40 GB of RAM worth it?

72C-10

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Original poster
Jun 26, 2017
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I know a poll was done to see what RAM people would be running and many said they would buy the 32 gig kits and run 40 gigs total. Has anyone done this yet? Is it worth it to have 40 gigs?
 

Ph.D.

macrumors 6502a
Jul 8, 2014
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Rarely, actually. Memory usage in Mac OS is so well managed that most of the time the stock 8GB is fine for people. An SSD makes life with that little ram better, too.

But if you need it, you will know it. Watch your "memory pressure" in the Activity Monitor.
 
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macsplusmacs

macrumors 6502
Nov 23, 2014
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You need to list out your apps.

I went to 40 and it was cheap and I have so much more room now for my workflow.
 

trsblader

macrumors 6502
May 20, 2011
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It's only worth it if you actually use that much. For example, if your max workload is only using up 4gb of ram, then 40 would have no benefit for you. To know for sure, you should monitor your ram usage through the memory tab in activity monitor.
 

SaSaSushi

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Aug 8, 2007
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The more RAM you install, the more macOS will use it to try and improve performance. As mentioned above, in Activity Monitor > Memory if Memory Pressure is high and/or the system is paging/swapping to the SSD/HDD (Swap Used) then you would benefit from adding RAM. Also, if performance in general is poor (slow app launches, spinning beachball, etc) then it could be RAM deficiency-related. 8GB is not a lot but if you have minimal apps running and don't use VMs, etc then it is possible for it to suffice.
 
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glazball

macrumors member
Jul 5, 2017
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"Worth it" to have 40 GB, or 16 or 64... is totally subjective and really up to your budget. Put 64 in if you can afford it. You can never have too much RAM.

I am personally ordering 32GB for 40GB total which should last me the life of the iMac.
 
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fitshaced

macrumors 68000
Jul 2, 2011
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RAM is a bit like hard disk space. You don’t really want to run it close to the bone. I know I wanted 32GB for my iMac and so it made sense to get 2X16Gb modules which added up to 40. I can’t see me ever needing to max it out but I also didn’t want to waste the preinstalled 8. So, 4X8GB wasn’t what I wanted. Currently, I’ve been running Final Cut Pro X, Motion and a few Safari tabs simultaneously and not really going below 20GB. However, your usage might differ to mine and so you might use even less. But, 40 is about right for me. 68 would be a total waste of money.
 
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gian8989

macrumors 6502
Oct 23, 2015
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I know a poll was done to see what RAM people would be running and many said they would buy the 32 gig kits and run 40 gigs total. Has anyone done this yet? Is it worth it to have 40 gigs?
if you read the other thread about ram on the new imac you will see that if you bought faster ram than the apple one you will only get lower performance by using both ram.
What kit did you bought?
 

macintoshmac

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May 13, 2010
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I know a poll was done to see what RAM people would be running and many said they would buy the 32 gig kits and run 40 gigs total. Has anyone done this yet? Is it worth it to have 40 gigs?
Of course. What's 40, all Apple computers, from the top tier Mac Pro to the nifty portable MacBook should have come with 64GB RAM standard already.
 
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hagar

macrumors 6502a
Jan 19, 2008
797
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If you need to ask, then no.

If you're an average user 16GB is plenty. If you run a lot of pro software and virtual machines, 32GB will improve performance. 32+GB is in most cases, a waste of money.
 

jerwin

macrumors 68030
Jun 13, 2015
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The more RAM you install, the more macOS will use it to try and improve performance.
Up to a limit. A 10 GB file cache tends to be highly speculative.
Programs may not be written to take advantage of extremely large amounts of memory. I'd think that fsck_hfs would like to use more than 3GB of memory (to store deeper trees and other more elaborate data structures), but no.
Safari, with a couple dozen tabs might use 8GB.
From what I can tell. Abbyy Finereader, divides the workload among 4 processes, each using a gigabyte... Might be different with a hyperthreaded processor, or a cpu with more than four cores...

Photoshop, and a few other adobe products like to grab enormous amounts of ram for themselves, but whether it amounts to a speed advantage depends on the circumstances.

Remember, good programmers are careful about memory usage. A scheme that deliberately uses more memory in order to produce a speed advantage must be carefully profiled.

Virtual machines tend to require the most amount of memory, but then you might have to consider whether the VM really needs all 8 GB, or 16 GB, or can do the job with 4 GB...

40 GB is an enormous amount of RAM, and if it ends up being slower than the stock 8GB due to a timing mismatch you'd probably notice the slowdown, before you'd notice the effects of having more.
 
