - either due to not being seated correctly or due to damage on the actual cable itself.

But we are eagerly awaiting any further information from OP to know for certain!

Yes. From what I could make out he was upgrading for a client which leads to a very difficult situation. I hope a replacement audio cable is the solution. I was concerned that his logic board may be damaged, hence my remarks.