Apple iMac memory upgrade

[dave2010]

We have an iMac 27 inch Retina 2019. Sometimes it gets slow.

It only has the 8Gbytes of main memory it came with - checked in About This Mac.

My understanding is that the Crucial upgrades should work with this model.

Looks like there are 4 slots, so to take it up to 32 Gbytes would presumably have to take out an 8Gbyte module, and put 4 x 8 Gbyte modules in.

I could source these from Crucial for about £120.

My gut feeling is that if I can do this, that would make a significant difference to the performance of the machine.

I could also buy yet another offline storage device, and back up a lot of the files on the SSD which are cluttering it up, though I don't know how significant that would be in terms of speed up.

I think one or two people round here have done this kind of upgrade on a similar iMac.

Even though the M1 iMacs may be faster, I don't think I can reasonabaly buy yet another computer - and I do like the 27 inch display of this one

[struth]

more the merrier memory wise. yes it will help, if memory is your issue. certainly wont do any harm if it can take the upgrade. for 120 notes its worth trying

[dave2010]

more the merrier memory wise. yes it will help, if memory is your issue. certainly wont do any harm if it can take the upgrade. for 120 notes its worth tryingDifficult to know whether memory is an issue or not, but it seems likely. That has worked with previous models, though there does usually come a point at which it makes hardly any difference at all - as other channels - bus and IO eventually limit performance.

The thing to avoid is any memory swapping for active programs.

Anway £120 is a lot less than the cost of a new machine, and I've already said I like this one.

[struth]

Difficult to know whether memory is an issue or not, but it seems likely. That has worked with previous models, though there does usually come a point at which it makes hardly any difference at all - as other channels - bus and IO eventually limit performance.

The thing to avoid is any memory swapping for active programs.

Anway £120 is a lot less than the cost of a new machine, and I've already said I like this one.

you can always use memory elsewhere or sell on so trial comes at little cost.

[dave2010]

you can always use memory elsewhere or sell on so trial comes at little cost.I think Crucial offer a guarantee in case it doesn't work.
I would expect some improvement in any case, which would justify the cost. It should be possible to have two bites at this - a half way upgrade for around £60, and then go back for more it that worked, but is it worth the bother of opening up the machine twice? Perhaps not!

[AJSki2fly]

Difficult to know whether memory is an issue or not, but it seems likely. That has worked with previous models, though there does usually come a point at which it makes hardly any difference at all - as other channels - bus and IO eventually limit performance.

The thing to avoid is any memory swapping for active programs.

Anway £120 is a lot less than the cost of a new machine, and I've already said I like this one.

Used to work for Apple in tech support working on these, presumably you have regularly get up to date with the MAC OS and are running the last compatible MAC OS for it, this will use significantly more RAM than the MAC OS that came with it originally, and 8Mb of RAM is not going to cut it, especially if you start having multiple Apps running simultaneously. So going to 16Mb of 32Mb of ram should help, question is is it worth it?

With respect to the onboard Hard drive, has it ever been replaced, most spinny hard drives last for 5-6 years before failing and needing to be replaced, sticking an SSD external HD and moving data file to it may help, but the limiting factor with be the speed of the USB bus, be careful with external SSD drives, not all will work with a machine of your spec, some require different low level read/write software and you machine may not support that, I know this is fact due to a customer that had an SSD put in his iMac, it would install and load the OS and then would fail, it took some investigation to get to the bottom of the problem.

My advise is this.

1. The old Hard Drive may be getting disk errors and starting to fail, this will slow the machine up. Back it up to an external Hard drive FIRST. and then run disk utility on the internal hard drive and see if its has error or fails. If it fails or is old and has errors, consider if you wan to spend money on an old machine, it is now unsupported and parts will become unavailable if not so already.

2. If you get past 1, and you want to spend money on it, then put the external RAM in at least 16Mb match pairs(8Mb each) and ensure they go into the correct Ram bays, there is documentation on this, if you put them in the wrong bays then the machine will either not see one or the other or run slow. If 32Mb then 4*8Mb sticks one in each.

