CPU/RAM demand increase moving from 2 displays to 3?

[wikeeboy]

I currently have an M3 MacbookAir 16gb. I only run 2 screens as it won't run 3 Apple screens (thunderbolt) simultaneously which is what i need.

CPU usage seems pretty low for my average usage, but my 16gb of RAM is constantly running at 14gb+.

The new M4 Pro Mini will now handle 3 Apple screens so i'm going to buy one but am wondering which CPU and RAM to select. On my current Mac Air if i was to hypothetically run an extra screen (3 in total) i'm trying to understand how much extra CPU or RAM this may gobble up. If i'm already using up 16gb RAM consistently, will adding an extra screen require much more or has this little to do with it? The M4 Pro comes with 24gb so quite possibly that extra 6gb will be enough. If not i can go for 48gb but it's a significant cost increase.

I'm assuming an extra screen running won't really tax the CPU/GPU?

Appreciate any advice and opinions.

 

[xraydoc]

I currently have an M3 MacbookAir 16gb. I only run 2 screens as it won't run 3 Apple screens (thunderbolt) simultaneously which is what i need.

CPU usage seems pretty low for my average usage, but my 16gb of RAM is constantly running at 14gb+.

The new M4 Pro Mini will now handle 3 Apple screens so i'm going to buy one but am wondering which CPU and RAM to select. On my current Mac Air if i was to hypothetically run an extra screen (3 in total) i'm trying to understand how much extra CPU or RAM this may gobble up. If i'm already using up 16gb RAM consistently, will adding an extra screen require much more or has this little to do with it? The M4 Pro comes with 24gb so quite possibly that extra 6gb will be enough. If not i can go for 48gb but it's a significant cost increase.

I'm assuming an extra screen running won't really tax the CPU/GPU?

Appreciate any advice and opinions.

I currently use a 14" M3 Max (14/30-core model) as my desktop machine connected to three Studio Displays. I've got 36GB RAM in my machine and it performs very well.

Activity Monitor generally has my memory usage at ~26GB and memory pressure in the green with my usual suite of apps running (Mail, Calendar, Safari, Edge, Discord, iMessage, Word, PowerPoint, plus a few background utilities like Dropbox, ChatGPT, Al Dente Pro, Smooze Pro and a handful of macOS desktop widgets).

Even when I use more memory-intensive apps like Parallels (for a Windows 11 VM allocated 8GB of RAM), Falcon MD and Osirix MD, I've never seen the memory pressure push itself into the red nor have I received "memory low" warnings from macOS. It does occasionally swap to the SSD in those situations, but it's so fast that I'd never know unless I looked at Activity Monitor.

Depending on what you're doing, you could certainly get by on 24GB, but if you're truly looking at three displays, I'm going to guess you're a bit of a power user, which in that case, 24GB might be pushing the lower limit.

The extra displays don't really put any additional burden on the CPU (aside from the apps residing on those displays), but the GPU does work to keep OS animations and such up to speed spread across all those extra pixels. However, I don't expect the M4 Pro's GPU to struggle with that (unless you're attempting to play a game spread across all three simultanously).

 

[streetfunk]

i´d like to know the very same thing as the OP.
But please, as numbers vs. what a 3rd display really will take.

How much load will one screen more add to the RAM ?
In my case 2K resolution.
What´s your, the knowledgable folks, estimation vs. a 2K screen, vs. a 4K screen vs. undemanding contents. Audio work in my case. While I would guess different usecases might change that RAM load. So much likely a very fluid thing vs. numbers ? and in that sense not easy to be answered ?


I consider statements like "this and that amount of RAM will be fine for you" not as an asnwer.
it is not answering the real query here.
"We", the unknowledgable, would like to get an overwiew vs. real numbers, right ?
Since you -from outside- can´t know all our uses. We have to summarise it up ourself i´d say.


i allready ordered my M4mini, with only 24GBs of RAM.
I run two displays right now, but want to up to 3 displays.
I´ve totally NOT considered that a 3rd display will eat up some RAM.
I´m now concerned.
i might still be able to change my order (tomorrow)

 

[wikeeboy]

I currently use a 14" M3 Max (14/30-core model) as my desktop machine connected to three Studio Displays. I've got 36GB RAM in my machine and it performs very well.

