Downgrade to high sierra to get working machines. Good idea?

[Dr Möbius]

Hello, and thank you in advance for all the information that I found in this forum in the past!

During the last years lockdowns I had the great idea of bringing all our 3 machines a little bit more up to date. Those are:
1. iMac (Retina 5K, 27”, late 2015, 4 GHz Intel Core i7, 32 GB RAM, AMD Radeon R9 M395X 4 GB, 3 TB fusion drive)
2. MacBook Pro (15” , mid 2012, 2,3 GHz Intel Core i7, 16 GB RAM, Intel HD Graphics 4000 + NVIDIA GeForce GT 650M, Samsung SSD 850 PRO 256GB + 2 TB HDD)
3. MacBook Pro (15” , mid 2012, 2,3 GHz Intel Core i7, 16 GB RAM, Intel HD Graphics 4000 + NVIDIA GeForce GT 650M, 256 GB Apple SSD)
All computers are used for normal photo and video editing and 3d rendering, no heavy lifting, just normal stuff. They were working really fast and without any problem when I still had mavericks running on the macbook pro and high sierra on the imac. I mean it was really really fast, I had no problems at all. The only reason for the update was, that of course some programs do no longer run on an 8 year old OS. But after I updated all three of them to mojave, I'm experiencing a wide range of problems. I don't want to describe all the problems here. In general all the macs are just slow and programs sometimes crash, which they never ever did before. I installed newer versions of adobe software and all other programs, so that they fit to mojave. But for example editing a 1 GB PSD file was running smoothly before is now a real pain. Video rendering is also a lot slower. Not to speak of 3d rendering which is no more possible at all. So I'm really disappointed now and hope a downgrade to high sierra would help. Especially the iMac should be powerful enough to handle mojave, but to me it seems that the OS is just burning ressources...
I don't need the newest versions of adobe software, I don't need mobile apps on my computer and I don't need night shift and other fancy stuff. All I need is working machines that can finish the jobs as they did before the update. And I need a file transfer between the machines, which is the only thing that improved after the update, airdrop. The reason why I stick to those old machines is because I also have two 27" thunderbolt screens and a lot of peripheric devices and I certainly don't want to carry around all those usb hubs and stuff.
There are many related topics in this forum already. But I have some specific questions I hope someone more experienced has an answer to:
1. should I use HFS or APFS ? Which works better with a fusion drive?
2. Under high sierra, which versions of adobe software would you recommend to run fastest on those machines?
3. Can I update the iMac to 64 GB RAM under high sierra with the fusion drive?
4. any tips and tricks to make the job a success?

THX

 

[Juicy Box]

1. should I use HFS or APFS ? Which works better with a fusion drive?

HDDs and Fusion Drives do much better with HFS than APFS, but not so much of a difference on High Sierra according to many things I have read. With Mojave and especially Catalina, APFS is (relatively) horrible on HDDs.

3. Can I update the iMac to 64 GB RAM under high sierra with the fusion drive?

I assume you are referring to your iMac?

If you get the correct RAM, I don't see why it would not work. Officially, Apple says 32GB, but actual max RAM and Apple's official number often do not match.

4. any tips and tricks to make the job a success?

A few things....

You don't have to have just one or the other when it comes to OS versions. You can dual boot, have a Mojave partition and a High Sierra partition.

For example, my Mac Pro has four different bootable partitions that I pick and choose when I need a particular OS.


Another thing, consider using a SSD, especially if you want to use the newer OS versions. For your iMac, you have lots of options to do external SSDs. The newer OS versions would probably run much better.

You could also keep the Fusion Drive for the older OS versions, and use a straight SSD for the new OS versions.

The Late 2015 iMac has a lot of options:
You can just use USB.
You can use TB1 or TB2 SATA SSD or NVMe.
You could use a TB3 NVMe.
You could swap the internal HDD for an internal SSD.
You could spit your Fusion Drive, and create your own Fusion Drive with your fast internal SSD and a cheap external SATA SSD.

That is just a few options, as there are many more options and combinations.

 

[Dr Möbius]

THX a lot for the detailed answer!

HDDs and Fusion Drives do much better with HFS than APFS, but not so much of a difference on High Sierra according to many things I have read. With Mojave and especially Catalina, APFS is (relatively) horrible on HDDs.

ok, let's try it!

I assume you are referring to your iMac?

If you get the correct RAM, I don't see why it would not work. Officially, Apple says 32GB, but actual max RAM and Apple's official number often do not match.

it should work, but someone said, that it is not optimal with a 128 GB ssd in a fusiondrive...anyway I want to get rid of the fusiondrive

The Late 2015 iMac has a lot of options:
You can just use USB.
You can use TB1 or TB2 SATA SSD or NVMe.
You could use a TB3 NVMe.
You could swap the internal HDD for an internal SSD.
You could spit your Fusion Drive, and create your own Fusion Drive with your fast internal SSD and a cheap external SATA SSD.

Thank you!
before I slice open the iMac I thought it would be good, to first test it with an external ssd and the OS. From what I understand this would be best via TB2, since there is no TB3 USB-C in this iMac. Or maybe I use the slower USB connection with a cheap SATA connector. Not sure what difference that makes...
If the test is positve I'm planning to clone the OS to an internal SSD and exchange the fusiondrive.
I'll post back on this...

