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RAM advice - 27" iMac

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  RAM advice  - 27" iMac Another John <lalaw44@hotmail.com> - 2025-10-29 12:02 +0000
    Re: RAM advice  - 27" iMac Tyrone <none@none.none> - 2025-10-29 15:28 +0000
      Re: RAM advice - 27" iMac "David B." <BD@hotmail.co.uk> - 2025-10-29 18:24 +0000
    Re: RAM advice  - 27" iMac Theo <theom+news@chiark.greenend.org.uk> - 2025-10-29 17:40 +0000
      Re: RAM advice  - 27" iMac Theo <theom+news@chiark.greenend.org.uk> - 2025-10-29 18:01 +0000
    Re: RAM advice  - 27" iMac RJH <patchmoney@gmx.com> - 2025-10-30 00:47 +0000
      Re: RAM advice  - 27" iMac Tyrone <none@none.none> - 2025-10-30 00:55 +0000
        Re: RAM advice - 27" iMac Alan B <alanrichardbarker@gmail.com.invalid> - 2025-10-30 06:20 +0000
          Re: RAM advice - 27" iMac RJH <patchmoney@gmx.com> - 2025-10-30 07:08 +0000
          Re: RAM advice - 27" iMac Jaimie Vandenbergh <jaimie@usually.sessile.org> - 2025-10-30 09:25 +0000
            Re: RAM advice - 27" iMac Alan B <alanrichardbarker@gmail.com.invalid> - 2025-10-30 09:34 +0000
            Re: RAM advice - 27" iMac "David B." <BD@hotmail.co.uk> - 2025-10-30 11:04 +0000
            Re: RAM advice - 27" iMac Alan B <alanrichardbarker@gmail.com.invalid> - 2025-10-30 11:33 +0000
            Re: RAM advice - 27" iMac Mark <captain.black@gmail.com> - 2025-10-30 16:39 +0000
            Re: RAM advice - 27" iMac Another John <lalaw44@hotmail.com> - 2025-10-31 16:14 +0000
              Re: RAM advice - 27" iMac Theo <theom+news@chiark.greenend.org.uk> - 2025-10-31 16:37 +0000
              Re: RAM advice - 27" iMac "David B." <BDonBlockNews@invalid.invalid> - 2025-10-31 16:37 +0000
    Re: RAM advice  - 27" iMac Jaimie Vandenbergh <jaimie@usually.sessile.org> - 2025-10-30 09:22 +0000
      Re: RAM advice - 27" iMac "David B." <BD@hotmail.co.uk> - 2025-10-30 11:02 +0000
      Re: RAM advice  - 27" iMac Another John <lalaw44@hotmail.com> - 2025-11-13 14:59 +0000

#182167 — RAM advice - 27" iMac

Hello all

I have a 27" Retina iMac, year 2019.   Quite often, seems to be struggling:
spinning rainbow disc, slight hesitations in doing things, etc.

I think it may be that Sequoia (15.6.1) is too 'heavy' for it - ???   I only
have 8GB RAM installed - 2x4GB DIMMs.
(My "other" 27" has 16GB, but that's vintage 2013, and I understand that that
RAM won't go into the 2019 one).  

I am thinking I ought to boost the RAM in the 2019 one. I've been led to
believe (by various discussions I found) that I should upgrade the RAM with
the same DIMMs as are already installed -- so I think my max upgrade will be
to 16GB (two more 4GB DIMMs).  [unless I go mad and buy, e.g. four 8GB DIMMs -
which would be beyond my budget.].

Aside: briefly scanning the DIMM suppliers, it seems that 4GB DIMMs are now
quite hard to come by!

