2019 iMac i3 3.6GHZ processor stuck at 0.8 GHZ

[macguru9999]

I have a 2019 iMac i3 3.6GHZ running very slow. NOT drive related, its booted off an SSD. The CPU is stuck at 0.8 GHZ, instead of 3.6 GHZ. I tried resetting everything, p-ram, PMU no dice. The sensors show its running cool, as you would expect since its at 1/4 speed ! If you bypass the PMU then it gets full fans and 3.6ghz. any ideas ? I have ordered an i5 8500 to swap in and 2600 ddr4 ram but if its the mobo then maybe the same thing will happen again ?

 

[zarmanto]

I'm assuming that 800MHz is the base clock speed for that CPU; does that sound right? And are you saying that you've also already tried running something processor intensive on it, such as benchmarking software or a graphics intensive video game or something?

I mean, I've never actually used any of the i3 Macs, as I generally equate the i3 to the older, frustratingly slow Celeron (or "celery") processors... but maybe the i3 just needs a little more upward pressure to prompt it to get off of its butt and start trotting.

 

[robotica]

CPU fan failed maybe? Sounds like its in some kind of limp mode

 

[macguru9999]

The fans work, benchmarks are about 10percent the correct values, its in a limp mode for sure

i have a compatible i5 8500 coming so if that does not set it to rights with some fresh thermal paste then its the mobo.

 

[Fishrrman]

If you boot to the internal drive, does it still run that slow...?

 

[macguru9999]

If you boot to the internal drive, does it still run that slow...?

yes, its independent of the boot drive

 

[macguru9999]

OK, so I ordered an i5 8500 CPU, and I already had some 2600 DDR4 ram, and I pulled the thing apart and ... it works ! Intel powergadget shows the max speed as 4.1ghz instead of 0.8ghz and the fans and everything feel normal. I can report that the old thermal paste was dry and thin but i dont know whether the issue was that, or the 3.6ghz i3 cpu had simply failed. I won't be wasting any time finding out though... I am more than happy with the result, and I have an almost free 2019 imac. (the cpu cost $145 aud)

 

[DavidSchaub]

I have a 2019 iMac i3 3.6GHZ running very slow. NOT drive related, its booted off an SSD. The CPU is stuck at 0.8 GHZ, instead of 3.6 GHZ. I tried resetting everything, p-ram, PMU no dice. The sensors show its running cool, as you would expect since its at 1/4 speed ! If you bypass the PMU then it gets full fans and 3.6ghz. any ideas ? I have ordered an i5 8500 to swap in and 2600 ddr4 ram but if its the mobo then maybe the same thing will happen again ?

Mine does this all the time too. Did you find anything out?

 

[macguru9999]

Mine does this all the time too. Did you find anything out?
View attachment 2106384

YES, I think this is an issue with some imacs .... All I can say is, since fitting the new cpu, a compatible i5 6core model, the imac 2019 has worked perfectly ... i have used it alot and currently have monterey installed on the ssd. All i can assume is that some processors fail, and go into a limp mode. Its quite alot of work to replace it, but if you are able to do the work yourself its obviously worthwhile. (i think the 0.8ghz is a clear indicator yours has the same issue)

 

[ddorsett]

I have a 2019 iMac i3 3.6GHZ running very slow. NOT drive related, its booted off an SSD. The CPU is stuck at 0.8 GHZ, instead of 3.6 GHZ. I tried resetting everything, p-ram, PMU no dice. The sensors show its running cool, as you would expect since its at 1/4 speed ! If you bypass the PMU then it gets full fans and 3.6ghz. any ideas ? I have ordered an i5 8500 to swap in and 2600 ddr4 ram but if its the mobo then maybe the same thing will happen again ?

Hi, I also have a 2019 iMac 3.6, HD write/read speeds in Black Magic tests of about 85 MBS/s (pic attached), and am reading about booting from an SSD radically improvoing things. Seeing your postl I wanted to ask do you rec this? Sounds like potential issues may arise. Thx for any advice, I used to write C++ software but being a self taught coder, my hardware knowledge is uber limited.

 

[macguru9999]

Hi, I also have a 2019 iMac 3.6, HD write/read speeds in Black Magic tests of about 85 MBS/s (pic attached), and am reading about booting from an SSD radically improvoing things. Seeing your postl I wanted to ask do you rec this? Sounds like potential issues may arise. Thx for any advice, I used to write C++ software but being a self taught coder, my hardware knowledge is uber limited.

just open it up, or get someone else to , and fit a 1tb crucial mx ssd, clone back the data or reinstall. its extremely unlikely you will need to do anything else, but jus tape back the screen until your sure. you should get 400+ mb/s from the ssd

 

[Gudi]

Hi, I also have a 2019 iMac 3.6, HD write/read speeds in Black Magic tests of about 85 MBS/s (pic attached), and am reading about booting from an SSD radically improvoing things. Seeing your postl I wanted to ask do you rec this? Sounds like potential issues may arise. Thx for any advice, I used to write C++ software but being a self taught coder, my hardware knowledge is uber limited.