 

[Juicy Box]

If you get the correct RAM, I don't see why it would not work. Officially, Apple says 32GB, but actual max RAM and Apple's official number often do not match.

it should work, but someone said, that it is not optimal with a 128 GB ssd in a fusiondrive...anyway I want to get rid of the fusiondrive

I am definitely not saying that that isn't true, but I haven't heard this, and have no idea why the Fusion Drive would impact the maximum amount of RAM that can go in the iMac.

before I slice open the iMac I thought it would be good, to first test it with an external ssd and the OS.

This is a great idea, one that I highly recommend doing prior to swapping out the internal drives.

Get everything up and running externally first, then go internal if you choose to.

From what I understand this would be best via TB2, since there is no TB3 USB-C in this iMac.

You can use TB3 drives with TB1 and TB2 ports on Macs. My late 2012 iMac is currently booting from a TB3 NVMe. To do this, you need the Apple bidirectional adapter.

But.... The downside is that there is no power over the bus when using the bidirectional adapter. So, if the TB3 device you are wanting to use does not have its own power source (like an AC adapter), then you need something in between your Mac and the TB3 device to power it, such as a powered TB3 dock.

Since just about all TB3 NVMe drives are bus powered, this means you will most likely need a TB3 dock, in additional to Apple's bidirectional adapter, and the TB3 NVMe drive.

Between the TB3 NVMe drive, TB3 dock, bidirectional adapter, and TB2 cable, and maybe a TB3 cable for the TB3 NVMe drive, this is quite an investment, and usually not worth it to most people as the alternatives could be almost as cheap, less equipment, and much cheaper.

Although, if you plan on getting a newer Mac in the next few years, the investment in the TB3 stuff might not be that big of a deal as you can use it with your new future Mac.

Or maybe I use the slower USB connection with a cheap SATA connector.

This is the cheapest option, and one I recommend if money is an issue, or if it is meant to be temporary until you install the drive internally.

I love this SATA/USB3 cable here:

SABRENT USB 3.0 to SSD / 2.5 Inch SATA I/II/III Hard Drive Adapter (EC-SSHD)

Product Description:Take advantage of the lightening speed of USB 3.0 to quickly transfer files up to 5 Gbps! Connect any 2.5'' Serial ATA (SATA) / SSD or SATA II Hard Drive to your computer through an available USB 3.0 port on your desktop or laptop. Reverse compatible with USB 2.0 and 1.1, this...

www.amazon.com

It is nice because the cable length is longer than much of the other cables I have seen, and it is really cheap. The price has gone up a little, as I got a bunch of them when they were only $7. But, now they are $10.

Still, they are very good cables, and very helpful to quickly connect 2.5" drives.

Not sure what difference that makes...

A big difference is cost, speed, and TRIM support.

USB will be the cheapest option and easy to find, but also a slower option, and no TRIM support. With USB3.2 Gen1 (5Gbps), which your iMac has, you would probably see around 350-450Mbps sequential read speeds using a SATAIII SSD. This is a great option for quickly and/or temporarily connecting a SATA drive for setup or troubleshooting. But, also okay for long-term as well as long as the Lack of TRIM doesn't become an issue.

TB1 (10Gbps) will have TRIM support and be slightly faster with SATAIII, but more expensive, and much harder to find. I have found used ones on eBay with HDDs in them. I pulled the HDDs, and replaced them with SSD.

TB2 (20Gbps) with have the benefits of TB1, but will be almost twice as fast and are easier to find. You will probably see no improvement with SATA drives, but you could with AHCI or NVMe drives, giving you about 800 - 1500Mbps speeds.

TB3 (40Gbps) with have all the benefits of both TB1 and TB2, but much easier faster to find. The downside would be that it is more expensive and requires additional equipment to run on your iMac due to no power via the bus. You can see speeds up to 3000Mbps with TB3.


But, it all comes down to you, your budget, and what you need, and what you have planned.

If you want to use something external, and might consider doing something internal one day, I suggest just getting a 2.5" SATA SSD and use it with a USB3 enclosure or adapter cable. You can set it up, and use the SATA SSD externally for a while, and if you ever feel like replacing the internal HDD, you already have a SSD ready to use.

 

[Dr Möbius]

I love this SATA/USB3 cable here:

SABRENT USB 3.0 to SSD / 2.5 Inch SATA I/II/III Hard Drive Adapter (EC-SSHD)

Product Description:Take advantage of the lightening speed of USB 3.0 to quickly transfer files up to 5 Gbps! Connect any 2.5'' Serial ATA (SATA) / SSD or SATA II Hard Drive to your computer through an available USB 3.0 port on your desktop or laptop. Reverse compatible with USB 2.0 and 1.1, this...

www.amazon.com

Thanks, the cable came yesterday and it works quite well.

Now, I will use a Samsung 860 pro 512 GB SSD, connect it with the cable and install high sierra on it. I never did a downgrade before and realized high sierra cannot simply be installed on the external drive from a mc running Mojave. I still have an even older macbook pro from 2008 and will give it a try to install from there as operating station...
So I will report back here how it went.

 

[Dr Möbius]

Alright. I created a bootable USB stick using this guide:

How to create a bootable USB masOS installer

Make a macOS installer with createinstallmedia and install Monterey or another macOS on multiple Macs, do a clean install, or access a faulty Mac.

www.macworld.co.uk

Then I installed High Sierra on the SSD connected via USB. Everything went without any trouble and after finishing the installation. I rebooted (holding alt key) and selected the fresh install on the SSD and went directly into a fresh install of High Sierra. Though connected via USB, without TRIM support it makes no sense for me to really work on that drive. But I will test some programs and then put it into the MBP, since it is really easy to install in those mac books (other than the iMac...)