3. Consider that cost of the above, any repair to a 2019 iMac, will not be cheap, a LCD will probably set you back around £300-400 replacement possibly more and the MLB(logic board if available around the same. The PSU is/was around £100 plus repair cost so about £200 if it fails. I think the graphics cards are £200-300 plus fitting of around £100. If you do not want o face such a possibility then buy a new Mac.

I hope that helps a bit.

[rmcin626]

Adrian, gave some good advise when I bought my IMAC about 18 months ago, has been running well since day 1.

[dave2010]

My advise is this.

1. The old Hard Drive may be getting disk errors and starting to fail, this will slow the machine up. Back it up to an external Hard drive FIRST. and then run disk utility on the internal hard drive and see if its has error or fails. If it fails or is old and has errors, consider if you wan to spend money on an old machine, it is now unsupported and parts will become unavailable if not so already.

2. If you get past 1, and you want to spend money on it, then put the external RAM in at least 16Mb match pairs(8Mb each) and ensure they go into the correct Ram bays, there is documentation on this, if you put them in the wrong bays then the machine will either not see one or the other or run slow. If 32Mb then 4*8Mb sticks one in each.

3. Consider that cost of the above, any repair to a 2019 iMac, will not be cheap, a LCD will probably set you back around £300-400 replacement possibly more and the MLB(logic board if available around the same. The PSU is/was around £100 plus repair cost so about £200 if it fails. I think the graphics cards are £200-300 plus fitting of around £100. If you do not want o face such a possibility then buy a new Mac.

Thanks for the comments. The drive is a 1 Tbyte Fusion - which I think is a 1 Tbyte HDD, plus a small amount of SSD - perhaps 100 Gbytes. Earlier Fusion drives had a better ratio of SSD to HDD, then Apple got mean.

Would a Time Machine backup be good enough before checking out the HDD, or should I use yet another HDD as a backup and (say) Carbon Copy Cloner?
I have tended to think of TM as not really being much use - but it did rescue my laptop a few years ago when a bad driver for a webcam which I wanted early on in the pandemic lockdown, trashed the machine.
I have it running, but whether it's really worthwhile I'm not sure.

I have other machines (iMacs and a few others) which date back way beyond 2011, and they still work. However, I have also seen iMacs go bad - though not generally within 5 years of purchase.

I'd really like to keep this one [around 3 year old...] going - I think the only obvious issue is the lack of main memory - and maybe more SSD would be nice too, but that's a more difficult "upgrade"/repair. Solution to the SSD issue is to simply back off all less used and less wanted data to external hard drives. I'm not sure if there's a way to purge unwanted files which are backed off, or if "dead" copies just lie in there causing slowdown issues from time to time.

I do tend to have loads of programs loaded at any one time, so my gut feeling is that more memory would be a sensible way to go.

If the machine dies I will replace it, but I'm hoping it'll go for quite a few more years yet. My Macbook Pro is now 8 years old, and despite some minor issues, it still serves me well. I just wish it had more SSD, but costs at the time of purchase, and current cost of repair/upgrade tend to counter any activity to remedy that. I'll probably buy an M1 or M2 machine in due course.

[AJSki2fly]

Thanks for the comments. The drive is a 1 Tbyte Fusion - which I think is a 1 Tbyte HDD, plus a small amount of SSD - perhaps 100 Gbytes. Earlier Fusion drives had a better ratio of SSD to HDD, then Apple got mean.

Would a Time Machine backup be good enough before checking out the HDD, or should I use yet another HDD as a backup and (say) Carbon Copy Cloner?
I have tended to think of TM as not really being much use - but it did rescue my laptop a few years ago when a bad driver for a webcam which I wanted early on in the pandemic lockdown, trashed the machine.
I have it running, but whether it's really worthwhile I'm not sure.

I have other machines (iMacs and a few others) which date back way beyond 2011, and they still work. However, I have also seen iMacs go bad - though not generally within 5 years of purchase.

