2019 iMac - i5 vs i9? Cooling and Throttling?

[Rockadile]

If you simultaneously run Intel Burn Test 2.54 and Furmark GPU stress for several hours, how does it hold up at 5.1 Ghz on air cooling?

https://www.techspot.com/downloads/4965-intelburntest.html
https://geeks3d.com/furmark/

I did a 2hr full system burn in test when I built it three months ago. No problems so far.
Still did a -2 AVX offset for that extra peace of mind stability since this is more for work than gaming.
These Corsair ML fans are similar to Noctua Industrial. Moves a lot of air.
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My custom PC with air cooling goes 4.7 continuous with nh-d15 cooler. Only when I try the stress test tools like Linx then I become uncomfortable (seldom reach 90 degree celcious). So it's possible. 4.7 is base turbo clock without any overclocking and it's doable. all time overclock to 5.3 I decided to not do. But you are right. I don't see anyone using i9 with full turbo in AIO.

Anyhow, back to the topic, I'm quite ok with Apple limiting continuous turbo to 3.8 (aka limit TDP). iMac is all in one, and while the performance is needed, it's famous for stability and silence operation. The i9 in iMac is perfectly meant for this, offering the advertised performance in very stable platform. I'm actually considering buying this iMac as this I Believe is going to be the last iMac before Arm and/or T2 when they do change over.

I definitely crash at 5.3 and 5.2 not stable

Which case are you using?

 

[MandiMac]

Well, everything above the base clock is technically automatic overclocking. Throttling would be the process of being under the base clock. Not reaching the highest Turbo Boost level is not throttling. Case closed.

 

[Abbas]

Well, everything above the base clock is technically automatic overclocking. Throttling would be the process of being under the base clock. Not reaching the highest Turbo Boost level is not throttling. Case closed.

EXACTLY. There’d be fewer arguments if more people understood this.

 

[BigBoy2018]

Well, everything above the base clock is technically automatic overclocking. Throttling would be the process of being under the base clock. Not reaching the highest Turbo Boost level is not throttling. Case closed.

This is why my preference is to get the processor with the higher base clock speed and then use something like turbo boost switcher to turn off turbo boost when I'm doing any long video render or export.

With turbo boost on, the fans run up, but I've discovered these long renders don't actually take any less time.

With turbo boost disabled, the machine stays quieter and cooler and stays at the 3.8ghz clock speed throughout.

To me, turbo boost is a little tweak that helps in very brief actions, and something that basically 'tricks' Geekbench and makes the processor seem faster, but for any extended use, it's the base clock speed that is going to be what you need to key in on.

 

[jinnyman]

I definitely crash at 5.3 and 5.2 not stable

Which case are you using?

I use Corsair Quite 600Q. I plan to change with something that's easier to clean the dust filter. Other than that, the case is quite and modest looking.

 

[JohanCruyff]

This is why my preference is to get the processor with the higher base clock speed and then use something like turbo boost switcher to turn off turbo boost when I'm doing any long video render or export.

With turbo boost on, the fans run up, but I've discovered these long renders don't actually take any less time.

With turbo boost disabled, the machine stays quieter and cooler and stays at the 3.8ghz clock speed throughout.

To me, turbo boost is a little tweak that helps in very brief actions, and something that basically 'tricks' Geekbench and makes the processor seem faster, but for any extended use, it's the base clock speed that is going to be what you need to key in on.

Base clock of the i5 9600K is 3.7GHz (6 cores)
Base clock of the i9 9900K is 3.6GHz (8 cores + HT)

What would you suggest?

 

[Colonel Blimp]

Base clock of the i5 9600K is 3.7GHz (6 cores)
Base clock of the i9 9900K is 3.6GHz (8 cores + HT)

What would you suggest?

Bear in mind that we now have several reports that the i9 in the Early 2019 iMacs actually maintains a consistent 3.8 to 3.9 GHz with all eight cores maxed out under a sustained load, so it seems to be performing above its base clock.