iMac Intel 21.5" Retina 4K Display 2019 Hard Drive Replacement

It's not an easy upgrade, but certainly worth it. A SATA-3 SSD can increase your read/write speeds six-fold to well over 500 MB/s. Those bastards really did sell the cheapest 2019 21" iMac with an HDD only. 😩

 

[ddorsett]

just open it up, or get someone else to , and fit a 1tb crucial mx ssd, clone back the data or reinstall. its extremely unlikely you will need to do anything else, but jus tape back the screen until your sure. you should get 400+ mb/s from the ssd

As I see the screen removal being a bit hairy, (and I know I wouldnt get the same speed as an internal SSD), what do you think about my buying this drive ($80 on sale) and running it externally as a boot drive? Guess on the read/write speeds? Looks like my iMac is USB 3.1

Crucial - X8 1TB External USB-C 3.2 Gen 2/USB-A Portable SSD​

 

[Gudi]

As I see the screen removal being a bit hairy, (and I know I wouldnt get the same speed as an internal SSD), what do you think about my buying this drive ($80 on sale) and running it externally as a boot drive? Guess on the read/write speeds? Looks like my iMac is USB 3.1

Crucial - X8 1TB External USB-C 3.2 Gen 2/USB-A Portable SSD​

Use an external SSD as your startup disk with your iMac or Mac mini

It's doable, but I don't know if I should recommend it? Maybe as a first try to experience the difference an SSD makes. It's a safe way and you don't lose any money if the performance is underwhelming.

EDIT: Your iMac does support USB 3.1 Gen 2 (up to 10Gb/s)

 

[macguru9999]

As I see the screen removal being a bit hairy, (and I know I wouldnt get the same speed as an internal SSD), what do you think about my buying this drive ($80 on sale) and running it externally as a boot drive? Guess on the read/write speeds? Looks like my iMac is USB 3.1

Crucial - X8 1TB External USB-C 3.2 Gen 2/USB-A Portable SSD​

Its fast, I used to say it was a good idea, but I have been unable to clean install or update direct to an external drive since monterey. cloning did not work properly either. but big sur it works great. so no, i cannot recommend it anymore. just find someone to do the job.

 

[ddorsett]

Its fast, I used to say it was a good idea, but I have been unable to clean install or update direct to an external drive since monterey. cloning did not work properly either. but big sur it works great. so no, i cannot recommend it anymore. just find someone to do the job.

Shoot I read this after ordering the drive! Suggestions then on how I maximize my chances? As far as transferring data to the new external drive:Time Machine is a bit different than cloning? Havent done either. And is Monterey doable for the external SSD or you are saying it's not? I currently run BigSur and dont seem to have issues with it. Any recs would be very much appreciated, I am only in for $70 and am willing to give it a go. Even a band aid that gets me cpl years would be GREAT if speed increased a good bit. Also dont know much about potentially factoring out having the drive in charge of the OS but using other software already resident on my HDD or if, say, Internet use in general becomes more iffy...? (Note: I truly can't afford having my current system/HDD be rendered unusable or capriciously unstable as a side effect of these experiments if this doesn't pan out and I decide to revert/back out though. I am on Facetime, Skype, Zoom for work a lot...). Sorry for all the Q's here, but per yuor reply I am wondering if I'm going to overshoot the runway here with this gambit....
Thanks very much for your thoughts, highly appreciated.

 

[macguru9999]

as i said, i could clone big sur to the external no probs but not anything higher. others may vary but i tried lots of ways and its not happy running from an external, try it but you may end up stuck on big sur which is not a bad thing. speed will be great if your external is an ssd.

 

[ddorsett]

Will do, wasn't sure if your verbiage "since Monterey" included Monterey. Big Sur it is. R.E. making a clone, (a new task to me), folks rec carbon copy cloner, do you concur?

 

[macguru9999]

Will do, wasn't sure if your verbiage "since Monterey" included Monterey. Big Sur it is. R.E. making a clone, (a new task to me), folks rec carbon copy cloner, do you concur?

ya "since monterey inclusive" and I use CC Cloner 5.x , tho i am pretty sure ccc6 is fine too.

 

[ddorsett]

ya "since monterey inclusive" and I use CC Cloner 5.x , tho i am pretty sure ccc6 is fine too.

Thanks very much again for the help, things have so far gone pretty well with the new external $80 Crucial X8 SSD as boot drive. My blackmagicdesign read/write tests are 10X what they were, pic attached, old tests were mid 80's. Performance, boot time, even internet speed tests consistently way up (didnt realize the drive was needed?). The process only gave me the option to install Ventura (instead of the Monterey I was going to opt for), and it seemed chancy but so far so good, the X8 is now boot drive running Ventura 13.0.1. I did use the option of copying data over from Hd to SSD, (all but sys info). Maybe need to clean stuff up now tho, as I have 2 copies of tons of applications, docs, etc., one on each drive. Though most applications running fine from X8 I might need to tweak or do a few reinstalls. And some complete file pathnames for previously existing files might refer to the old HD, which could give me a weird hybrid situation, if that makes sense (application running on X8 but using a file resident on the HDD....problematic? Guess I'll sort that out as I go.