I'd really like to keep this one [around 3 year old...] going - I think the only obvious issue is the lack of main memory - and maybe more SSD would be nice too, but that's a more difficult "upgrade"/repair. Solution to the SSD issue is to simply back off all less used and less wanted data to external hard drives. I'm not sure if there's a way to purge unwanted files which are backed off, or if "dead" copies just lie in there causing slowdown issues from time to time.

I do tend to have loads of programs loaded at any one time, so my gut feeling is that more memory would be a sensible way to go.

If the machine dies I will replace it, but I'm hoping it'll go for quite a few more years yet. My Macbook Pro is now 8 years old, and despite some minor issues, it still serves me well. I just wish it had more SSD, but costs at the time of purchase, and current cost of repair/upgrade tend to counter any activity to remedy that. I'll probably buy an M1 or M2 machine in due course.

"The drive is a 1 Tbyte Fusion - which I think is a 1 Tbyte HDD, plus a small amount of SSD - perhaps 100 Gbytes."

Fusion drives are a pain in the proverbial IMO, and experience, the idea was to put the core OS system files on the SSD and allow it to be used for memory page swapping, if I recall correctly. The main aim to improve machine speed, but it is somewhat limited, especially if you only have 8Mb Ram. Be careful with a fusion drive they are known to fail, I seem to remember that there was an Apple recall to replace the SSDs on fusion drive machines, you should be able to check this online on Apple by entering your machine Serial Number.

"Would a Time Machine backup be good enough before checking out the HDD"

Only use a Time Machine backup just make sure it is up to date before doing HDD check.

"I have tended to think of TM as not really being much use"

Never rely on Cloud or other backups for Macs, you should have one connected all the time to every Mac you have, then if any fail after fixing /replacing recovery is simples!

"I'm not sure if there's a way to purge unwanted files which are backed off, or if "dead" copies just lie in there causing slowdown issues from time to time."

Managing unwanted files is down to you I am afraid, if you know what they are then delete them, if you accidentally delete them then there is a way to get them from the earlier backups from the Time Machine backup history, another good reason to use it. By the way if your Time Machine backup drive fills up then it will start dropping off old copies/backups, so if you never want to worry about it then it is best to spec the Time Machine backup drive at least twice the size of ALL the Macs hard drives that are being backup to it.

"I do tend to have loads of programs loaded at any one time, so my gut feeling is that more memory would be a sensible way to go."

As I said before 8Mb with the most recent versions of Mac OS is nothing, and if you open loads of Apps they will be memory page swapping like hoares draws.

"The drive is a 1 Tbyte Fusion - which I think is a 1 Tbyte HDD, plus a small amount of SSD - perhaps 100 Gbytes."

So if HD check out OK, then I would upgrade with good RAM as discussed before, if you have to have loads of apps open the go for 32Mb.


Other things to slow down a machine hugely:-

Keep lots of tabs open in the Web Browser you use, some pages will update in the back ground and will also use precious internet bandwidth. Answer - DON'T DO IT!

Leave lots of Emails in Inboxes, I have seen over 100K of emails in several customers mail boxes, so what you ask, the answer is that every time the Email app is opened and in the background for every inbox or opened email folder it will check the header of every email in it with every header on the actual Email server, I think you can easily see this could result in huge amounts of data to and from a machine. It will make the Email app very slow and hog network services massively. Answer - delete unneeded emails and move emails to be kept into other folders. Its down to a user to maintain their data, a computer cannot do it, AI can identify old or unread or duplicates, but it cannot say on email is not needed it is not connected to a users brain.

Any computer operating system will create and leave temporary and old system files knocking around, wasting space and ultimately causing disk fragmentation over time which will slow a machine down eventually, anyone who tells you this is no longer an issue is talking out of their pants. Use a tool like CleanMyMac, it has all sorts of clean up goodies and is easy to use. I have used it for many years because I am lazy.

[dave2010]

Waited until now to test the hard drive - in case it took hours. Disconnected the TM drives, and ran the test. Came back OK in about a minute. So I guess the next step is to order the new memory.