I haven’t yet seen (but then I haven’t looked for) similar tests of the i5. That would be an interesting comparison.

 

[joema2]

My custom PC with air cooling goes 4.7 continuous with nh-d15 cooler. Only when I try the stress test tools like Linx then I become uncomfortable (seldom reach 90 degree celcious). So it's possible. 4.7 is base turbo clock without any overclocking and it's doable. all time overclock to 5.3 I decided to not do. But you are right. I don't see anyone using i9 with full turbo in AIO.

Anyhow, back to the topic, I'm quite ok with Apple limiting continuous turbo to 3.8 (aka limit TDP). iMac is all in one, and while the performance is naeeded, it's famous for stability and silence operation. The i9 in iMac is perfectly meant for this, offering the advertised performance in very stable platform...

It's not just AIO designs that don't use an i9-9900k with the 95W thermal limit disabled. I don't see any commercial manufacturer shipping any i9-9900k air-cooled business-class PC that is configured by default to exceed the 3.8Ghz 95W TDP. Maybe there are some but I haven't found any.

Puget Systems has an air-cooled i9-9900k but I think it ships with the 95W TDP enabled. You can go into the BIOS advanced power settings and set that to 250W or whatever you want -- just like you can overclock it. But I don't think the PC manufacturer would support that.

Some manufacturers like Digital Storm have specialized i9-9900k gaming rigs that they'll overclock from the factory -- but they are all liquid cooled.

If no other manufacturer is shipping an air-cooled i9-9900k business-class PC configured by default and fully supported with an unrestricted thermal limit, then I don't see how Apple is doing anything different with the i9 iMac.

 

[jeremiah256]

I'm in a similar boat to you. I have the 2012 imac as well, and it feels about time to upgrade. Although most of my CPU is for photo editing, given 6 years of upgrades I should see some performance.

I would go with the i9, only because of the 32MB limitation of the i5 that I'm reading about here 64MB of memory would be tasty (3rd party form OWC, of course).

Would have to do the 3Tb fusion. all SSDD is nice, but between photo, video and music I'm close to 2TB as it is in personal storage.

Good initial results for the i9

I may be jumping the gun, but I think in a few years, these iMacs will be positively spoken of in the same way as the 2015 and older MBPs.

 

[adamjackson]

I may be jumping the gun, but I think in a few years, these iMacs will be positively spoken of in the same way as the 2015 and older MBPs.

Need a remind me on this one but I bet you're either very right or horribly wrong. and it's really up to Apple, here.

but I think you're on to something.

 

[BigBoy2018]

Base clock of the i5 9600K is 3.7GHz (6 cores)
Base clock of the i9 9900K is 3.6GHz (8 cores + HT)

What would you suggest?

The extra cores will be a benefit, despite the slightly lower clock speed ASSUMING the processor does not throttle below that clock speed because of heat.

Early reports suggest there isn't much of a heat issue with the i9 so I would tentatively suggest the i9 ATM.
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I may be jumping the gun, but I think in a few years, these iMacs will be positively spoken of in the same way as the 2015 and older MBPs.

I am leaning in that direction as well. These iMacs are as powerful as the case design can manage, and may not have throttling issues.

On top of that:

1) They are upgradeable. The 27 inch with ram (easily) and the SATA drive (more difficult but very doable).

2) They are in the last generation of Macs that will be able to run 32-bit software.

3) They are not burdened with the extra complexity and possible failure point of the T2 chips

4) They have legacy ports, not just USB-C


I haven't bought one since I'm still rocking my 2017 iMac, but I am thrilled Apple released these. Gives me a great upgrade option down the road.

 

[Bboble]

Well, everything above the base clock is technically automatic overclocking. Throttling would be the process of being under the base clock. Not reaching the highest Turbo Boost level is not throttling. Case closed.

EXACTLY. There’d be fewer arguments if more people understood this.

