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iMac Pro -- reasonable expectation for performance?


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Hi guys,

I'm supporting a photographer/architect client complaining of intermittently lagging computer performance. He's got a 2017 iMac Pro with the following specs:

• 3 GHz Intel Xeon W processor

• 64 GB RAM

• 1TB flash storage

• Radeon Pro Vega 64 graphics card

The issues seem to arise when opening very large (1.5GB+) raw files in Lightroom, then trying to edit them in Photoshop. He was also saying opening images and especially larger PDFs in Preview was problematic for him. Lastly he claims that YouTube videos will intermittently play very fast, causing a 3-5 minute video to speed up and complete in 15-30 seconds, though I was unable to replicate this. I recommended a partner tech of mine run Onyx, which he had a few weeks ago and it seemed to help temporarily, however the issues have since returned so I came in myself today. When I first arrived I found Lightroom unresponsive. He had about 20 windows open in various apps, including Lightroom, Safari, Mail, Preview, PDF Expert Pro, and Photoshop. After rebooting though the machine seems much more responsive. Still, when I open one of the larger files in Lightroom, then Edit In > Photoshop it takes about 30 seconds to open in PS.

I guess what I'm wondering if this is expected behavior for a machine of this caliber? Seems like a super high-end machine like this should be able to power through most anything you throw at it? But then again, maybe intensive use and lots of caches can bring down even the mightiest machine.  I asked him about how often he reboots, and his reply was "whenever things slow down", so it seems like it might not be that often. I suggested the once per week reboot methodology of clearing caches. I also created a test user for him, though due to the intermittent nature of the issues I'm not sure how much benefit it will be. 

I've heard of some graphics issues with the iMac Pro machines and wonder if there's a way to test for that. This would also lend itself to the weird accelerated YouTube thing.

I recall MacOS used to have a diagnostic if you rebooted holding D, though I haven't been able to get that to work. 




How much freespace does the hard drive have. Can he set his apps to point to another hard drive for scratch data?

Re the new temporary user acocunt – that's a great idea! Let him play around in that account. While he is trying things out, ask him to keep a note pad around (pen and paper) so that he can jot down at what time issues occur at and which app he considers as the cause.

Try starting up the machine with the shift key followed by a restart. Run Disk Utility.

Run software update in case.

If he has external devices connected to the Mac, disengage those long enough to surpass the time that issues would typically start. This will help isolate if there are any 3rd party devices causing the issue or potentially faulty cables or ports.

Is the RAM certified to work in his Mac? Faulty RAM could be a potential issue.

Are there any rotational drives attached. Are any of those reporting SMART related issues.

You'll need to isolate the issue as much as possible to begin understanding if the issue reported is sofware or hardware related. Disconnecting hardware first is a great isolation step. Don't take it for granted that those devices, cables or ports on the Mac are good, assume they are not.

The next isolation step is to determine, should issues persist after disconnecting and external/internal 3rd party hardware, is software isolation. A new user account is absolutely brilliant. Below the user account is the OS. If things work in a new user account without issue you know it's something in his user account. Before you go looking there though, consider adding back 3rd party hardware in the test user account to ensure those devices play well in the test account. If all is still well then the suspicions rise on his main user account.

If issue persist in a new user account with 3rd party hardware disconnected then the OS has something that makes the experience an unhappy one. At that point I would back up and use recovery to reinstall.

Please review this article to help save yourself and your client time. It will repeat some of what I said here but I am sure the article has had more thought put into it., Isolating issues in Mac OS X

As always, ensure the customer has a back up (careful though, when restoring software you might bring back the issue so keep notes for yourself on what you are doing and why).

Have a plan, write it down, explain it to your client. It's important that the relationship you have with your client centers around trust and understanding the general scope of what and why something is being done. You don't have to over explain but simply say that there is hardware, software and any third party hardware and software that he might have added since purchase.

I could or should also mention that you can ask him when he first saw the issue, how long ago? Was it related to anything he might have installed or added to the computer configuration, be it hardware or software.

It wouldn't hurt to run a virus scan. Malware bytes is free for the basic kit.

Let us know how it goes and if there is any other detail you want to offer please do.


2 Answers

If he is trying to open a 1.5 GB file from an external drive yeah, that's the issue, ask him to try it with a file on the Flash drive and he should see a big difference. It won't be 1 sec though, this is a big file.

When you say "Flash" I assume you mean SSD, as not all SD or USB based flash drives are fast.

Yes, the internal SSD drive, sorry.


1.5 GB RAW??? What kind of camera does he have?? Is he working locally, from the Flashdrive or from an external drive? Opening a raw file from lightroom in PS when it's stored on a network drive doesn't work for me (on a Synology). If it's on an external drive, maybe that's the issue?

The originals are on a 4TB Lacie rotational connected through USB. Is this the issue?

It certainly could be the issue, especially if it is an older Lacie rotational drive with a USB 2.0 interface. USB 2.0 speeds are often in the range of 20-30 MB/sec, which means that it could take up to a full minute to open a 1.5 GB file. Even if it is a USB 3.0 external hard drive it will still top out a little above 100 MB/sec, which would mean that it would take 15 seconds to open that 1.5 GB file. See:

Thanks everyone! I think this solved it. You all rock. 🙂