Do you have any opinions about any of the above? If so, thanks in
anticipation,

Another John

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#182170

On Oct 29, 2025 at 8:02:51 AM EDT, "Another John" <lalaw44@hotmail.com> wrote:

> Hello all
> 
> I have a 27" Retina iMac, year 2019.   Quite often, seems to be struggling:
> spinning rainbow disc, slight hesitations in doing things, etc.
> 
> I think it may be that Sequoia (15.6.1) is too 'heavy' for it - ???   I only
> have 8GB RAM installed - 2x4GB DIMMs.
> (My "other" 27" has 16GB, but that's vintage 2013, and I understand that that
> RAM won't go into the 2019 one).
> 
> I am thinking I ought to boost the RAM in the 2019 one. I've been led to
> believe (by various discussions I found) that I should upgrade the RAM with
> the same DIMMs as are already installed -- so I think my max upgrade will be
> to 16GB (two more 4GB DIMMs).  [unless I go mad and buy, e.g. four 8GB DIMMs -
> which would be beyond my budget.].
> 
> Aside: briefly scanning the DIMM suppliers, it seems that 4GB DIMMs are now
> quite hard to come by!
> 
> Do you have any opinions about any of the above? If so, thanks in
> anticipation,

The RAM specs for your iMac are here:

<https://support.apple.com/en-us/108317>

RAM sticks are typically installed in pairs. This has 4 slots and as you noted
4GB DIMMS are hard to find these days. So you could get two 8GB SO-DIMMS and
keep your existing two 4GB SO-DIMMS and have 24GB total. 

BTW this model can take up to 64GB total, 4 x 16GB.

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#182173 — Re: RAM advice - 27" iMac

On 29/10/2025 15:28, Tyrone wrote:
> On Oct 29, 2025 at 8:02:51 AM EDT, "Another John" <lalaw44@hotmail.com> wrote:
> 
>> Hello all
>>
>> I have a 27" Retina iMac, year 2019.   Quite often, seems to be struggling:
>> spinning rainbow disc, slight hesitations in doing things, etc.
>>
>> I think it may be that Sequoia (15.6.1) is too 'heavy' for it - ???   I only
>> have 8GB RAM installed - 2x4GB DIMMs.
>> (My "other" 27" has 16GB, but that's vintage 2013, and I understand that that
>> RAM won't go into the 2019 one).
>>
>> I am thinking I ought to boost the RAM in the 2019 one. I've been led to
>> believe (by various discussions I found) that I should upgrade the RAM with
>> the same DIMMs as are already installed -- so I think my max upgrade will be
>> to 16GB (two more 4GB DIMMs).  [unless I go mad and buy, e.g. four 8GB DIMMs -
>> which would be beyond my budget.].
>>
>> Aside: briefly scanning the DIMM suppliers, it seems that 4GB DIMMs are now
>> quite hard to come by!
>>
>> Do you have any opinions about any of the above? If so, thanks in
>> anticipation,
> 
> The RAM specs for your iMac are here:
> 
> <https://support.apple.com/en-us/108317>
> 
> RAM sticks are typically installed in pairs. This has 4 slots and as you noted
> 4GB DIMMS are hard to find these days. So you could get two 8GB SO-DIMMS and
> keep your existing two 4GB SO-DIMMS and have 24GB total.
> 
> BTW this model can take up to 64GB total, 4 x 16GB.

What you say is 100% correct.

It is exactly how I upgraded *MY* 27 inch iMac! 🙂

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#182171

Another John <lalaw44@hotmail.com> wrote:
> Hello all
> 
> I have a 27" Retina iMac, year 2019.   Quite often, seems to be struggling:
> spinning rainbow disc, slight hesitations in doing things, etc.
> 
> I think it may be that Sequoia (15.6.1) is too 'heavy' for it - ???   I only
> have 8GB RAM installed - 2x4GB DIMMs.
> (My "other" 27" has 16GB, but that's vintage 2013, and I understand that that
> RAM won't go into the 2019 one).  
> 
> I am thinking I ought to boost the RAM in the 2019 one. I've been led to
> believe (by various discussions I found) that I should upgrade the RAM with
> the same DIMMs as are already installed -- so I think my max upgrade will be
> to 16GB (two more 4GB DIMMs).  [unless I go mad and buy, e.g. four 8GB DIMMs -
> which would be beyond my budget.].
> 
> Aside: briefly scanning the DIMM suppliers, it seems that 4GB DIMMs are now
> quite hard to come by!
> 
> Do you have any opinions about any of the above? If so, thanks in
> anticipation,