The amount of misinformation on throttling has become overwhelming. Restricting a processor to, say, 95 watts is intentional thermal throttling. Beyond that, from the results I've seen, the i9 is actually hunting around 85 watts after spiking to around 120 watts, with a frequency that is also hunting. This hunting is based on some algorithm that is restricting the full performance of the i9. If temp gets too high, restrict power input. Okay, now power is lower, so the temp goes down, now the power goes back up proportionally. This is throttling, based on some PID loop, and, I've seen no video which doesn't highlight this...

An unthrottled processor in Intel Power Gadget shows as a crisp, straight line. If Apple can dissipate the heat of a processor running at 3.8GHz (above base clock) then they should lock it at this, and advertise accordingly. Presently, they are falsely advertising their products.

The real question, as others have eluded to, is what frequency does the 9600K i5 settle on, as this is also a "95W" processor.

 

[cynics]

Well, everything above the base clock is technically automatic overclocking. Throttling would be the process of being under the base clock. Not reaching the highest Turbo Boost level is not throttling. Case closed.

In the context here throttling (dynamic scaling) is 'thermal throttling' due to exceeding the maximum junction temperature between the die and its case (Tjmax).

Saying a CPU isn't thermal throttling that is literally thermal throttling by its very definition regardless of circumstances (overclock, heat sink fell off, inadequate cooling design, turbo boost, etc) is a bit disingenuous.

Besides you can be leaving a lot of performance on the table. Here is an example of my 2011 ThinkPad t420 fifteen minutes into a CPU stress test. I put in an i7 2640m a couple years ago

CPU specs

Since this is a stress test of all cores we won't see max turbo frequency but there is still additional performance to be had over its base 2.80ghz. Honestly I would be a bit disappointed with a computer/cpu that only met its bare minimum spec.

Excuse the iPhone pic of the screen.

In a laptop it is what it is, however in a desktop your CPU limitations should be its power consumption not bouncing off the limits of nuclear meltdown with the CPU's attempts for self preservation.

 

[iPadified]

I said it before, what is interesting is if the i9 is significantly faster and less noisy compared 2017-i7 in an iMac chassi. It is faster and appears to be more silent.

Comparing CPU performances in different chassis is irrelevant. With that reasoning, an air-cooled desktop CPU in that a HP-Z workstation tower is throttled as it is slower than a overclocked liquid nitrogen cooled CPU sitting in an experimental setup.

 

[Rockadile]

It's not just AIO designs that don't use an i9-9900k with the 95W thermal limit disabled. I don't see any commercial manufacturer shipping any i9-9900k air-cooled business-class PC that is configured by default to exceed the 3.8Ghz 95W TDP. Maybe there are some but I haven't found any.

Puget Systems has an air-cooled i9-9900k but I think it ships with the 95W TDP enabled. You can go into the BIOS advanced power settings and set that to 250W or whatever you want -- just like you can overclock it. But I don't think the PC manufacturer would support that.

Some manufacturers like Digital Storm have specialized i9-9900k gaming rigs that they'll overclock from the factory -- but they are all liquid cooled.

If no other manufacturer is shipping an air-cooled i9-9900k business-class PC configured by default and fully supported with an unrestricted thermal limit, then I don't see how Apple is doing anything different with the i9 iMac.

Puget System benchmarks without manual overclocking CPU so stock Intel Boost setting.

 

[Ethosik]

The amount of misinformation on throttling has become overwhelming. Restricting a processor to, say, 95 watts is intentional thermal throttling. Beyond that, from the results I've seen, the i9 is actually hunting around 85 watts after spiking to around 120 watts, with a frequency that is also hunting. This hunting is based on some algorithm that is restricting the full performance of the i9. If temp gets too high, restrict power input. Okay, now power is lower, so the temp goes down, now the power goes back up proportionally. This is throttling, based on some PID loop, and, I've seen no video which doesn't highlight this...

