Apple seems to have dodged a bullet in going with their own Silicon

[pshufd]

The final 27" Intel iMac design, the Retina iMac, ran from late 2014–2020. The iMac Pro wasn't introduced until late 2017, so I can understand why they didn't want to redesign the Retina iMac at that time.

But what I can't understand is why they didn't give the 27" Retina iMac a better cooling system to start with. Apple understands the value of keeping noise levels low, and they knew the single-fan design wasn't sufficient to cool the iMac under heavy load without being loud. The added expense of a second fan, some extra plastic ducting, and a larger heatsink would have been small, and would have required only a small increase in case thickness. All of this could have been easily accommodated within a desktop AIO design, as evidenced by the iMac Pro. I think this was a design failure on Apple's part.

To those who want to suggest that maybe Apple designed the 27" Retina iMac to operate quietly with the chips it originally came with, but didn't anticipate a subsequent increase in TDPs: That's not what happened here. The maximum TDP of the first 27" Retina iMac was 983 BTU. That was greater than that of any subsequent iMac except for the 2020 10-core i9, and even that one was only marginally (2.4%) higher: 1,007 BTU. So if they had simply designed the 27" Retina iMac to operate quietly with the Y1 chipset, it would have been quiet for all subsequent model years.

iMac power consumption and thermal output - Apple Support

Learn about the power consumption and thermal output (BTU) of iMac computers.

support.apple.com

A rather interesting side-discussion. I had an 2014 i7 iMac 27 and it ran on the hot and noisy side. I have a 2015 i5 iMac 27 and it runs cool and quiet. I also have an iMac Pro and the average run temperature is about 10 degrees hotter (around 50 degrees), but it's always quiet. The iMac Pro can do considerably more work than the older iMacs.

Update: I just went through the power numbers in your link and it reflects my observations between the 2014 and 2015 models.

 

[theorist9]

A rather interesting side-discussion. I had an 2014 i7 iMac 27 and it ran on the hot and noisy side. I have a 2015 i5 iMac 27 and it runs cool and quiet. I also have an iMac Pro and the average run temperature is about 10 degrees hotter (around 50 degrees), but it's always quiet. The iMac Pro can do considerably more work than the older iMacs.

It makes sense your 2015 i5 runs quieter than your 2014 i7, since Apple lists their thermal ouputs as 673 BTU/h and 983 BTU/h, respectively.

I have the 2019 i9 (895 BTU/h), and it can get noisy.

AS of course makes managing thermal output a lot easier for Apple.

 

[pshufd]

It makes sense your i5 runs quieter than your i7, since the former should have a lower TDP. [I'm assuming your i5 also has a less power-hungry GPU than your i7; as you know, the GPU is a big contributor to thermal output.]

I have the 2019 i9, and it can get noisy.

AS of course makes managing thermal output a lot easier for Apple.

The table has the Max TDP of the 2015 i7 at 240 watts and the Max TDP of the 2014 i7 at 288 watts. So the power consumption is significantly higher from maxed 2015 to maxed 2014. My 2015 was a base model upgraded to 32 GB of RAM. The 2014 had the i7, top-end GPU, SSD and 32 GB of RAM.

I didn't know that the iMac Pro has dual fans compared single for the iMac 27.

 

[theorist9]

I didn't know that the iMac Pro has dual fans compared single for the iMac 27.

Yeah, that's the key difference between their cooling systems. iMac on L, iMac Pro on R. Note all the empty space in the iMac that could have been used to accommodate dual fans. And it wouldn't need to have been as beefy as that in the iMac Pro, since the latter's max thermal output was 1,262 BTU/h.

Closeup of iMac Pro dual fans:

 

[PaulD-UK]

The iMacs single fan wasn’t the problem.
The iMac Pro has ~4x the heat exchange volume and about 4x the heat pipe cross section - for about +40% more heat dissipation.
To have cooled the iMac properly would have meant moving the RAM away from the CPU, losing the RAM hatch…

 

[theorist9]

The iMacs single fan wasn’t the problem.
The iMac Pro has ~4x the heat exchange volume and about 4x the heat pipe cross section - for about +40% more heat dissipation.
To have cooled the iMac properly would have meant moving the RAM away from the CPU, losing the RAM hatch…

That's the first time I've heard the argument that it wasn't possible to adequately cool the iMac while maintaining a RAM hatch. Is that reallly the case? I'm skeptical of the idea that their engineers could not have figured out some way to do this.

