Why 8/16GB RAM might not be an issue

[moosinuk]

Just a thought I had and no proof at this point in time.

Apple stated that the SSD'd in these new machines are up to twice as fast, so I went looking for the current Mac SSD speed and found this thread: https://forums.macrumors.com/threads/2020-imac-ssd-speeds-512gb-and-1tb-or-greater.2250057/

From this thread the read speeds range from 2250 MB/s to 2750 MB/s approximately, albeit for an iMac.

Given we are told up to twice as fast, we might be able to expect speeds of between 4500 MB/s (4.5 GB/s) and 5500 MB/s (5.5 GB/s).

So here's my thought, with those speeds memory swapping (paging) would be extremely fast and therefore could negate the limitations on the RAM. Yes, I know RAM is still faster, but pre-emptive swapping would remove a lot of negatives people have.

Anyway, just a though for discussion.

 

[johnhackworth]

Looks like the A14X Bionic has 42.7 GB/s memory bandwidth so I'm not convinced that a quick SSD will really make paging much more acceptable on a memory constrained M1-based system.

 

[michelg1970]

I hate to temper your expectation but on Apple.com it says for the MacBook Air that speeds are "up to 2x faster" with a reference to the following footnote:

Testing conducted by Apple in October 2020 using preproduction MacBook Air systems with Apple M1 chip, as well as production 1.2GHz quad-core Intel Core i7-based MacBook Air systems, all configured with 16GB RAM and 2TB SSD. Tested with FIO 3.23, 1024KB request size, 150GB test file and IO depth=8. Performance tests are conducted using specific computer systems and reflect the approximate performance of MacBook Air.

I don't know the speed of that reference machine but it might be less than half of the 5 GB/s you mention. Also, for the MBPro Apple says "up to 3.2 GB/s" so expect the Air to be less than that.

 

[deeddawg]

Just a thought I had and no proof at this point in time.

Not to be a cynic, and I do agree with you in principle, but it won't quell any of the back and forth discussions here for two basic reasons:

• Real world RAM utilization spans a wide spectrum; particularly in instances where a system begins utilizing swap. The experience of a user infrequently switching between quiescent apps (infrequent swapping) will be different from the experience of a user constantly switching between apps and/or the apps remain particularly active in background, thus driving frequent swapping perhaps to the point of thrashing.
• Many MacRumors members have an inflated idea of what many/most people actually use/need.

 

[theluggage]

Given we are told up to twice as fast, we might be able to expect speeds of between 4500 MB/s (4.5 GB/s) and 5500 MB/s (5.5 GB/s).

The "2x" increase most likely refers to peak, sustained read speeds - which are rarely reached in practice unless you're copying/streaming large files. The effect of swapping on performance will also be affected by seek and random access read/write times. The big, night-and-day, improvement on swap performance came with the initial switch to SSD (which has seek times an order of magnitude better than a mechanical HD) but Macs have had pretty fast PCIe SSDs for years now, so any further improvement is likely to be incremental. There may also be some situations where - between faster SSDs and new acceleration hardware on the M1 chip - the need to cache/buffer data in RAM is reduced, but that will be highly dependent on exactly what you are doing and what software, file formats etc. you are using.

Now, one reason for adding "more RAM than you need" is that MacOS will use "spare" RAM to cache regularly used data from disc. So, yes, faster SSD will reduce the impact of less cache space - but RAM access speed is still vastly faster than any SSD so having stuff cached in RAM is still better.

There is very unlikely to be any massive systematic reduction in RAM requirements - certainly not enough to make 16GB "as good as" 32GB or more. However - as @deeddawg says, many people get more RAM than they need (esp. on iMacs and Mac Minis where cheap DIY RAM upgrades are possible and there's no need to skimp). If you really need 32GB it is because you need to have gigabytes of data pre-loaded into RAM for fast access (large bitmaps for compositing in Photoshop, sound-sample banks in Logic, multiple virtual machines with large RAM quotas...) or maybe you just haven't found the "close tab" button and bookmark bar in Chrome...