An unthrottled processor in Intel Power Gadget shows as a crisp, straight line. If Apple can dissipate the heat of a processor running at 3.8GHz (above base clock) then they should lock it at this, and advertise accordingly. Presently, they are falsely advertising their products.

The real question, as others have eluded to, is what frequency does the 9600K i5 settle on, as this is also a "95W" processor.

Wait...they are falsely advertising by having it be higher than what was stated? Apple stress tested these. Probably in their tests is was closer to 3.6 than 3.8. And it says turbo boost up to 5 GHz. Isn’t 3.8 between 3.6 and 5?

Also, almost everyone knows thermal throttling is going below base clock due to heat. NOT achieving a constant 5 GHz no matter how hot it gets and having this not be the case is not the same as thermal throttling.

Turbo boost is always meant to be temporary and if the processor utilization allows. It’s NOT “5 GHz sustained for all time unless thermal throttling occurs”. If that’s the case even my 2015 custom built PC with the Nocura heat sink and fan that still won’t reach full turbo boost for hours on a render is thermal throttling.

 

[Bboble]

Wait...they are falsely advertising by having it be higher than what was stated? Apple stress tested these. Probably in their tests is was closer to 3.6 than 3.8. And it says turbo boost up to 5 GHz. Isn’t 3.8 between 3.6 and 5?

Also, almost everyone knows thermal throttling is going below base clock due to heat. NOT achieving a constant 5 GHz no matter how hot it gets and having this not be the case is not the same as thermal throttling.

Turbo boost is always meant to be temporary and if the processor utilization allows. It’s NOT “5 GHz sustained for all time unless thermal throttling occurs”. If that’s the case even my 2015 custom built PC with the Nocura heat sink and fan that still won’t reach full turbo boost for hours on a render is thermal throttling.

Restricting a processor's power input—by the very definition—is thermal throttling. Furthermore, Intel rates the 9900k as having an all-core boost of 4.7GHz sustained. The 5 GHz rating is for only having 2 cores active. My custom built PC with 9900k sustains 4.7GHz on all cores, at ~75C with the Noctua NH-U14S air cooler, albeit at about 135 watts while running Cinebench.

Interestingly, I've seen that the iMac Pro can dissipate ~135 watts at 85C. Thence, Apple themselves have proven that they could more suitably cool the processor they're advertising. Turbo frequencies are Intel designed to be sustained under load, and, the present i9 iMac has shown it can only sustain a few hundred MHz above base clock of 3.6 GHz, not the 1.1 GHz Intel advertised. Again, if Apple cannot cool Intel's i9 chip to work as designed and marketed, then they need not advertise it as the full Intel chip.

 

[startergo]

if Apple is willing to give us

That is the key word. I see thermal throttling in my 2019 mbp. So definitely Apple is not willing ... ever since the trash can fiasco...

 

[Black Diesel]

So what's the word? Have there been enough tests to show the i9 is performing as advertised and worth the extra money? Is it safe to say if money is not an issue then go with an i9 and vega 48?

Is the general consensus that the early '19 iMacs are a worthy upgrade?

Are there any tests out there that state an i5 might be a better value based on performance/heat/throttling?

 

[BigBoy2018]

Restricting a processor's power input—by the very definition—is thermal throttling. Furthermore, Intel rates the 9900k as having an all-core boost of 4.7GHz sustained. The 5 GHz rating is for only having 2 cores active. My custom built PC with 9900k sustains 4.7GHz on all cores, at ~75C with the Noctua NH-U14S air cooler, albeit at about 135 watts while running Cinebench.

Interestingly, I've seen that the iMac Pro can dissipate ~135 watts at 85C. Thence, Apple themselves have proven that they could more suitably cool the processor they're advertising. Turbo frequencies are Intel designed to be sustained under load, and, the present i9 iMac has shown it can only sustain a few hundred MHz above base clock of 3.6 GHz, not the 1.1 GHz Intel advertised. Again, if Apple cannot cool Intel's i9 chip to work as designed and marketed, then they need not advertise it as the full Intel chip.