It's possible they didn't include a RAM hatch on the iMac Pro for business reasons--that they wanted their Pro customers to buy their RAM from Apple, rather than buying a min-spec model and immediately upgrading the RAM.

 

[PaulD-UK]

The iMac Pro is the way it is because of engineering reasons and Ive’s design philosophy.
I’m sure the Mac Pro design team did it between MP 6,1 and 7,1.
The iMac’s logic board is too squeezed up to allow the necessary heat dissipation.

The iMac Pro team solved that and probably tripled the fundamental build cost of the design.

 

[theorist9]

The iMac’s logic board is too squeezed up to allow the necessary heat dissipation.

The iMac Pro team solved that and probably tripled the fundamental build cost of the design.

There's no reason Apple couldn't have designed the iMac's logic board differently, had such been needed in order to accommodate better cooling.

I hardly think an extra fan and some added ducting would triple the build cost!

Apple has both single-fan and dual-fan versions of the current AS iMac.

 

[pshufd]

The iMac Pro is the way it is because of engineering reasons and Ive’s design philosophy.
I’m sure the Mac Pro design team did it between MP 6,1 and 7,1.
The iMac’s logic board is too squeezed up to allow the necessary heat dissipation.

The iMac Pro team solved that and probably tripled the fundamental build cost of the design.

It's great buying them on the used market. The base model was $5k and those are selling for $600 - $800 now.

It would be nice to add RAM but the base model starting at 32 GB was probably good enough for the vast majority of customers.

 

[mr_roboto]

To those who want to suggest that maybe Apple designed the 27" Retina iMac to operate quietly with the chips it originally came with, but didn't anticipate a subsequent increase in thermal output: That's not what happened here. The max thermal output of the first 27" Retina iMac was 983 BTU/h. That was greater than that of any subsequent iMac except for the 2020 10-core i9, and even that one was only marginally (2.4%) higher: 1,007 BTU/h. So if they had simply designed the 27" Retina iMac to operate quietly with the Y1 chipset, it would have been quiet for all subsequent model years.

iMac power consumption and thermal output - Apple Support

Learn about the power consumption and thermal output (BTU) of iMac computers.

support.apple.com

I think these maximum output numbers are misleading you.

What got worse for the 27" Retina chassis from 2014 to 2020 was that Intel got stuck on their 14nm process node. Intel's margins relied on delivering a new "generation" with a performance gain every year, and in order to keep that happening while their process tech stagnated, they began to permit individual cores to pull more and more power.

The reason this didn't affect maximums much is that it was an oversubscription model. If you multiplied the peak power per core by the number of cores, you'd get a number way above the processor's nominal TDP, but as more cores came online the "Turbo" power controller would reduce clock speeds to keep total package power under control.

So, a 2020 Intel chip will rocket up to its TDP limit with a lot fewer active threads than a 2014 Intel chip. Without an increase in cooling capacity, that made it a lot more common for 27" iMac users to experience noisy fans.

Basically, Apple didn't design the 2014 iMac chassis to handle max load quietly. It was designed to handle low loads in virtual silence and medium loads with reasonable fan noise. But Intel kept moving the bar for low and medium loads up, and Apple didn't change the iMac's cooling, so 27" iMacs kept getting noisier.

 

[theorist9]

I think these maximum output numbers are misleading you.

What got worse for the 27" Retina chassis from 2014 to 2020 was that Intel got stuck on their 14nm process node. Intel's margins relied on delivering a new "generation" with a performance gain every year, and in order to keep that happening while their process tech stagnated, they began to permit individual cores to pull more and more power.

The reason this didn't affect maximums much is that it was an oversubscription model. If you multiplied the peak power per core by the number of cores, you'd get a number way above the processor's nominal TDP, but as more cores came online the "Turbo" power controller would reduce clock speeds to keep total package power under control.