[AJSki2fly]

Waited until now to test the hard drive - in case it took hours. Disconnected the TM drives, and ran the test. Came back OK in about a minute. So I guess the next step is to order the new memory.


Yes, and while waiting tidy up email, web tabs and old files to delete, might want consider Cleanmymac has lots of useful tools

[dave2010]

Yes, and while waiting tidy up email, web tabs and old files to delete, might want consider Cleanmymac has lots of useful toolsIs Cleanmymac safe and reliable? Is it a bit like CCleaner for Windows, which I used to use quite a lot?

[AJSki2fly]

I have used it for at least 7years

[Filterlab]

Don't touch Cleanmymac, Mackeeper or any garbage like that. Waste of time. It's junk ware.

I own Mac Doctor Norwich, been running it for 12 years now. The ONLY cleaner you want is OnyX (completely free). Don't be tempted by any of the rest as they'll simply waste processor cycles and slow the machine down further.

Ditch the horrendous Fusion Drive and get a Mac specialist (like me for example) to upgrade it to an SSD. A SATA SSD will work very well (around 6 times quicker than the Fusion), but even better is a PCIe SSD which replaces the small internal SSD (around 15 times quicker than the Fusion).

Don't attempt to upgrade it yourself. There's a real knack to getting the fragile displays off the chassis, and a slight glass breakage will cost you hundreds in a replacement display.

The RAM upgrade will help a bit, but nothing like it used to. The slowest link in the chain is that rotary drive.

[dave2010]

Finally got round to buying and installing some new memory. I'm not sure whether I've done the right thing - or not.

Looking back upstream it seems I might have thought of replacing the 2 x 4 Gbyte modules with 4 x 8 Gbyte modules.

Looking at this page, it would appear that there are a few possible options - https://uk.crucial.com/compatible-upgrade-for/apple/imac-(retina-5k--27-inch--2019)-imac-19-1

A. Remove the 2 x 4 Gbyte modules - insert 4 x 8 Gbyte modules - total cost about £81.

B. Remove the 2 x 4 Gbyte modules - insert 2 x 16 Gbyte modules - total cost around £84.

C. Simply add in 2 x 16 Gbyte modules - total cost about £56.

As far as I can see there isn't any obvious reason why option C shouldn't work - though this brings the memory total up to 40 Gbytes.

I looked at a few YT videos about upgrading.

In particular this one suggests that the 2019 iMac can actually be upgraded to 128 Gbytes - https://youtu.be/WK0Oyt5JCOg

So what I actually did was option C, which brings the total memory up to 40 Gbytes. Having done this, the system does indeed report that the machine has 40 Gbytes of memory.

That configuration is for the machine I'm typing on now.

I have wondered whether I did the right thing - whether there could be any conflicts between the original 2 x 4 Gbytes memory, and the newly inserted memory, which would slow the machine down.
So yesterday I had a rather protracted online chat with someone from Crucial who seemed to suggest that I had indeed "done it wrong", citing the "fact" that the 3 GHz processor can only manage 32 Gbytes of memory.
He was insistent on that, and I was equally insistent that I was actually chatting to him using the machine reporting 40 Gbytes of memory.

I'm still not quite sure on this. I can say that the machine works. Whether it would work faster if I took out the original 2 x 4 Gbytes of memory I don't know. I don't particularly want to go down the route which the Crucial guy was suggesting of 4 x 8Gbytes of memory - there seems to be no reason to do that - just take out the 2 x 4 Gbytes cards to see if things change, but then again - if things are actually working, then why bother.