I'm not sure the specifics of matching what you have, but you should be able
to remove them and fit new DIMMs. eg Crucial has a memory selector:
https://www.crucial.com/compatible-upgrade-for/apple/imac-(retina-5k--27-inch--2019)-imac-19-1
(it quotes prices in dollars, but if you search for the part numbers you
should be able to find UK suppliers)

If there are 4 slots you should be able to fit either two or four matching
DIMMs.  eg you could go for 2x8GB or 2x16GB rather than 4x4GB.

It's possible fitting two pairs of mismatched DIMMs may work - DDR4 isn't as
fussy as DDR5 - so if you have spare DIMMs available you could just try them and
see.  eg if you did buy 2x8 you could try adding your existing 2x4 and see
if you got 24GB.

Theo

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#182172

Theo <theom+news@chiark.greenend.org.uk> wrote:
> I'm not sure the specifics of matching what you have, but you should be able
> to remove them and fit new DIMMs. eg Crucial has a memory selector:
> https://www.crucial.com/compatible-upgrade-for/apple/imac-(retina-5k--27-inch--2019)-imac-19-1
> (it quotes prices in dollars, but if you search for the part numbers you
> should be able to find UK suppliers)
> 
> If there are 4 slots you should be able to fit either two or four matching
> DIMMs.  eg you could go for 2x8GB or 2x16GB rather than 4x4GB.
> 
> It's possible fitting two pairs of mismatched DIMMs may work - DDR4 isn't as
> fussy as DDR5 - so if you have spare DIMMs available you could just try them and
> see.  eg if you did buy 2x8 you could try adding your existing 2x4 and see
> if you got 24GB.

By the way, while there are memory modules specifically labelled as 'for
Mac' you may get lucky using modules that aren't.  You want DDR4 SODIMMs
which aren't ECC (most aren't), and if you search Amazon there are many - a
16GB kit is about £50.  If you buy somewhere with an easy returns policy you
should be able to try them and see if they work.

A single DIMM may also work, with a slight reduction in speed.  When you fit
them, typically there is an order the slots should be populated in - check
you have filled up in order from the first slot.

Theo

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#182175

On 29 Oct 2025 at 12:02:51 GMT, Another John wrote:

> Hello all
> 
> I have a 27" Retina iMac, year 2019.   Quite often, seems to be struggling:
> spinning rainbow disc, slight hesitations in doing things, etc.
> 
> I think it may be that Sequoia (15.6.1) is too 'heavy' for it - ???   I only
> have 8GB RAM installed - 2x4GB DIMMs.
> (My "other" 27" has 16GB, but that's vintage 2013, and I understand that that
> RAM won't go into the 2019 one).
> 
> I am thinking I ought to boost the RAM in the 2019 one. I've been led to
> believe (by various discussions I found) that I should upgrade the RAM with
> the same DIMMs as are already installed -- so I think my max upgrade will be
> to 16GB (two more 4GB DIMMs).  [unless I go mad and buy, e.g. four 8GB DIMMs -
> which would be beyond my budget.].
> 
> Aside: briefly scanning the DIMM suppliers, it seems that 4GB DIMMs are now
> quite hard to come by!
> 
> Do you have any opinions about any of the above? If so, thanks in
> anticipation,
> 

You could just bump up what's there with 2 x 8GB - about £30 - and if the
existing 8GB works with whatever you buy, so much the better. I've likely got
some knocking about - by all means drop me an email for what will be 'most
advantageous pricing'.

