do I want more memory in my iMac Retina

More memory on a Mac never hurts. I have not run a mac on anything less that 16GB. I frankly don't get how 4 or 8 is adequate unless there is NO choice.

 

Personally, all my Macs have 16GB of RAM (except my MacBook Air), but I can comfortably run a VM and work on a Photoshop file at the same time without any lags at all.

With RAM compression and caching, free and used RAM values are irrelevant. All that matters is the RAM pressure graph. These two technologies can make 8GB of RAM act more like 12-14GB of RAM before swapping happens.

 

At a minimum I would match the 8GB stick that's already in there. You can grab a matching 8GB stick from eBay for about $40. Then you'll still have two slots to upgrade in the future.

 

I guess an iMac will last very long; so I had put 32Gb in it.
By the time it is old I will need it, with respect to software 'development'.
My first PC was 512Kb, my boss was reluctant to add another 512Kb
but today you need at least 16Gb, so .......
;JOOP!

 

ram is cheap so max it out.

no ram pressure means less cycles for the cpu. more files cached etc.
make it smooth.

 

I doubt you'll see any difference having more than 8-16gb of RAM, unless your apps demand it, which I doubt. You'd see more gains from a faster CPU and GPU, neither of which can be upgraded

 

Going from 8 GB to 16 GB with the momentus XT in my 2011 MBP was decent improvement in system speed due to the additional disk caching OS X does. Even when not pushing the machine hard. I was surprised. It was just in general snappier. But it was far, far less than the difference between 4 GB and 8 GB.

I suspect 24 GB may be overkill for what you do, but hey, 16 GB worth of RAM is pretty cheap now (2x8 is not much more than 2x4 really), if it fits you may as well do it.

You'll definitely notice the difference between 8 GB and 24 GB that's for sure.

Not quite. Even if your pressure graph is not showing memory pressure, more RAM beyond that does provide more headroom for disk cache, which on a non-SSD machine makes a large difference.

But yes, free and used are not that relevant. But more RAM does help even if there's not "pressure"...



edit:
Also - your current memory - is it 2x4 or 1x8?

If it is 1x8, then make sure to add another 8 GB stick to it before adding anything else. Always maintain an even number of modules in total, because otherwise the CPU can't access 2 channels at a time, and it has a 2 channel memory controller...

 

If your memory pressure never goes yellow or red, there is no reason for you to upgrade the RAM.

 

People keep saying that, but based on personal experience, i've never seen the memory pressure gauge anything other than green with both 8 GB and 16 GB, and 16 GB is definitely faster if you're not running from SSD...

I originally upgraded from 8 to 16 to run some larger VMs, and noticed the difference immediately before firing any of them up.

 

I don't believe this is really true. Compression certainly comes at a cost. Nothing beats actual memory.

 

I agree.

 

The 2 GB in my MacBook Air is adequate for certain tasks. I'm actually surprised at how long it will last on Yosemite without needing much swap.

The OS can cache more to free RAM, so that might make it seem a little quicker.

 

To add on to throAU's comment, I recently moved from a machine with 512MB of VRAM and 16GB RAM to one with double those amounts. On the new machine, I can keep every app I use open, and also not experience any hesitation when invoking Mission Control or switching spaces. The new machine also has a spinning HDD, and having more memory made a noticeable difference for me.

The Mac uses more cache in the 32GB configuration than it did in the 16GB configuration. In my workflow, the Mac now never uses more than about 25GB of RAM, including cache. I think I have found the RAM "sweet spot" for my own workflow, but your own mileage will of course vary.

 

I had 8GB in mine for a few days. I put 32GB of 1866 in. While you may not need 32GB or even 1866, the upgrade from 8 certainly feels smoother. 32 is certainly overkill for me but even going to 24 would be a benefit for you I believe.

I am not doing anything memory hungry ATM, but Memory used is 8.48 with with a 19.90 GB cache

 

Wow is Yosemite that efficient with memory? I'm still on Mavericks with a 8GB Macbook Air and I've had memory issues plenty of times with mutiple tabs/browsers open. Sometimes Chrome and Firefox acts like a pig

 

I have iMac i5/m290x with 24 GB. Personally ive never remotely came close to hitting the 24 GB limit but I don't regret putting it in since it's pretty cheap upgrade and i'll never have to worry about it in the future.

i'd go with at least 16GB and at worst you'll be burning another $60 if you went with 24 GB

 

Look at all your software, find the one with the highest recommended RAM and go with that.

Being that's the iMac is quad core you'll have diminishing returns passed 24gb and that's if you are a pro user using Adobe creative suites rendering 4k while concurrently trying to edit something else.

4K



1080p has no benefit.

 

Imho I think that you should upgrade the ram, now or later.
Every app developed nowadays needs more and more ram to work better - smoother.
Your iMac will run better with any app , even os x benefits from plenty of ram, the same stands for aperture, safari, preview, games.

You 're also eliminating and the need for use the swap file, and the necessary wear of your hd / ssd.

In the case of ram it's better to have more than less.