Regarding CleanMyMac - which has been discussed above, I eventually bought a copy, and it seems quite good and fairly benign.
I eventually nailed - at least partially - some of the problems with the machine, which turned out to be due to large amounts of email data.
In the past I always used Apple's email client for email, but in the last year or so I found that using the online web browser interface to gmail was sometimes - indeed quite often - better. I also found that when I hit the limit of mail which Google/Gmail will store for me without charge, that I could reduce the email by careful deletion, to keep things functioning, but only just. The problem kept coming back every few weeks. During the pandemic I subscribed to a lot of sites, such as the Washington Post, New York Times etc. also the Telegraph - partly out of boredom - and during the pandemic I wanted to know what was going on. The problem with newspaper sites is that they send out the data whether you want to read it or not. This can generate huge amounts of data which fill up one's inbox, and can also take up a lot of space if the mail client is open on the local computer. I finally found ways to manage the email which seem to work well enough. The obvious way is to search one's email inbox for large attachments - but I'd already tried that. It's modestly successful until it fails. The next thing is to look for sites which send out frequent "updates" - often travel firms, or clothing firms etc. Those senders send out files so frequently that even though the messages are quite small, the total space used is quite large. I'd already spotted that problem a few years ago, with one financial site.

So the solution is to look for email messages - and delete them. Yes - but not quite. If we take the example of the New York Times emails, then one can search for emails which have "New York Times" as search terms, but unfortunately that will discover many hits, as the individual words are quite likely to occur in many messages. This doesn't make the deletion problem easier, as maybe one doesn't want to delete every email like that.

Then I noticed something else. There are some subscription sites which send out a lot of emails, but apparently from different "people". Campaign sites may do that, and there are some music sites which do that too. So what one actually has to do is to locate the actual email sites which are sending out the extra or unwanted emails. Also, some sites re reputable, and at least when one has identified them, it's possible to unsubscribe from future messages. Some sites seem less reputable, and will continue to send messages even if "unsubscribed". So far the solution for those - not guaranteed to work 100% - is to report those as spam. So finally, by adopting a more determined approach to email, I have managed to get the email barrage from so many sites more or less under control. I have done this moderately effectively, so that one day I removed around 1 Gbyte of unwanted email. It's much quicker to let it mount up, then spend an hour or so doing a systematic clear out. Other people might simply pay Google/Gmail for extra storage - which isn't too expensive, but I didn't want to do that as I figured it still wouldn't solve the problem of having too much email I didn't want to keep.

[AJSki2fly]

The Crucial tech guy is right, it will only see the first 32gb of ram of addressable storage. The problem is as I understand it is that the 32gb will now be split over 3 memory slots. This I believe can impact processing efficiency. I believe it is always recommended to use matched pairs of ram, and keep the the same in four slots. So 4 4gb or 4 8gb and so on until you reach the max the machine can take.


Sent from my iPhone using Tapatalk

[struth]

a google account should give you 15gig of free storage which ive never got close to. i delete emails although how big their footprint is i dont know. same the pics i no longer require.

[dave2010]

The Crucial tech guy is right, it will only see the first 32gb of ram of addressable storage. The problem is as I understand it is that the 32gb will now be split over 3 memory slots. This I believe can impact processing efficiency. I believe it is always recommended to use matched pairs of ram, and keep the the same in four slots. So 4 4gb or 4 8gb and so on until you reach the max the machine can take.


Sent from my iPhone using TapatalkIn that case surely just taking out the original 2 x 4 Gbytes should work, as presumably each slot is OK with 16 Gbytes of RAM.

It's odd that it reports having 40 Gbytes though.

I'm not in a desperate hurry to take the back off again, and the machine does seem to be working.
I guess I might have to try again, to see if the speed does go up with 4 x 8Gbytes, instead, or maybe just settle for 16 Gbytes and buy 2 x 4Gbytes additionally.

However I'm really not in a hurry - things seem to be working even if they shouldn't.

[dave2010]

I dug in a little further. My CPU has 6 cores - according to the About My Mac info.

So I looked up addressing for i5 chips. First I did indeed find this page:

https://ark.intel.com/content/www/us/en/ark/products/93337/intel-core-i56585r-processor-6m-cache-up-to-3-60-ghz.html

This does show a limit of 32 Gbytes, but it only has 4 cores. Also, if you look carefully, the processor type was first released in 2016.
Those processors are also described as 6th Generation i5 devices.