Outstanding questions (I hope they make sense!):
1. In your opinion, should I be running applications and using/accessing files as much as possible from the X8 alone? If so, is it better to delete the orig copies on the HDD or leave them untouched in case of, say, either needing to boot from that drive for some heretofore unknown reason or - just finding it easier to use them where they exist, on the HDD? (Hybrid scenario mentioned above).
2. Though you can see both drives in Disk Utility(pic attached), I can only see the X8 on my desktop, and if I want to do any of said cleanup I clearly need to get to the orig internal HD.

LMK thoughts, thx much. Best $80 I ever spent on tech gear. (Knock wood!!)

 

[zarmanto]

Outstanding questions (I hope they make sense!):
1. In your opinion, should I be running applications and using/accessing files as much as possible from the X8 alone? If so, is it better to delete the orig copies on the HDD or leave them untouched in case of, say, either needing to boot from that drive for some heretofore unknown reason or - just finding it easier to use them where they exist, on the HDD? (Hybrid scenario mentioned above).
2. Though you can see both drives in Disk Utility(pic attached), I can only see the X8 on my desktop, and if I want to do any of said cleanup I clearly need to get to the orig internal HD.

I can offer one set of opinions for you:

1. You don't necessarily need to unmount the HDD, nor do you need to delete anything from it, but I would certainly recommend copying over to the SSD any of the files that you'd like to continue using actively. You'll gain the faster performance of accessing those files from the SSD, as well as the data security of a more stable medium. (If memory serves, there are some on this forum who disagree with me on this point, but I'm still convinced that SSDs will far outlast HDDs.)

2. Drives other than the current boot volume don't show up on the desktop by default -- but your screenshot seems to suggest that the HDD is at least still mounted. If this is true, you should be able to find it by opening a new Finder window and glancing at the left-hand sidebar; all mounted volumes show up there by default. If you'd like, you can also change the settings for which items are displayed directly on the desktop from the Finder Preferences. Personally, I've found myself veering more towards a clean desktop with no icons at all, (aside from what's on the Dock) but maybe that's just me.

 

[ddorsett]

I can offer one set of opinions for you:

1. You don't necessarily need to unmount the HDD, nor do you need to delete anything from it, but I would certainly recommend copying over to the SSD any of the files that you'd like to continue using actively. You'll gain the faster performance of accessing those files from the SSD, as well as the data security of a more stable medium. (If memory serves, there are some on this forum who disagree with me on this point, but I'm still convinced that SSDs will far outlast HDDs.)

2. Drives other than the current boot volume don't show up on the desktop by default -- but your screenshot seems to suggest that the HDD is at least still mounted. If this is true, you should be able to find it by opening a new Finder window and glancing at the left-hand sidebar; all mounted volumes show up there by default. If you'd like, you can also change the settings for which items are displayed directly on the desktop from the Finder Preferences. Personally, I've found myself veering more towards a clean desktop with no icons at all, (aside from what's on the Dock) but maybe that's just me.

Helpful, thx again.

 

[Fishrrman]

OP wrote:
"should I be running applications and using/accessing files as much as possible from the X8 alone?"

If you are booting/running from the X8, then EVERYTHING should be on the X8 drive, if possible.

Leave the internal drive "in place, but not used".
If you don't want to see it on the desktop, you can drag it to the trash to unmount it.

Or... possibly a better solution... use the free little menu bar utility app named "Semulov" to dismount it (and re-mount when needed).

 

[ddorsett]

OP wrote:
"should I be running applications and using/accessing files as much as possible from the X8 alone?"

If you are booting/running from the X8, then EVERYTHING should be on the X8 drive, if possible.

Leave the internal drive "in place, but not used".
If you don't want to see it on the desktop, you can drag it to the trash to unmount it.

Or... possibly a better solution... use the free little menu bar utility app named "Semulov" to dismount it (and re-mount when needed).

Thanks, will do. The only slight issues I am having (and extremely tolerable, assumedly fixable, and absolutely pale in comparison to the performance benefits) seem to have to do with pathnames of files, maybe(?). I mentioned as part of the Disk Utility/format/new OS process I was prompted to and did copy over a ton of applications, docs - just not sys stuff per se. I am wondering if I am going to need to sometimes do things like opening existing docs (e.g. "recent(s)" while using aplications resident on the X8 and then "save as" somehow making sure to point to the X8 so that the new full pathnames are now relative to the X8. Does the question make sense and is it germane? Since I have 2 copies of so much stuff when I do a search, I'm being careful to know which application I'm launching, or which one I'm making an alias to to put the alias in my dock. I've also re-installed a cpl applications that seemed a tiny bit jenky, no biggie. Housekeeping, but so far the small issues have been pretty easy to solve..