16 GB unified memory vs 16 GB RAM: How much better is unified memory quantitatively?

Unified Memory is a performance win. Lots more bandwidth, and no need to copy display data between memory and vram, as all that is needed is to pass a pointer to the GPU. And the memory chips being a fraction of an inch from the CPU/GPU reduces memory access latency, also a performance win.

Also the higher end Apple Silicon CPUs have even higher bandwidth.

The NVMe storage is very fast. Faster than your typical SSD, and again being on the motherboard, reduces the distance between the NVMe and the CPU, which reduces latency. So if you end up using page/swap storage, it is faster.

But more RAM is always a performance win over paging & swapping.

Also Chrome is not known for its resource efficiency. It is a known resource hog.

And having hundreds of open Chrome tabs just aggravates the situation.

So more memory would be good, unless you are going to reform your resource wasteful ways 😁

More efficient memory relates to the Unified nature of Apple Silicon chips.

Every component in the SoC (System on a Chip) has direct access to RAM:

• CPU
• GPU
• Neural Engine (machine learning/AI)
• Media Engine (Hardware-accelerated H.264, HEVC, ProRes, and ProRes RAW, Video decode engine, Video encode engine, ProRes encode and decode engine, AV1 decode)

That means less copying data from memory to the GPU and back, or the Neural engine, or the video encode/decode units. Instead, the code passes a pointer to the data in memory and the hardware unit processes the data in place.

As to memory bandwidth, it depends on which Apple Silicon chips you get, and how much RAM you include in your purchase. The lowest end is 100 gigabits/sec up to 400 gigabits/sec. But keep in mind less data has to be moved around, so you are using less of the bandwidth.

MacBook Pro - Tech Specs - Apple

Some personal observations.

I use my computers primarily for video editing 4K/1080p in Final Cut Pro and DaVinci Resolve.

I have the same iMac as you but refrained from upgrading the RAM from 8 GB because I found it was more than fast enough and from previous experience doubling RAM had no noticeable difference.

A year ago I bought the base model M2 mini (8GB RAM) and 256 GB SSD for £580 from Amazon.

The mini is at least twice as fast as the iMac in everything it does . . . that is it renders and exports etc. in half the time.

The 256 GB SSD was "cured" with a Crucial 1 TB SSD for £60 from which I boot the mini.

Although the Crucial is much slower than the internal it has absolutely no effect on the speed of the computer except for straight copying of massive files which I rarely if ever do.

As of today (over a year later) the internal SSD has only written 523 GB because all the work (and wear) has been done on the cheap Crucial..

Those are my observations but you are free to spend as much money as you wish . . . don't let me deter you from swelling Apple's coffers.

GummoMarx wrote:

How much better quantitatively is 16 GB of unified memory in a new Mac Mini over my 16 GB RAM on my 2017 iMac. Would 16 GB of unified memory take care of the sluggishness, long buffering, occasional crashing of Apple Mail and Chrome? Or should I go with 18 GB, 24 or 32 GB unified? Don't want to spend more than the cost of 16 GB unless really necessary.

Unified Memory means that the CPU & GPU (graphics processor) share the same memory ... the GPU does not have its own dedicated vRAM.

Your 2017 27" iMac has 4GB dedicated vRAM in addition to your 16GB system RAM. To be comparable, an Apple Silicon Mac would need at least 20GB Unified Memory. And while the Unified Memory in a new Mac will be faster than what's in your 2017 iMac, it will not necessarily overcome the problems you highlighted. Those problems are probably caused by things other than the amount of RAM, like your excessive number of Chrome browser windows.

As @den.thed said earlier, you might consider adding RAM to your 2017 iMac. You can go all the way up to 64GB RAM for a whole lot less $$ than buying a new Mac with 24 or 32GB RAM.

FWIW, the current version of Photoshop works perfectly fine on Intel Macs running macOS Monterey. That's my setup and I have not had any problems with Photoshop 2023 (24.7.5) or 2024 (25.4).

How much of the installed main memory are you using now, which Intel processor, what’s your target upgrade, what are the recommended system configurations for the apps you are using, etc?

You are correct, here. Memory bandwidth is absolutely one factor involved in performance. So too is the processor. So too is the speed of main storage, where the recent Apple silicon storage runs at roughly the same performance as DDR3; as did main memory from not that long ago.

If you’re using most or all of that 16 GB now, then get 16 GB minimally, and consider getting 32 GB because nothing* in the entire history of computing that is presently occupying memory has ever gotten smaller.

Apps getting slower as described can also point to Wi-Fi or wired issues or ISP network issues, or to app issues. Some apps just don’t scale and don’t run very well past some particular usage.

Recognize that computers are a system. That means the maximum performance achievable will be determined by the slowest component involved; of memory, processor, storage, network, etc. Slowest? Some folks wasted an I7 or i9 onto a hard disk configuration, for instance. That more expensive i7 or i9 probably got bored just waiting for data transfers with that hard disk, as massive memory caches can only mask some part of that performance difference.

Trade-offs abound too, as each storage level within a computer is a trade-off with cost and performance. Processor registers are massively fast memory, but also massively expensive. Processor cache is fast too, but expensive. Main memory is somewhat less expensive, and somewhat less fast. Main storage is far more voluminous, cheaper, and slower. And main storage is persistent too, where all the data in the faster storage can go “poof” when the main power goes “poof”.

Those trade-offs put differently for consideration, with Apple silicon, memory contents can be swapped out to main storage and back in far faster than a hard disk, so maybe less main memory is needed than when trying to cache your way around the performance of a hard disk.

TL;DR: Pragmatically, get the same main memory, and preferably get somewhat more main memory (and main storage) than you are using now, and preferably enough for the useful life of the Mac.