This discussion helps confirm my belief that you should just get the imac with the highest BASE processor speed.
Geekbench is deceiving in that it will reflect the top turbo boost speed, which the imac cannot sustain very long in real world use.

 

[Bboble]

So what's the word? Have there been enough tests to show the i9 is performing as advertised and worth the extra money? Is it safe to say if money is not an issue then go with an i9 and vega 48?

Is the general consensus that the early '19 iMacs are a worthy upgrade?

Are there any tests out there that state an i5 might be a better value based on performance/heat/throttling?

I haven't seen enough on the i5 to know. While the i9 is no slouch, it is power hungry, and greatly restricted in the iMac. The i5 is much less power hungry, and will likely not be restrained as much. Curious to know how much...haven't seen this yet in the wild.

If it were my money, I'd start with the Vega, then consider the i9. The Vega architecture is much better and more efficient than the older Polaris. Though, these questions are privy to your specific workflow. I will say that the $400 premium for the i9 isn't bad at all, considering it's ~$250 Intel retail difference. Though, I have a hard time putting down money for something I'm not entirely getting.
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This discussion helps confirm my belief that you should just get the imac with the highest BASE processor speed.
Geekbench is deceiving in that it will reflect the top turbo boost speed, which the imac cannot sustain very long in real world use.

Yes. The Geekbench scores are meaningless here, and not representative of real world use cases. They show potential of what Apple is withholding. My biggest question, is what frequency the i5 finds at steady-state load, and, what Cinebench score does it obtain.

 

[propower]

My biggest question, is what frequency the i5 finds at steady-state load, and, what Cinebench score does it obtain.

This help?
https://forums.macrumors.com/threads/i5-9600k-benchmarks.2175695/#post-27240442
https://forums.macrumors.com/threads/i5-9600k-benchmarks.2175695/#post-27242142

 

[Bohemien]

I haven't seen enough on the i5 to know. While the i9 is no slouch, it is power hungry, and greatly restricted in the iMac. The i5 is much less power hungry, and will likely not be restrained as much. Curious to know how much...haven't seen this yet in the wild.

A test was posted here, with the i5 performing Cinebench at 4.1-4.2 GHz while drawing 80W. Fans were running at 1850RPM max. during 10 runs of Cinebench.

If it were my money, I'd start with the Vega, then consider the i9. The Vega architecture is much better and more efficient than the older Polaris. Though, these questions are privy to your specific workflow.

That workflow being gaming or video editing? Is there any advantage of getting the Vega when the typical use is photo editing, office work and music production?

The Geekbench scores are meaningless here, and not representative of real world use cases. They show potential of what Apple is withholding. My biggest question, is what frequency the i5 finds at steady-state load, and, what Cinebench score does it obtain.

In the post mentioned above, the Cinebench score achieved was 2595.

So far, it seems to boil down to: the i5 will run at a little over 4GHz with 6 cores, from the benchmarks I saw in different tests and here I'd say overall it should perform a little bit better than the 2015 top-spec model (i7-7700K).

The i9 seems to clock in at 3.9GHz, but with 8 cores and 16 threads, so in theory it could be approx. 50% faster than the i5 at similar tasks. I thought I had seen a Cinebench score somewhere right below 4000 that supported that theory but couldn't find the source anymore. (EDIT: it was 4067 - look here.)

This is for software that utilizes all cores, however, so I guess the i9 over the i5-9600K makes sense for "productive" users, not so much for gamers. So I'd venture to sum up:

(1) The i9 with 580X graphics is a monster for people who want to use it for stuff like number crunching, photo editing, running VMs etc.

(2) The i5 with Vega graphics might be the way to go for gamers who don't want to spend ALL that money.