Also, to repeat yet again, the previous Intel MacBook Air and MBP models at the same price-points as these M1 machines are replacing also maxed out at 16GB RAM... and the GPU in the M1 is stunningly impressive compared with other integrated GPUs - If you genuinely need 32GB or more of RAM (in which case it is likely that you also want more Thunderbolt ports, 10GB Ethernet, support for more displays, desktop discrete-GPU class graphics etc.) you should probably be waiting for Apple to replace the higher-end MacBook Pros, 5k iMac etc.

It's entirely possible that a 16GB M1 Air will out-perform an Intel Mac with 32GB+ on your workflow - but in a few months time it will probably be shredded by a 32GB M2/M1X/M1 Pro/whatever.

 

[bill-p]

Just a note: iOS does not have swap. Its more limited memory is acceptable because of tight memory management.

Also another note: ever since retina displays were introduced on Macs, @2X graphics assets take up 2x the amount of storage/memory and up to 4x if they are decompressed in memory. It makes sense because retina displays are 4x the resolution of whatever came before...

Believe what you will, but I've seen how Safari uses RAM in Big Sur:

And seeing that I need to run Capture One from time to time, I know I need 16GB of RAM. Even at 16GB, I've already hit 10GB swap.

I probably won't need 32GB of RAM, but honestly, I think 8GB is too little for my use case. And I don't think 2 browser tabs, 1 email app, and 1 photo editing app can even be considered "heavy usage".

P.S.: here's a thought: perhaps it's not that we are "exaggerating" RAM usage, but that you guys who think 8GB is enough is seriously underestimating how well-optimized some websites are. Look at Facebook.com. It's 1.3GB just sitting there in the background.

 

[moosinuk]

Not to be a cynic, and I do agree with you in principle, but it won't quell any of the back and forth discussions here for two basic reasons:

I totally agree with your comments.

If you genuinely need 32GB or more of RAM

I never mentioned any RAM requirements, although I do agree with your thoughts.

I was just thinking about pre-emptive swapping and how the possible speed increases in the SSD might assist those users who are thinking the current RAM offers might not be sufficient.

Thanks for all the comments.

 

[dmccloud]

Just a thought I had and no proof at this point in time.

Apple stated that the SSD'd in these new machines are up to twice as fast, so I went looking for the current Mac SSD speed and found this thread: https://forums.macrumors.com/threads/2020-imac-ssd-speeds-512gb-and-1tb-or-greater.2250057/

From this thread the read speeds range from 2250 MB/s to 2750 MB/s approximately, albeit for an iMac.

Given we are told up to twice as fast, we might be able to expect speeds of between 4500 MB/s (4.5 GB/s) and 5500 MB/s (5.5 GB/s).

So here's my thought, with those speeds memory swapping (paging) would be extremely fast and therefore could negate the limitations on the RAM. Yes, I know RAM is still faster, but pre-emptive swapping would remove a lot of negatives people have.

Anyway, just a though for discussion.

All of the new Macs are using PCIe 4.0, which allows for significantly higher bandwidth over 3.0. I know that you can buy M.2 SSDs capable of 7000 MB/s that take advantage of the bandwidth offered by PCIe 4.0, and I've seen some server-class M.2s that break the 10,000 MB/s threshold. While this has no bearing on just how fast the SSDs in these new Macs are in practice, it does mean that even if they hit 5500 MB/s now there is still room to increase speeds down the line. The issue with using the SSD as a page file would be that it still goes through the system I/O instead being on the SoC itself, so while faster than a traditional HDD, there would still be a performance hit compared to the onboard RAM.

 

[bobnugget]

If I was buying one of these systems today I would want more RAM to futureproof the machine a little. 16 GB is a minimum today for pro use.

I don't want a disposable computer that I'm going to replace in a few years time, so would definitely want a system with 32 GB RAM or ideally 64 GB, so it won't be slow and need replacing in 5 years. I probably differ from some of the macbook air target market there

Case in point - my 2012 15" MBP - perfectly fine in 2012 with 4 GB of RAM, eventually upped to 16 and it still runs like a champ today with an SSD in it. I recently used a near identical machine with 4 GB in and it seemed incredibly slow. I'll be waiting for the next gen in case we get a similar situation to the first intel machines.

Exciting times, anyway, the benchmarks are fantastic! The initial presentation underwhelmed me, but these new machines look as good as promised; I look forward to people's reports once they are released!