*approximately.

Just realised you have a carefree attitude towards leaving apps open when not required.

16 GB would "help" but you would be unlikely to notice the difference.

Only a Mac Studio with 128 GB RAM would be likely to work OK in your case.

You need to rein in the number of windows and apps you have open and you will find your iMac will buzz along.

Also get rid of Chrome . . . it is a well documented performance killer as it installs a Keystone that absolutely hogs your Mac's resources even when it is not running. See this article and how to get rid of everything Chrome has put on your computer . . .

https://chromeisbad.com/

Further performance problems can be caused by "cleaning" apps such as Clean My Mac and also anti-virus software that the Mac does not need.

I could go on but I have given you enough to worry about for the time being!

Incidentally my iMac is running Ventura and works perfectly.

It's late in the game, but your 2017 27" iMac can actually be upgraded to 32GB or even 64GB of RAM.

see > https://eshop.macsales.com/shop/memory/imac-2017-27-inch

While the unified memory in the silicon Mac's is much faster. You do not want to come up short, because the new Silicone Mac's including the Mac mini is not upgradable after purchase.

To future proof a new purchase, order the Mac mini M2 Pro with the 32GB and the 1T upgrades for $1900.

see > Mac mini - Apple

I have been using a 32” 4K DELL (which I ponied up the 💰 for), since 2019. It replaced a 27” 2K iMac display I had since 2009.

The iMac was replaced by a 13” Macbook Pro, and that was replaced by a 14” Macbook Pro with an M1 Pro CPU chip that I am currently using.

Recently I absconded with my Wife’s 28” 4K Acer monitor, rotated it 90° and set it up next to the DELL.

GummoMarx wrote:

MrHoffman, tbhank you for your eply. I do understand the "system" concept, but it is most difficult for me to determine which of many components might be at issue. But I do know is I have too many browser windows open and too many emails I have yet to delete.

If you want us to look at your current configuration, please post the EtreCheck data.

Otherwise, all I really wanted to know is how much better 16 GB of unified memory is over 16 GB of RAM, all other things more or less equal. Apple touts that unified memory is better (efficient?), but that is a qualitative description. I was looking for a quantitative answer.

Geekbench might interest.

But this is seemingly all still at the “lies, d*mned lies, statistics, and benchmarks” stage of discussion.

My 2017 iMac:

--processor: 3.4 Ghz quad core intel core i5;

--Memory: 16 GB, 2400 MHz DDR4;

--Graphics: Radeon Pro 570 4GB

--MacOS Monterey 12.7.6

--Hard drive: 1 TB

Hard drive? Really? If so, there’s your performance problem.

Maybe you meant SSD? Or maybe Fusion? (Fusion is a hard disk that can sprint.)

U3219Q 32” 4K monitor.

No webcam, no mike, no speakers.

I either use my Macbook Pro or my iPhone as the video, mike, speaker for Zoom meetings. And I do not have too many of those. I’m a file system software developer. Little need for face-to-face meetings, when Slack and email do all the heavy lifting.

The Acer does have speakers and they are horrible ☹️. The Mac speakers are much better.

I am not recommending the DELL, but at the time it had the brightest (nits) I wanted for office work, video ports, USB ports, and built in mini-KVM switching between 2 systems.

I did not need to worry about color quality, as writing code, just needs readability text, and while my code editor does colorize the code, it does not need to be faithful to the color of skin tones, trees, the sky, etc…. Brightness in a florence lighting office environment was more important to me.

Today, I might choose a different vendor. Plus the prices have come down. I might even look at an Ultra-Wide monitor and skip having the 2nd external display.

I’ve had the DELL since mid-2019 (5’ish years), and it is still doing well. It is used almost every day. It has also been on a UPS device, so it is both surge protected, and does not see most power outages, at least not the momentary ones. All my comm gear and other computers equipped is also on UPS devices.

GummoMarx wrote:

I still use a 2017, 27-inch iMac with 16 GB RAM and MacOS 12.7.6 Monterey. MacOS 13 I believe is the limit for this iMac, but I won't upgrade because I'm unsure it will work nicely with latest Adobe InDesign and Photoshop. I often prepare 88+ page InDesign magazine files and 250-page books for press quality PDF printing and use other misc software.

Plus, I have HUNDREDS of open browser windows in Chrome. Chrome is very slow downloading and halts temporarily while apparently buffering. Apple Mail also is very slow opening up and downloading mail; I have a lot of email sitting in the app.

…

How much better quantitatively is 16 GB of unified memory in a new Mac Mini over my 16 GB RAM on my 2017 iMac. Would 16 GB of unified memory take care of the sluggishness, long buffering, occasional crashing of Apple Mail and Chrome? Or should I go with 18 GB, 24 or 32 GB unified? Don't want to spend more than the cost of 16 GB unless really necessary.

Unified memory is RAM. RAM that is shared by the CPU, GPU, Neural Engine, and other computing engines on the Apple Silicon processor chip. Although using shared memory allows for some optimizations (e.g., an Apple Silicon Mac doesn't need to copy video data to and from the dedicated VRAM of a discrete GPU), and most Apple Silicon Macs have fast SSDs, I would hesitate to assume that you can get away with less memory on an Apple Silicon Mac just because of the change in CPU/GPU architecture.

Adobe recommends at least 16 GB of RAM for the Mac version of InDesign.

https://helpx.adobe.com/indesign/system-requirements.html

You say that you often prepare 88+ InDesign files and 250-page books, and that on top of that, you run Chrome – with HUNDREDS of open browser windows. It does not sound to me like 16 GB is adequate for that use case.