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JasonMovieGuy

macrumors regular
Jan 11, 2010
116
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Chicago, IL
Wait what?? How is 40GB going to slow down your computer more then the 8GB? That's not making sense at all. Timing mismatch? Never heard of it. I'm not at all trying to come off crass, I just need further insight. Especially if I'm about to spend money on all this ram and it turns out I don't need to.
 

macintoshmac

macrumors 68040
May 13, 2010
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Wait what?? How is 40GB going to slow down your computer more then the 8GB? That's not making sense at all. Timing mismatch? Never heard of it. I'm not at all trying to come off crass, I just need further insight. Especially if I'm about to spend money on all this ram and it turns out I don't need to.
RAM has speed and latency figures. This "timing" that we talk is latency, also otherwise known as CAS. Speed is 1600MHz 1866MHz 2133MHz etc.

What you need to do is match all the sticks you stick in your computer. Get the lowest possible latency with the highest possible speed your computer can support.

Now, buying higher latency means observable snappiness differences can occur. More than the perceptible difference in bus speed. A slower latency will be more noticeable than a faster speed.
 
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JasonMovieGuy

macrumors regular
Jan 11, 2010
116
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Chicago, IL
So in other words, don't get the 16X2 sticks (32GB) to add to the preinstalled ram Apple has, because they put in 2X4GB? I'm still not following, sorry. Everyone has reported they added RAM with the 32GB kits and their machines run just fine. This is just confusing.
 

macintoshmac

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May 13, 2010
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Could you post the photos of both sides of the sticks you are currently using, and the sticks you wish to buy/ have bought already?

Do not scrimp on RAM purchases from a quality company. Go OWC or Crucial Mac and you will get guaranteed compatibility.
 
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gian8989

macrumors 6502
Oct 23, 2015
273
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So in other words, don't get the 16X2 sticks (32GB) to add to the preinstalled ram Apple has, because they put in 2X4GB? I'm still not following, sorry. Everyone has reported they added RAM with the 32GB kits and their machines run just fine. This is just confusing.
The ballistic & hyperX ram are faster than apple ram (cl14,15 for hyperX, cl17 for apple ram) so using both will slow down the faster one. Some people had also speed reduced to 2133 instead of 2400. This is why it is better to remove apple ram if you buy 16x2 kit and if it is faster than apple (i think crucial is the same as apple both in speed and cl).
 

SaSaSushi

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Aug 8, 2007
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The ballistic & hyperX ram are faster than apple ram (cl14,15 for hyperX, cl17 for apple ram) so using both will slow down the faster one. Some people had also speed reduced to 2133 instead of 2400. This is why it is better to remove apple ram if you buy 16x2 kit and if it is faster than apple (i think crucial is the same as apple both in speed and cl).
If the Apple RAM is slowing down my Ballistix the benchmarks don't show it. All 40GB, including the Apple RAM is running at 2400MHz. Take it from someone who is actually using it.

The 2133MHz problem with Hyper-X RAM is due to the fact that the Kingston RAM is overclocked.
 
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kschendel

macrumors 65816
Dec 9, 2014
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I'm not sure 40 Gb is cost effective. I might be inclined to go with an additional 16 (2x8) for 24 Gb total. On the other hand if you can get a 2x16 kit for a reasonable increment, and it's the right RAM, I can't think that it would hurt.

(Technically, additional RAM isn't free as far as the OS is concerned. Tracking RAM usage requires page tables and other data structures which grow with physical RAM. I don't know how OS/X does it, but any rational OS will arrange things so that the physical RAM data structure time overhead is minimal if you aren't actually using it for anything useful.)
 

JasonMovieGuy

macrumors regular
Jan 11, 2010
116
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Chicago, IL
(Technically, additional RAM isn't free as far as the OS is concerned.
What do you mean it isn't free? If I want to add to the additional ram included by Apple, the slots allow it. The OS will certainly recognize it, and thus I should have 40GB of RAM.

Explain this "Isn't Free" one, because I'm hearing all sorts of crazy theories today.
 

kschendel

macrumors 65816
Dec 9, 2014
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All I mean is that the OS has to be aware of the RAM that exists. Typically this is done via some sort of data structure that grows with physical memory. The more RAM, the larger this data structure is, and done naively, the longer it might take to perform operations on that data structure. A naive OS which doesn't expect large physical memory might use a data structure that is time intensive based on size. A properly written, modern OS will use algorithms that scale with physical memory actually in use, and not physical memory that exists in the hardware. I would expect that OS/X, being a modern operating system, will use a data structure and corresponding algorithms that scale with memory in use, and adding memory beyond what can be effectively used will have little to no effect.
 
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