For people who believe 64GB memory is too much. It's possibly not.

[Andrey84]

My wife's iMac memory usage under: "I've got nothing open!" is below.

I don't know why she said that; clearly, she's got everything open.

I saw several people here concerned about having "wasted" or "idle" memory, when opting for 32 or 64GB with a new Mac. I believe there is no such thing, really, as "wasted" memory, under specialist professional use, with a 64GB config and under.

I want to show that under this real-world scenario, without opening any kind of movie files and working on just 1 project file per large application, Mac OS uses 75GB for application memory plus 18.6 GB for caching, making it

93.6 GB in total.

I'm not suggesting to anyone to get any specific amount of memory. Of course this will work on 32GB. The question is - how much lag will the user experience when switching between applications, and is the user willing to put up with these lags?

The primary meaning of this post is to prompt undecided potential buyers to examine their RAM requirements very carefully.

UPDATE 12.01.2024

I do understand this post is ignorant and I had no idea how memory management works. Please please please, let this post just die, so I don't get daily reminders of how ignorant I am. I've been put in my place and humbled to the fullest. Please don't kick someone who is already down.

Also wanted to say big thanks to the forum members, who engaged in a positive way and gave great evidence-backed answers. You've changed how I view the unified memory requirements.

My key learnings:
- Used Memory is not really important for performance, Memory Pressure is important
- Even with yellow memory pressure there can be no noticeable difference in performance
- You don't need to buy extra unified memory on Apple Silicon Macs to compensate for the lack of dedicated video memory, which Intel Macs have
- Mac OS caches all files the user opens in RAM, if there is lots of RAM available, this is called “Cached Files”
- Mac OS won't ‘fill up’ all available RAM. However, if there is free RAM, Mac OS will use any opportunity it has to optimize performance: it will cache files in memory or allocate memory to applications, if they ask for it

With my wife's Mac Studio purchase several years down the line, we'll very seriously consider going down from 128GB to 64GB, if the 'customer' allows it, and if it means we can get a good deal
For my purchase of 15" MacBook Air, also several years down the line, I can now be guilt-free and get just 16GB and save £200 without any impact on performance, assuming there will be the same options as now

 

[chabig]

Are you trying to make a point? That wasn't clear to me with just a topic and a picture to go on. Everything looks normal in the picture.

 

[Andrey84]

The point is in the subject. I personally didn't know it was possible, without running servers or VMs, to hit 75GB application memory used. It turns out to be quite easy.
I'm posting this as an illustration for people who want to save $300 and buy a Mac with less unified memory than what they might need in the future.

 

[chabig]

Your subject, "For people who believe 64GB memory is too much" just doesn't assert anything so I wan't sure. I think you are trying to make a point that macOS uses memory. Everyone knows that. In fact, it will use as much as it can get for maximum efficiency. All of those apps your wife has running on that 128GB machine will also run fine on machines with less RAM.

 

[Andrey84]

<deleted comment>

 

[Contact_Feanor]

Modern OSes try to fill up memory. the fact she uses 75 GB here is virtually meaningless (speaking as someone who has 96GB on his MBP)

 

[arw]

^^ this.
With zero swap and green memory pressure no one can say if the same machine with only 16 GB would not feel and behave 100% identical in the given scenario.
(Not saying larger Adobe projects don't benefit hugely of more RAM).

That being said, one thing I have never seen mentioned anywhere is the advantage of having great amounts of free RAM for "Cached Files":
When working with files located on spinning HDDs or on network storage (even Gigabit) this is extremely useful if the same file is accessed more than once - because it is available almost instantly if cached in the RAM. This is independent of the application but handled completely autonomous by macOS.

 

[Andrey84]

Modern OSes try to fill up memory. the fact she uses 75 GB here is virtually meaningless (speaking as someone who has 96GB on his MBP)

What exactly do you mean? Also, why do you believe this is happening?

 

[MRxROBOT]

What exactly do you mean? Also, why so you believe this is happening?

macOS uses free RAM for caching. It will use up as much as it can.

 

[Andrey84]

^^ this.
With zero swap and green memory pressure no one can say if the same machine with only 16 GB would not feel and behave 100% identical in the given scenario.
(Not saying larger Adobe projects don't benefit hugely of more RAM).