I think the bottleneck in those iMacs is likely the Fusion hard disk, though.
I'd run some utilities to see if it's working as it should. But I don't think
they were ever that speedy. Replacing with an SSD would speed things up.
-- 
Cheers, Rob, Sheffield UK

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#182176

On Oct 29, 2025 at 8:47:06 PM EDT, "RJH" <patchmoney@gmx.com> wrote:

> On 29 Oct 2025 at 12:02:51 GMT, Another John wrote:
> 
>> Hello all
>> 
>> I have a 27" Retina iMac, year 2019.   Quite often, seems to be struggling:
>> spinning rainbow disc, slight hesitations in doing things, etc.
>> 
>> I think it may be that Sequoia (15.6.1) is too 'heavy' for it - ???   I only
>> have 8GB RAM installed - 2x4GB DIMMs.
>> (My "other" 27" has 16GB, but that's vintage 2013, and I understand that that
>> RAM won't go into the 2019 one).
>> 
>> I am thinking I ought to boost the RAM in the 2019 one. I've been led to
>> believe (by various discussions I found) that I should upgrade the RAM with
>> the same DIMMs as are already installed -- so I think my max upgrade will be
>> to 16GB (two more 4GB DIMMs).  [unless I go mad and buy, e.g. four 8GB DIMMs -
>> which would be beyond my budget.].
>> 
>> Aside: briefly scanning the DIMM suppliers, it seems that 4GB DIMMs are now
>> quite hard to come by!
>> 
>> Do you have any opinions about any of the above? If so, thanks in
>> anticipation,
>> 
> 
> You could just bump up what's there with 2 x 8GB - about £30 - and if the
> existing 8GB works with whatever you buy, so much the better. I've likely got
> some knocking about - by all means drop me an email for what will be 'most
> advantageous pricing'.
> 
> I think the bottleneck in those iMacs is likely the Fusion hard disk, though.
> I'd run some utilities to see if it's working as it should. But I don't think
> they were ever that speedy. Replacing with an SSD would speed things up.

Absolutely.  Replacing a spinning disk with an SSD is the best upgrade ever
for older PCs.

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#182177 — Re: RAM advice - 27" iMac

Tyrone <none@none.none> wrote:
> On Oct 29, 2025 at 8:47:06 PM EDT, "RJH" <patchmoney@gmx.com> wrote:
> 
>> On 29 Oct 2025 at 12:02:51 GMT, Another John wrote:
>> 
>>> Hello all
>>> 
>>> I have a 27" Retina iMac, year 2019.   Quite often, seems to be struggling:
>>> spinning rainbow disc, slight hesitations in doing things, etc.
>>> 
>>> I think it may be that Sequoia (15.6.1) is too 'heavy' for it - ???   I only
>>> have 8GB RAM installed - 2x4GB DIMMs.
>>> (My "other" 27" has 16GB, but that's vintage 2013, and I understand that that
>>> RAM won't go into the 2019 one).
>>> 
>>> I am thinking I ought to boost the RAM in the 2019 one. I've been led to
>>> believe (by various discussions I found) that I should upgrade the RAM with
>>> the same DIMMs as are already installed -- so I think my max upgrade will be
>>> to 16GB (two more 4GB DIMMs).  [unless I go mad and buy, e.g. four 8GB DIMMs -
>>> which would be beyond my budget.].
>>> 
>>> Aside: briefly scanning the DIMM suppliers, it seems that 4GB DIMMs are now
>>> quite hard to come by!
>>> 
>>> Do you have any opinions about any of the above? If so, thanks in
>>> anticipation,
>>> 
>> 
>> You could just bump up what's there with 2 x 8GB - about £30 - and if the
>> existing 8GB works with whatever you buy, so much the better. I've likely got
>> some knocking about - by all means drop me an email for what will be 'most
>> advantageous pricing'.
>> 
>> I think the bottleneck in those iMacs is likely the Fusion hard disk, though.
>> I'd run some utilities to see if it's working as it should. But I don't think
>> they were ever that speedy. Replacing with an SSD would speed things up.
> 
> Absolutely.  Replacing a spinning disk with an SSD is the best upgrade ever
> for older PCs.