The ram compression in os x is a good thing but not a substitute for the real thing.
Regards,

P.S. for monitoring
You can use istat menus, (better)
http://bjango.com/mac/istatmenus/

or the os x built in app: activity monitor (only for current use)

 

Activity monitor will tell you how much ram you are using.

Subtract the "cached" amount from the total in use, as that is for lessening storage activity, and the "cached" figure will keep growing to use all available RAM as you open and close files and applications. Cache will be cleared as required so it doesn't really count as memory in use that can't be used by other stuff.

Thats how much is use by the OS and applications. However, more cache is always better. Any unused RAM you have will be used for cache. Cache has diminishing returns though - stepping from 4-8 GB RAM gives you much more benefit from cache than going from say 8 to 16 GB (again, for most non-special case workloads).

Basically RAM usage for typical basic application use in OS X goes like this:

2 GB - you will hit swap doing basic stuff - if you have SSD you won't notice much, if you have a hard drive it will suck
4 GB - you will be able to run mostly out of swap doing basic stuff. with a hard drive it will suck.
8 GB - you will mostly not hit swap doing basic stuff and you will have 3-4 GB usable for cache to make things faster. if you have a hard drive, this will be a massive step up in performance from 4 GB. SSD not so noticeable. Popping 8 GB in my 2011 MBP (hard disk) boosted performance (loading apps, etc.) considerably.

Beyond that, it's all going to be cache which will speed things up. I noticed a performance improvement in my MBP going from 8 GB to 16 GB in general use, but nowhere near the step from 4 to 8 for most stuff.

If you're editing large videos, using virtual machines, or other uses that deal with multiple GB files, more RAM up to and and beyond 16 GB will help. It really depends how big your data sets are.

16 GB is probably the sweet spot in terms of $/performance for a Mac with 4 available slots (like an iMac - because 4 GB modules are very cheap now) for most people who aren't doing really heavy work. 32 GB isn't that expensive these days either if you're dealing with 4 slots, but probably overkill for most people.


edit:
and yes, memory compression can help with RAM shortages, but it doesn't come free. While your CPU is compressing and decompressing RAM, it isn't doing useful work...

 

Be very careful with saying things like "no benefit", based on application memory consumption graphs.

More memory beyond those figures will give you more cache. If you run something else at the same time, or are using a hard drive, your application trying to use 16 or 24 GB will start causing your Mac to purge things from cache. Which means they need to be re-read from disk. Again, if you're on SSD this isn't such a big problem these days, but if you have a hard drive, or are using hard drives for bulk data storage, you will take a hit to IO performance. And even with SSD.... SSD reads in terms of gigabytes per second on new Macs. RAM (cache) access speed is hundreds of gigabytes per second or more.

More RAM is ALWAYS better (in terms of overall system throughput, not just one application), but how much better tails off beyond a certain point depending on how much data you're dealing with. It's obviously also more expensive. But given you can pick up 16 GB for under a hundred bucks these days, it just doesn't make sense to skimp on memory (i.e., run less than 8 GB or so) if your Mac has slots.

But yes, I agree - for most people, unless you have a very specific usage scenario, beyond 8-16 GB at the moment is probably overkill.

But if you're talking 4 GB - upgrading to 8 GB will give you essentially 3x as much RAM for apps. Because OS X itself and a small amount of cache will consume 2 GB pretty easily... leaving 2 GB out of a 4 GB machine left. an 8 GB machine will have 6 GB left... 3x as much...

 

I am going to take a different tact.

Your computer right now is NEW. It has 8gb of ram and it seems to work OK for right now. I can imagine that you are going to want to keep this riMac for the next 4-5 more years. In that time will the amount of memory that is required increase? YES!

The next iteration of intel chips are moving to a new DDR4 standard. So supply and demand is clearly going to drive up the price of DDR3 memory just as it has for DDR2 and DDR1 when the new memory standard comes out. Right now a mac compatible 8gb dimm is pretty cheep. Compare that to an 8gb DDR2 and you will see that in a year or two the cost of memory upgrades for the type of memory your new riMac takes will shoot up to double? tripple? as the supply of this memory decreases because lower demand and less manufacturing.

Are you better to buy it now when you don't need it so you have it for when you do? Or save the dollars that you would spend now and hope it doesn't cost too much more in the future when you do need the memory.


BTW: I have a mac mini circa 2012 that came standard with 4gb of ram. Mountain Lion runs fantastic on it. Maverick works well. Yosemite just crawls with constant beachballs and issues. Bump that memory up to 8 or 16 and it works fine. It may be possible to work with less memory but it doesn't mean that it will work well. Dont fool yourself into thinking that RAM requirements for the OSx are going to stay constant for the next 5 years. If you don't plan on ever upgrading anything and just stick with the base OS that shipped you will be fine.

 

Yup.

16 GB of RAM (DDR3) is under 100 bucks today. It will speed some things up today. If you wait 2-3 years before upgrading, you've missed all that time with improved performance and the RAM isn't going to drop below half that cost (RAM modules tend to go out of production before they drop that much more than those already have), and as above, may well go up in price with DDR4 on the horizon.