That being said, one thing I have never seen mentioned anywhere is the advantage of having great amounts of free RAM for "Cached Files":
When working with files located on spinning HDDs or on network storage (even Gigabit) this is extremely useful if the same file is accessed more than once - because it is available almost instantly if cached in the RAM. This is independent of the application but handled completely autonomous by macOS.

Thanks. Are you able to substantiate what you’re saying though?
Hope you can understand, it’s very hard to believe that with 75GB memory used the machine will behave the same with just 16GM of RAM.
Also, what about 8GB? You must have some kind of calculation on how you’ve arrived at 16GB. Hope your calculation isn’t “it’s enough for most people”.

 

[Andrey84]

macOS uses free RAM for caching. It will use up as much as it can.

How is RAM caching not a legitimate use of RAM? If I’m not using an application right now, I would like for it to be instantly available with all its data ready for me to use when I switch back to it.

 

[okkibs]

it’s very hard to believe that with 75GB memory used the machine will behave the same with just 16GM of RAM.

No worries, it's not just hard to believe it's impossible. The Adobe apps as well as Rhino3D have a minimum total system memory recommendation of 8GiB each. All of them running at the same time wouldn't work. To some degree apps can minimize their memory usage and whatever spills over into swap won't immediately break anything. With 66GB of usage just for the apps on their own you could get by with 64GiB and let the app's optimizations, the MacOS compression as well as the swap space to their thing and the Mac will keep on running with some performance hickups. Obviously it's not particularly great to buy a new Mac that is then brought to its limits right away.

So even though this would work, if you're running the creative cloud with apps using memory in the double digits and you're sitting at 75GB used and then you go out to buy a new computer where you can't add RAM later... you only got yourself to blame if you don't leave some head room or even buy a 16GiB model. When that thing grinds to a halt immediately preaching "unused ram is wasted ram" won't help.

It's a good thing that the 128GiB aren't fully used. It guarantees full performance and allows for apps to have increased requirements with updates over the years. I'd rather have some memory "go to waste" rather than running out.

How is RAM caching not a legitimate use of RAM? If I’m not using an application right now, I would like for it to be instantly available with all its data ready for me to use when I switch back to it.

The caching here is actually for regular files you store on the harddrive, or rather files that currently open apps are accessing. Open applications themselves are always kept in memory, which makes up the 66GB of "app memory" in the screenshot. The file caching is the "cached files" entry.

 

[Contact_Feanor]

Thanks. Are you able to substantiate what you’re saying though?
Hope you can understand, it’s very hard to believe that with 75GB memory used the machine will behave the same with just 16GM of RAM.
Also, what about 8GB? You must have some kind of calculation on how you’ve arrived at 16GB. Hope your calculation isn’t “it’s enough for most people”.

How about this: logged out and back in on 2 Macs, opened the exact same apps, one has more RAM than the other, look what happens; there's some background processes that differ between the two, but in general the same apps use different amounts of RAM on both: SC2 and Messages use 4x more RAM, Finder, Mail and Safari 2x the RAM, etc. Everything together, the one with more RAM has 3x as much RAM in use than the one with less RAM.

 

[Andrey84]

No worries, it's not just hard to believe it's impossible. The Adobe apps as well as Rhino3D have a minimum total system memory recommendation of 8GiB each. All of them running at the same time wouldn't work. To some degree apps can minimize their memory usage and whatever spills over into swap won't immediately break anything. With 66GB of usage just for the apps on their own you could get by with 64GiB and let the app's optimizations, the MacOS compression as well as the swap space to their thing and the Mac will keep on running with some performance hickups. Obviously it's not particularly great to buy a new Mac that is then brought to its limits right away.

So even though this would work, if you're running the creative cloud with apps using memory in the double digits and you're sitting at 75GB used and then you go out to buy a new computer where you can't add RAM later... you only got yourself to blame if you don't leave some head room or even buy a 16GiB model. When that thing grinds to a halt immediately preaching "unused ram is wasted ram" won't help.

It's a good thing that the 128GiB aren't fully used. It guarantees full performance and allows for apps to have increased requirements with updates over the years. I'd rather have some memory "go to waste" rather than running out.


The caching here is actually for regular files you store on the harddrive, or rather files that currently open apps are accessing. Open applications themselves are always kept in memory, which makes up the 66GB of "app memory" in the screenshot. The file caching is the "cached files" entry.

Thanks so much for your comment and explanation of caching as well.
I’m a big proponent of getting as much memory as it’s reasonably possible.