How easy is that? A compromise might be to purchase a USB SSD and clone the
system to that using say CCC or SuperDuper and configure it as the boot
drive.

-- 
Cheers, Alan

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#182178 — Re: RAM advice - 27" iMac

On 30 Oct 2025 at 06:20:41 GMT, Alan B wrote:

> Tyrone <none@none.none> wrote:
>> On Oct 29, 2025 at 8:47:06 PM EDT, "RJH" <patchmoney@gmx.com> wrote:
>> 
>>> On 29 Oct 2025 at 12:02:51 GMT, Another John wrote:
>>> 
>>>> Hello all
>>>> 
>>>> I have a 27" Retina iMac, year 2019.   Quite often, seems to be struggling:
>>>> spinning rainbow disc, slight hesitations in doing things, etc.
>>>> 
>>>> I think it may be that Sequoia (15.6.1) is too 'heavy' for it - ???   I only
>>>> have 8GB RAM installed - 2x4GB DIMMs.
>>>> (My "other" 27" has 16GB, but that's vintage 2013, and I understand that that
>>>> RAM won't go into the 2019 one).
>>>> 
>>>> I am thinking I ought to boost the RAM in the 2019 one. I've been led to
>>>> believe (by various discussions I found) that I should upgrade the RAM with
>>>> the same DIMMs as are already installed -- so I think my max upgrade will be
>>>> to 16GB (two more 4GB DIMMs).  [unless I go mad and buy, e.g. four 8GB DIMMs -
>>>> which would be beyond my budget.].
>>>> 
>>>> Aside: briefly scanning the DIMM suppliers, it seems that 4GB DIMMs are now
>>>> quite hard to come by!
>>>> 
>>>> Do you have any opinions about any of the above? If so, thanks in
>>>> anticipation,
>>>> 
>>> 
>>> You could just bump up what's there with 2 x 8GB - about £30 - and if the
>>> existing 8GB works with whatever you buy, so much the better. I've likely got
>>> some knocking about - by all means drop me an email for what will be 'most
>>> advantageous pricing'.
>>> 
>>> I think the bottleneck in those iMacs is likely the Fusion hard disk, though.
>>> I'd run some utilities to see if it's working as it should. But I don't think
>>> they were ever that speedy. Replacing with an SSD would speed things up.
>> 
>> Absolutely.  Replacing a spinning disk with an SSD is the best upgrade ever
>> for older PCs.
> 
> How easy is that?

Not that easy, involving breaking the glue of the screen.

> A compromise might be to purchase a USB SSD and clone the
> system to that using say CCC or SuperDuper and configure it as the boot
> drive.

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#182181 — Re: RAM advice - 27" iMac

On 30 Oct 2025 at 06:20:41 GMT, "Alan B"
<alanrichardbarker@gmail.com.invalid> wrote:

> Tyrone <none@none.none> wrote:
>> On Oct 29, 2025 at 8:47:06 PM EDT, "RJH" <patchmoney@gmx.com> wrote:
>> 
>> Absolutely.  Replacing a spinning disk with an SSD is the best upgrade ever
>> for older PCs.
> 
> How easy is that? A compromise might be to purchase a USB SSD and clone the
> system to that using say CCC or SuperDuper and configure it as the boot
> drive.

Hard. Delicate work and the screen glass is easily shattered (guess how
I know).

Since it's an Intel desktop you can just get a fast USB3/TB3 external
SSD and whack it in the back, clone and boot off it. No fuss about 'only
boot from internal' like the Mseries do.