(3) The i9 with Vega will be the machine to get for daily 4K video editing and people who want the maximum possible for games. Bear in mind, however, that you will hear the fans during gaming (referenced here), but maybe not as annoying as in the 2017 i7-7700K model.

Correct? Or did I get anything wrong?

 

[Bboble]

This help?
https://forums.macrumors.com/threads/i5-9600k-benchmarks.2175695/#post-27240442
https://forums.macrumors.com/threads/i5-9600k-benchmarks.2175695/#post-27242142

Clearly I fail at searching! As Cinebench R20 is new, it's hard to find a large source of other 9600k to compare with, but, I'd say 2595 @~4.2GHz is very respectable and healthy, especially as someone got 2906 on a 5GHz 9600k overclock.

That workflow being gaming or video editing? Is there any advantage of getting the Vega when the typical use is photo editing, office work and music production?

In my case, it'd be CPU bound rendering, but, the i9 will render better than i5, hands down. I would never buy an iMac for gaming or rendering, though. The justification to start with Vega graphics in the iMac is multifold. I've read that some music production has some latency issues with different GPUs, but you'd have to look into your specific case.

First, driving the amount of pixels of the display requires a lot of power, and I see it as more of a future-proofing purchase. If the CPU is socketed, as has been in the past, you can always upgrade down the road.

Second, the GPU heat saturates the heat spreader, so, I'd prefer to feed it less heat per performance output. Though, you could argue the i9 is more performance per watt, too.

Third, the going trend has been to offload CPU work on the GPU, so, again more future-proofing here.

Lastly, I don't see the i5 as gimped as the i9, and, for that, I hate paying for something I'm not entirely getting. Though, while $400 for the CPU isn't bad, $450 for the GPU upgrade is a sad Apple joke.

I'd venture to sum up:

(1) The i9 with 580X graphics is a monster for people who want to use it for stuff like number crunching, photo editing, running VMs etc.

(2) The i5 with Vega graphics might be the way to go for gamers who don't want to spend ALL that money.

(3) The i9 with Vega will be the machine to get for daily 4K video editing and people who want the maximum possible for games. Bear in mind, however, that you will hear the fans during gaming (referenced here), but maybe not as annoying as in the 2017 i7-7700K model.

Correct? Or did I get anything wrong?

I largely agree, though, true gamers would never buy a mac to game. In total, if your workflow is not optimized to utilize multicores, or multithreads, and / or it benefits from higher frequency clocks, get the i5. If you need all the horsepower you can get and are considering the i9 with Vega, I'd strongly consider the iMac Pro, especially as the base can often be had at $1000k off.

 

[Ethosik]

Restricting a processor's power input—by the very definition—is thermal throttling. Furthermore, Intel rates the 9900k as having an all-core boost of 4.7GHz sustained. The 5 GHz rating is for only having 2 cores active. My custom built PC with 9900k sustains 4.7GHz on all cores, at ~75C with the Noctua NH-U14S air cooler, albeit at about 135 watts while running Cinebench.

Interestingly, I've seen that the iMac Pro can dissipate ~135 watts at 85C. Thence, Apple themselves have proven that they could more suitably cool the processor they're advertising. Turbo frequencies are Intel designed to be sustained under load, and, the present i9 iMac has shown it can only sustain a few hundred MHz above base clock of 3.6 GHz, not the 1.1 GHz Intel advertised. Again, if Apple cannot cool Intel's i9 chip to work as designed and marketed, then they need not advertise it as the full Intel chip.

Restricting a processor’s power input? Intel’s specs state 95 W. And the same information that Apple provides - 3.6 GHz.

https://www.intel.com/content/www/us/en/products/processors/core/i9-processors/i9-9900k.html

So it comes already thermal throttled? No people just need to stop using that term for cases like this one. We have not seen any evidence that it goes below 3.6 GHz when hot which is what thermal throttling is. Apparently is is very difficult to even get the fans going!