I’m trying to dispel the myth going on on these forums that 16GB of unified memory is enough for everything. Maybe people haven’t really experienced serious swapping? Have they bought into the idea that unified memory is somehow special? It’s been proven it’s not. Swapping on a super-fast SSD is still swapping.

Agree that 64GB could’ve probably worked in my wife’s scenario, however she now has 16GB dedicated for VRAM on top of 128GB RAM, which Mac Studio won’t have. So it should be 96GB or above when she goes for the Studio.

 

[Andrey84]

How about this: logged out and back in on 2 Macs, opened the exact same apps, one has more RAM than the other, look what happens; there's some background processes that differ between the two, but in general the same apps use different amounts of RAM on both: SC2 and Messages use 4x more RAM, Finder, Mail and Safari 2x the RAM, etc. Everything together, the one with more RAM has 3x as much RAM in use than the one with less RAM.

Thanks for this test, but it doesn’t prove anything to me. Yes I know that if RAM is larger, usage is always more, but where exactly does the swapping start?

Well actually, case in point, your 64GB machine is swapping!

Also in your case I’m preaching to the converted, you’ve already got 64GB and 96GB on your machines - wise choice! With all due respect, you’re not my target audience

 

[Contact_Feanor]

Thanks for this test, but it doesn’t prove anything to me. Yes I know that if RAM is larger, usage is always more, but where exactly does the swapping start?

Also in your case I’m preaching to the converted, you’ve already got 64GB and 96GB on your machines - wise choice! With all due respect, you’re not my target audience

For my husband I specifically and willingly bought an 8GB RAM MacBook Air because that's more than enough for regular use and some light photoshop and even blender...

 

[Lordart]

Wasn't sure if I should have posted here but just opened another thread asking for advice on whether 64gb on a M2 Studio Max is more than enough for Photoshop/Illustrator as a full time artist... or if the 96gb is worth it ... sounds like my gut feeling of the 38core 96gb Max is the way to go with the Ultra being out of budget range. 🤔
(currently on M2 pro mini 32gb ram)

 

[weezin]

I'm not sure I understand either. The memory pressure graph in the screenshot is incredibly low. That's what you should be using to assert whether you have too little ram. With 128GB of ram and the memory pressure that low, you'd do just fine on quite a bit less ram.

 

[MacProFCP]

Our 2019 Mac Pro came with over 100 GB of ram. Now it has 256 GB. Major and noticeable difference, even in the time it take Microsoft Word to open.

 

[Contact_Feanor]

Our 2019 Mac Pro came with over 100 GB of ram. Now it has 256 GB. Major and noticeable difference, even if the time it take Microsoft Word to open.

That's all to do with the cpu, not the RAM

 

[MacProFCP]

That's all to do with the cpu, not the RAM

Not according to Activity Monitor.

 

[Contact_Feanor]

Not according to Activity Monitor.

So activity Monitor is telling you that word is opening faster because you have more RAM? How exactly is it telling you that?

 

[MacProFCP]

So activity Monitor is telling you that word is opening faster because you have more RAM? How exactly is it telling you that?

Activity Monitor is telling me that I am utilizing over 40 GB while NOT doing heavy work and often over 100 GB or 150 GB while doing heavy work.

Regarding word. Prior to the upgrade, it would take up to 30 second to load. Typically 10 seconds minimum. Now, less than 2 seconds.

 

[MRxROBOT]

How is RAM caching not a legitimate use of RAM?

With that logic, you might as well run your entire OS and all files off a RAM disk. Just to clarify, I don't think 64GB is too much for everyone. I have 96GB, the most I could equip my M2 Max with.

 

[boss.king]

My wife's iMac memory usage under: "I've got nothing open!"

I don't know why she said that; clearly, she's got everything open.

I saw several people here concerned about having "wasted" or "idle" memory, when opting for 32 or 64GB with a new Mac. I believe there is no such thing, really, as "wasted" memory, under specialist professional use, with a 64GB config and under.

[SNIP]

And if you had 1TB of RAM, the computer would likely be using into the hundreds of gigs. I don't think any reasonable person has ever said that 64GB is too much RAM, but rather that less is often enough in many cases. If RAM was free then sure, everyone should load up on as much as they can, but it's not and so blowing money on something you don't need seems kinda dumb and wasteful. That's not to say it's not needed in this case, but just showing a screenshot with more than 64GB in use is proof of nothing.