Does yours actually have a spinning disk in? 2019's I thought were SSD
first and only have spinners as an option, but it's a while ago and I've
barely thought about Intel Macs since going M1 in 2020 :)

    Cheers - Jaimie
-- 
I love children, especially when they cry, for then someone takes them away.
                                                           -- Nancy Mitford

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#182182 — Re: RAM advice - 27" iMac

On 30 Oct 2025 at 09:25:19 GMT, "Jaimie Vandenbergh"
<jaimie@usually.sessile.org> wrote:

> On 30 Oct 2025 at 06:20:41 GMT, "Alan B"
> <alanrichardbarker@gmail.com.invalid> wrote:
> 
>> Tyrone <none@none.none> wrote:
>>> On Oct 29, 2025 at 8:47:06 PM EDT, "RJH" <patchmoney@gmx.com> wrote:
>>> 
>>> Absolutely.  Replacing a spinning disk with an SSD is the best upgrade ever
>>> for older PCs.
>> 
>> How easy is that? A compromise might be to purchase a USB SSD and clone the
>> system to that using say CCC or SuperDuper and configure it as the boot
>> drive.
> 
> Hard. Delicate work and the screen glass is easily shattered (guess how
> I know).

Oh dear!

> Since it's an Intel desktop you can just get a fast USB3/TB3 external
> SSD and whack it in the back, clone and boot off it. No fuss about 'only
> boot from internal' like the Mseries do.
> 
> Does yours actually have a spinning disk in? 2019's

You mean AJ's  - my only iMac was a Strawberry  G3 way back.

-- 
Cheers, Alan

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#182184 — Re: RAM advice - 27" iMac

On 30/10/2025 09:25, Jaimie Vandenbergh wrote:
> On 30 Oct 2025 at 06:20:41 GMT, "Alan B"
> <alanrichardbarker@gmail.com.invalid> wrote:
> 
>> Tyrone <none@none.none> wrote:
>>> On Oct 29, 2025 at 8:47:06 PM EDT, "RJH" <patchmoney@gmx.com> wrote:
>>>
>>> Absolutely.  Replacing a spinning disk with an SSD is the best upgrade ever
>>> for older PCs.
>>
>> How easy is that? A compromise might be to purchase a USB SSD and clone the
>> system to that using say CCC or SuperDuper and configure it as the boot
>> drive.
> 
> Hard. Delicate work and the screen glass is easily shattered (guess how
> I know).

Oops!
> Since it's an Intel desktop you can just get a fast USB3/TB3 external
> SSD and whack it in the back, clone and boot off it. No fuss about 'only
> boot from internal' like the Mseries do.

That is exactly what I have done on the iMac from which I am sending 
this message! The SSD part of my Fusion drive failed. (2017)
> Does yours actually have a spinning disk in? 2019's I thought were SSD
> first and only have spinners as an option, but it's a while ago and I've
> barely thought about Intel Macs since going M1 in 2020 :)
> 
>      Cheers - Jaimie

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#182185 — Re: RAM advice - 27" iMac

On 2025-10-30, Jaimie Vandenbergh <jaimie@usually.sessile.org> wrote:
> On 30 Oct 2025 at 06:20:41 GMT, "Alan B"
><alanrichardbarker@gmail.com.invalid> wrote:
>
>> Tyrone <none@none.none> wrote:
>>> On Oct 29, 2025 at 8:47:06 PM EDT, "RJH" <patchmoney@gmx.com> wrote:
>>> 
>>> Absolutely.  Replacing a spinning disk with an SSD is the best upgrade ever
>>> for older PCs.
>> 
>> How easy is that? A compromise might be to purchase a USB SSD and clone the
>> system to that using say CCC or SuperDuper and configure it as the boot
>> drive.
>
> Hard. Delicate work and the screen glass is easily shattered (guess how
> I know).
>
> Since it's an Intel desktop you can just get a fast USB3/TB3 external
> SSD and whack it in the back, clone and boot off it. No fuss about 'only
> boot from internal' like the Mseries do.