Activity Monitor generally has my memory usage at ~26GB and memory pressure in the green with my usual suite of apps running (Mail, Calendar, Safari, Edge, Discord, iMessage, Word, PowerPoint, plus a few background utilities like Dropbox, ChatGPT, Al Dente Pro, Smooze Pro and a handful of macOS desktop widgets).

Even when I use more memory-intensive apps like Parallels (for a Windows 11 VM allocated 8GB of RAM), Falcon MD and Osirix MD, I've never seen the memory pressure push itself into the red nor have I received "memory low" warnings from macOS. It does occasionally swap to the SSD in those situations, but it's so fast that I'd never know unless I looked at Activity Monitor.

Depending on what you're doing, you could certainly get by on 24GB, but if you're truly looking at three displays, I'm going to guess you're a bit of a power user, which in that case, 24GB might be pushing the lower limit.

The extra displays don't really put any additional burden on the CPU (aside from the apps residing on those displays), but the GPU does work to keep OS animations and such up to speed spread across all those extra pixels. However, I don't expect the M4 Pro's GPU to struggle with that (unless you're attempting to play a game spread across all three simultanously).

Appreciate your reply, your real world experience is very helpful with my situation.

I use many of the same apps as you, Outllook for Mail, Brave Browser with multiple windows and many tabs, Discord, Twitter/X Pro, Word, Excel, Music Streaming, YouTube Vids, TradingView. Nothing massively intensive. I day trade stocks and crypto hence the use of three screens.

If you're often around 26gb memory it puts me in that awkward position of either choosing 24 or 48gb of RAM. Annoying as i think 32 would have been perfect but the M4 Pro doesn't offer 32. The 48gb option is a significant price increase. Makes it a tough decision.

 

[xraydoc]

Appreciate your reply, your real world experience is very helpful with my situation.

I use many of the same apps as you, Outllook for Mail, Brave Browser with multiple windows and many tabs, Discord, Twitter/X Pro, Word, Excel, Music Streaming, YouTube Vids, TradingView. Nothing massively intensive. I day trade stocks and crypto hence the use of three screens.

If you're often around 26gb memory it puts me in that awkward position of either choosing 24 or 48gb of RAM. Annoying as i think 32 would have been perfect but the M4 Pro doesn't offer 32. The 48gb option is a significant price increase. Makes it a tough decision.

Don't forget that macOS will use RAM when it's available. Just because I've got 26GB in use doesn't mean it requires 26GB... it's there so macOS will make use of it. MacOS will swap things to the SSD when necessary, or will flush caches and purge closed apps out of RAM when free RAM is low. Otherwise, if RAM is available, it'll keep closed app in memory in case you open them again (note how sometimes closed apps will re-open in 1-2 Dock icon bounces and sometimes they'll re-open in 7-8 bounces).

My suggestion would be to buy and try the 24GB model and see. If you find constant yellow/red memory pressure, then you'll know you need more and you can return the machine within, what, 14 days. If memory pressure remains in the green, then you're good to go.

 

[xraydoc]

i´d like to know the very same thing as the OP.
But please, as numbers vs. what a 3rd display really will take.

How much load will one screen more add to the RAM ?
In my case 2K resolution.
What´s your, the knowledgable folks, estimation vs. a 2K screen, vs. a 4K screen vs. undemanding contents. Audio work in my case. While I would guess different usecases might change that RAM load. So much likely a very fluid thing vs. numbers ? and in that sense not easy to be answered ?


I consider statements like "this and that amount of RAM will be fine for you" not as an asnwer.
it is not answering the real query here.
"We", the unknowledgable, would like to get an overwiew vs. real numbers, right ?
Since you -from outside- can´t know all our uses. We have to summarise it up ourself i´d say.


i allready ordered my M4mini, with only 24GBs of RAM.
I run two displays right now, but want to up to 3 displays.
I´ve totally NOT considered that a 3rd display will eat up some RAM.
I´m now concerned.
i might still be able to change my order (tomorrow)

I don't think I've ever disconnected one of the displays and looked at the memory usage difference, but unless you're doing something GPU intensive, I don't think another display adds too much more to the RAM usage other than that display's framebuffer (which will depend on the resolution of the display -- 2K/4K/5K, etc).

 

[Gabebear]

Multiple displays matters because the hardware has to support that many DisplayPort interfaces, but for speed the total number of pixels is what matters.