So then I looked for later generation i5s, and found this - which is a 9th generation series

https://ark.intel.com/content/www/us/en/ark/products/134898/intel-core-i59400-processor-9m-cache-up-to-4-10-ghz.html

These were released during 2019 - some in different quarters. From this page inspecting the different 6 core processors shows that they can handle up to 128 Gbytes of memory.
Interestingly, this is also true of the 4 core processors issued in that range. OK - the processors are shown as faster than 3 GHz, but Apple may have put them in as they became available.
It's probably cheaper for a manufacturer to put in newer chips as they become available - rather than keeping stocks of older ones. They don't have to tell all the consumers, as long as the final products are in or exceed the base specification.

So on balance I'm guessing that Apple did indeed put 9th generation processors into some of the 2019 models. I guess at this point I don't need to worry about this any more.

As I already mentioned, the machine does seem to be working OK - and I'm typing on it now. I would like it to be faster, but I would expect that if there were a serious mismatch of memory to processor, something would not function.

I don't know if it's possible to identify the exact processor type to nail this down further without looking at the physical chip. Maybe it's possible to do it with a software tool, but I don't know which one that might be - or indeed if there is one.

[AJSki2fly]

I dug in a little further. My CPU has 6 cores - according to the About My Mac info.


As I already mentioned, the machine does seem to be working OK - and I'm typing on it now. I would like it to be faster, but I would expect that if there were a serious mismatch of memory to processor, something would not function.

I don't know if it's possible to identify the exact processor type to nail this down further without looking at the physical chip. Maybe it's possible to do it with a software tool, but I don't know which one that might be - or indeed if there is one.

I am not sure if you iMac is an i5 2019 or i9 2019 machine as in the thread you refer to i9 chip upgrade and later i5.

Assuming it is an i5 processor, as you discuss it at length, which is more common.

I would suggest you have a read of this https://forums.macrumors.com/threads/memory-upgrade-compatibility-list-for-imac-2019-2020.2248911/ especially the "rules of thumb"

also a good source of info on i5 iMacs https://everymac.com/systems/by_processor/intel-core-i5-macs.html

If you click on the Apple logo on your machine and then 'about this Mac' and then 'System Report' you can see all the hardware details, Hardware gives you Machine specifics including Total Number of Cores. If your 27' iMac was built between
Introduction Date: March 19, 2019 Discontinued Date: April 20, 2021 then it will be i5 chip with 6 cores

There are 4 variants all with using the intel 14-nm "Coffee Lake" chipset, it appears only the 3.7 GHz Core i5 (I5-9600K) iMac has features a "9th Generation", so you should be able to determine what yours is from the System Report where it show Processor Speed.

Whatever it is I would still recommend using matched pairs of RAM, as an Apple Genius for 10 years that repaired these machines I and my colleagues would only recommend that and generally Crucial RAM which was reliable. So when upgrading we would not recommend mixing it up.

Hope this helps and does not confused matters more.

[dave2010]

Sorry if somewhere I typed i9 instead of i5. It appears that the machine is an i5 with 6 cores. I haven't been able to drill down further to find the processor number, but does appear that some of the i5 processors were 6 core machines. I ran Cinebench, and the results do indeed suggest 6 cores are what this one has. I do wonder if there's a tool to identify the particular processor, since the Intel site shows several variants around 2019-2020. Whether there are going to be any problems with the machine as it is I can't really say. I'm not sure about balancing up the memory modules - what difference does that make?

I am looking at other problems which I think are software related, so I'll probably stick with things as they are for the moment, unless you tell me more about issues of unbalanced modules, in which case I may make changes. I don't want to spend a lot more chasing up problems which may not really exist.

I reckon I could get a 50% speed improvement by buying a newer machine - though now I'll wait until we hear what the next ranges from Apple will be, plus also pricing etc. Many of the newer machines seem to have a "no upgrade" specification, so that getting an inappropriate spec at purchase time doesn't permit any later upgrade. Buying a new machine with more memory, more of everything is a much more expensive way to go than buying a machine which can later be upgraded.

Thanks for following this one, though.