So, a 2020 Intel chip will rocket up to its TDP limit with a lot fewer active threads than a 2014 Intel chip. Without an increase in cooling capacity, that made it a lot more common for 27" iMac users to experience noisy fans.

Basically, Apple didn't design the 2014 iMac chassis to handle max load quietly. It was designed to handle low loads in virtual silence and medium loads with reasonable fan noise. But Intel kept moving the bar for low and medium loads up, and Apple didn't change the iMac's cooling, so 27" iMacs kept getting noisier.

Except that even the early Retina iMac models were reported to be noisy under load, such as pshufd's 2014 i7. So it doesn't appear that fan noise was something that only crept up on Apple years after they released the machine.

More broadly, a key part of Apple's target market were those doing 4k video work--that was a large part of the idea behind the 5k: To allow people to display 4k natively while also being able to display the menu and control items. I'd imagine that 4k video processing could heavily load both the CPU and GPU, indicating that fan noise at the machine's normal max capacity (whatever that was down-regulated to be) should have been accounted for in Apple's thermal design.

 

[iPadified]

The final 27" Intel iMac design, the Retina iMac, ran from late 2014–2020. The iMac Pro wasn't introduced until late 2017, so I can understand why they didn't want to redesign the Retina iMac at that time.

But what I can't understand is why they didn't give the 27" Retina iMac a better cooling system to start with. Apple understands the value of keeping noise levels low, and they knew the single-fan design wasn't sufficient to cool the iMac under heavy load without being loud. The added expense of a second fan, some extra plastic ducting, and a larger heatsink would have been small, and would have required only a small increase in case thickness. All of this could have been easily accommodated within a desktop AIO design, as evidenced by the iMac Pro. I think this was a design failure on Apple's part.

To those who want to suggest that maybe Apple designed the 27" Retina iMac to operate quietly with the chips it originally came with, but didn't anticipate a subsequent increase in thermal output: That's not what happened here. The max thermal output of the first 27" Retina iMac was 983 BTU/h. That was greater than that of any subsequent iMac except for the 2020 10-core i9, and even that one was only marginally (2.4%) higher: 1,007 BTU/h. So if they had simply designed the 27" Retina iMac to operate quietly with the Y1 chipset, it would have been quiet for all subsequent model years.

iMac power consumption and thermal output - Apple Support

Learn about the power consumption and thermal output (BTU) of iMac computers.

support.apple.com

I agree, Intel chips has been power hungry for a long time and that has hampered the design of pleasant computers. My 2020 iMac is horrible for compute hungry jobs due to noise, while my M1 Pro MBP is silent for the same jobs. About the same performance.

Apple had the 2017 iMac Pro cooling system available and could have dropped that into the 2020 iMac without much fuzz. it cost money to design cooling systems. Look at the Cu heat sink in the Studio Ultra.

 

[dmccloud]

I am still using 3970 thread ripper. Does what ever I throw at it. Power consumption is much better in 59X.

My current gaming PC runs a Ryzen 9 5900x and a Radeon RX 6700XT GPU. My power consumption under load (e.g., gaming, running the Cinebench burn-in test) is lower than what the 13th and 14th gen pulls when only 1-2 cores are in use and the system jacks up their clock speeds. The more I've learned about the 13th and 14th gen Intel parts, the happier I am about going AMD for my gaming rig.

 

[Boil]

My PC is middle-of-the-road:

• AMD 5900X CPU
• Nvidia RTX 2070 GPU
• 32GB G.Skill Trident Z RAM
• 1TB Sabrent Rocket NVMe 4.0 SSD
• ASUS ROG Crosshair VIII Impact mDTX mobo
• Corsair SF750 Platinum-rated PSU
• Lian Li TU-150 chassis

I need to drop an AMD 6800XT GPU in there and make it a Hackintosh...

Or, I just need to buy an new ASi Mac of some sort, probably a Mn Max Mac Studio...

If Apple could see their way to making a Mn Extreme Mac Pro Cube though...

;^p