Total pixels goes up exponentially as screen size increases:

• 2K: 2.2MP = 2048 x 1080 pixels
• 4K: 8.3MP = 3840 x 2160 pixels
• 5K: 14.8MP = 5120 x 2880 pixels
• 8K: 33.2MP = 7680 x 4320 pixels

You need more RAM per frame buffer and more RAM bandwidth to support the same frame rate.

 

[wikeeboy]

Don't forget that macOS will use RAM when it's available. Just because I've got 26GB in use doesn't mean it requires 26GB... it's there so macOS will make use of it. MacOS will swap things to the SSD when necessary, or will flush caches and purge closed apps out of RAM when free RAM is low. Otherwise, if RAM is available, it'll keep closed app in memory in case you open them again (note how sometimes closed apps will re-open in 1-2 Dock icon bounces and sometimes they'll re-open in 7-8 bounces).

My suggestion would be to buy and try the 24GB model and see. If you find constant yellow/red memory pressure, then you'll know you need more and you can return the machine within, what, 14 days. If memory pressure remains in the green, then you're good to go.

Thanks again, this is very helpful. Hadn't thought about the 14 day return policy. Also hadn't really thought about storage capacity on the SSD. I don't hold much locally, anything large like photos is cloud based. I currently have 256 on my MacAir and this seems ample so with the M4 512 should be plenty but it's a good reminder not to max it out.

I may just take your advice and try 24 of RAM and return if im pushing it in real use.

 

[wikeeboy]

Multiple displays matters because the hardware has to support that many DisplayPort interfaces, but for speed the total number of pixels is what matters.

Total pixels goes up exponentially as screen size increases:

• 2K: 2.2MP = 2048 x 1080 pixels
• 4K: 8.3MP = 3840 x 2160 pixels
• 5K: 14.8MP = 5120 x 2880 pixels
• 8K: 33.2MP = 7680 x 4320 pixels

You need more RAM per frame buffer and more RAM bandwidth to support the same frame rate.

Thanks for the reply. Would be very interested to see the effect on RAM switching from 2 to 3 externals, especially 3 Apple Studio displays.

 

[wikeeboy]

I don't think I've ever disconnected one of the displays and looked at the memory usage difference, but unless you're doing something GPU intensive, I don't think another display adds too much more to the RAM usage other than that display's framebuffer (which will depend on the resolution of the display -- 2K/4K/5K, etc).

Would love to see the change in RAM usage if you disconnect a display going from 3 down to 2 then back from 2 up to 3

 

[Mr.Fox]

I currently have an M3 MacbookAir 16gb. I only run 2 screens as it won't run 3 Apple screens (thunderbolt) simultaneously which is what i need.

CPU usage seems pretty low for my average usage, but my 16gb of RAM is constantly running at 14gb+.

The new M4 Pro Mini will now handle 3 Apple screens so i'm going to buy one but am wondering which CPU and RAM to select. On my current Mac Air if i was to hypothetically run an extra screen (3 in total) i'm trying to understand how much extra CPU or RAM this may gobble up. If i'm already using up 16gb RAM consistently, will adding an extra screen require much more or has this little to do with it? The M4 Pro comes with 24gb so quite possibly that extra 6gb will be enough. If not i can go for 48gb but it's a significant cost increase.

I'm assuming an extra screen running won't really tax the CPU/GPU?

Appreciate any advice and opinions.

Do not experiment in buying a computer with 24GB of memory to “see if it will pull or not”. The very load and very strong can give some software that can easily “hang” the computer, turning it into a kind of brick when using an additional screen when selecting 2K resolution and more. Get 48GB of memory. Yes, it is expensive, but it will be an insurance against such surprises.

 

[agregson]

Each display will allocate a framebuffer as does each window. Larger displays and more/larger windows require more memory. The WindowServer process reflects this. When I connect/disconnect external display or open/close windows the memory used by Windowserver changes to reflect all of the backing buffers.

 

[Gabebear]

The number of screens isn't a great measure of how much RAM you need. An 8K buffer uses 126MB of RAM (7680 x 4320 x 4 bytes). Depending on what apps you are using you may have as few as 2 buffers or as many as 1000 buffers per screen.

The total number of pixels you will be pushing and the type and number of apps you run will dictate how much memory you will need.