[struth]

might give you an idea on it...

https://www.makeuseof.com/tag/myths-misconceptions-about-ram/

[AJSki2fly]

Sorry if somewhere I typed i9 instead of i5. It appears that the machine is an i5 with 6 cores. I haven't been able to drill down further to find the processor number, but does appear that some of the i5 processors were 6 core machines. I ran Cinebench, and the results do indeed suggest 6 cores are what this one has. I do wonder if there's a tool to identify the particular processor, since the Intel site shows several variants around 2019-2020. Whether there are going to be any problems with the machine as it is I can't really say. I'm not sure about balancing up the memory modules - what difference does that make?

I am looking at other problems which I think are software related, so I'll probably stick with things as they are for the moment, unless you tell me more about issues of unbalanced modules, in which case I may make changes. I don't want to spend a lot more chasing up problems which may not really exist.

I reckon I could get a 50% speed improvement by buying a newer machine - though now I'll wait until we hear what the next ranges from Apple will be, plus also pricing etc. Many of the newer machines seem to have a "no upgrade" specification, so that getting an inappropriate spec at purchase time doesn't permit any later upgrade. Buying a new machine with more memory, more of everything is a much more expensive way to go than buying a machine which can later be upgraded.

Thanks for following this one, though.

Dave referring to the link Grant posted for you"-

"mixing and matching RAM modules isn't the best for system performance.

For the best system performance, it is advisable to use RAM sticks by the same manufacturer, of the same size, and of the same frequency. But there's a simple reason behind why mixing RAM sizes is usually not the best option to maximize system performance. This is because RAM has several components that all come together to make it perform well.

Match Your RAM for the Best Performance

RAM works best when paired with matching hardware. For optimal performance, your RAM should use the same voltage, and their respective controllers should play well with each other and the motherboard. That's why it's best to use the same RAM model in all slots."

So if you purchased 16GB RAM which has the same frequency(hz) and voltage needs as the original Apple supplied RAM that is still in the iMac then the impact will be minimal. If you have different frequency RAM then all will run at the lowest Hz. If they are not the same then the answer is IMHO to remove the Apple RAM and leave the two 16GB RAM in the first two slots.

With respect to the new 24' iMacs they have the M1 processor and can have 8 or 16GB RAM, and you can choose SSD drive size. The M1 processors are architecturally rather different to Intel and are I believe much more efficient and faster. For general home use any one of these iMacs would far exceed what most people will throw at them. You might push one to its limits if you used it to process music using a professional recording studio package, or were doing professional video editing. So if you opt for one of these pick one with a big enough drive that is double you existing data on you current unit, I would opt for a 16GB ram unit, and off you go and forget it for 7-10 years. (make sure you had a back up hard drive at least twice the size of the new iMac). As to getting a 50% improvement, I would look at specific speed test run on you machine and on a newer spec iMac to get a true comparison.

By the way with any machine if you open lots and lots of applications, have many, many tabs open in Safari or another browser, have masses of Emails in your open Inbox you are likely to choke it and slow the thing down. Also the more web/internet based apps running at the same time will impact efficiency as you will cause a localised network issues trying to support them(bandwidth bottleneck unless on a very high speed service), obviously it will also be impacted by other users on the network as well. In my personal experience at Apple over 10 years, most people would over specify machines for what they actually needed or were going to use it for, in general it was due to bad machine and application management by the user and they thought that bigger and faster would make it better, unfortunately bigger and faster is not always the answer.

[struth]

yeah its inclined to settle for the lowest common denominator.. ive always replayed all slots with same

[dave2010]

Thanks both. I may try removing the Apple original memory to see if that speeds things up. I'm not looking for miracles - just something better than before. I think the M2 or later offerings are going to be much more interesting, but I'll at least wait until after the next Apple conference.

I reckon 32 Gbytes is probably enough for most of what I want to do - but yes - I do run software with potentially heavy loads. Music programs with multiple soft synths, and may have other programs also loaded at the same time - photo editing, video editing etc.

Looking at the Geekbench results suggests that I should be able to get around twice the speed with something like an M2 based Mac Mini - or whatever comes next.

One of my friends seems to have a Mac Studio - but if I go that way I figure I'll be spending £3k and upwards.