As I stated earlier I once owned a G3 iMac. I don't think I would buy 
another iMac as with a Mac Mini you can choose a monitor/keyboard/mouse 
etc. that meets your needs. If, say you decide you want a larger monitor, 
you can trade it in for a replacement.

-- 
Cheers, Alan

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#182186 — Re: RAM advice - 27" iMac

On 30 Oct 2025 at 9:25:19 AM GMT, "Jaimie Vandenbergh"
<jaimie@usually.sessile.org> wrote:

> On 30 Oct 2025 at 06:20:41 GMT, "Alan B"
> <alanrichardbarker@gmail.com.invalid> wrote:
> 
>> Tyrone <none@none.none> wrote:
>>> On Oct 29, 2025 at 8:47:06 PM EDT, "RJH" <patchmoney@gmx.com> wrote:
>>> 
>>> Absolutely.  Replacing a spinning disk with an SSD is the best upgrade ever
>>> for older PCs.
>> 
>> How easy is that? A compromise might be to purchase a USB SSD and clone the
>> system to that using say CCC or SuperDuper and configure it as the boot
>> drive.
> 
> Hard. Delicate work and the screen glass is easily shattered (guess how
> I know).
> 
> Since it's an Intel desktop you can just get a fast USB3/TB3 external
> SSD and whack it in the back, clone and boot off it. No fuss about 'only
> boot from internal' like the Mseries do.
> 
> Does yours actually have a spinning disk in? 2019's I thought were SSD
> first and only have spinners as an option, but it's a while ago and I've
> barely thought about Intel Macs since going M1 in 2020 :)
> 
>     Cheers - Jaimie

MacTracker says the 19" was either Fusion or Flash (the 21.5" also had the
option of being SATA).

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#182188 — Re: RAM advice - 27" iMac

On 30 Oct 2025 at 09:25:19 GMT, "Jaimie Vandenbergh"
<jaimie@usually.sessile.org> wrote:

> Does yours actually have a spinning disk in?

(Only the spinning rainbow disc, when I'm waiting for something to happen! :-D
)

I *finally* found how to find out what the actual disk is (System Setting used
to be so much simpler tha it is!!).
I knew it was an SSD, allegedly 1TB, but 849GB according to the Finder &
friends. So: it's "APPLE SSD SM0032L".

Thanks everyone for the discussion on RAM; I'm pursuing this in among too many
other things, hence it's moving slowly.

Thanks in particular to Jaimie, not least because you used the magic word
"Kingston": THAT's where I've bought RAM in the distant past!

I'll be thinking it over: I'm sure that when reading discussions on the web
before posting here, I saw the advice that mixing sizes (e.g. 8s with 4s)
might actually slow things down a bit, rather than put a rocket up the system.
I think it was Apple advice - I have to find it again.

I'm much further forward than I was, so thanks again everyone,

Another John

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#182189 — Re: RAM advice - 27" iMac

Another John <lalaw44@hotmail.com> wrote:
> I'll be thinking it over: I'm sure that when reading discussions on the web
> before posting here, I saw the advice that mixing sizes (e.g. 8s with 4s)
> might actually slow things down a bit, rather than put a rocket up the system.
> I think it was Apple advice - I have to find it again.

RAM comes in different speed grades.  If you mix grades, the system will
operate at the speed of the slowest grade present.  This might cause a
slight slowdown, but only when you are bottlenecked on memory bandwidth
(which is rarely).

If the system is short of RAM, as it sounds like it might be, the system is
going to slow down by either storing data compressed in RAM, or using your
SSD as swap.  This is vastly slower than the slowdown caused by having to
run the memory at a slower speed grade.

To use a dodgy analogy, it's like dropping down from a 1.8 to a 1.6 litre
engine versus walking.

Theo

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#182190 — Re: RAM advice - 27" iMac

On 31/10/2025 16:14, Another John wrote:
> On 30 Oct 2025 at 09:25:19 GMT, "Jaimie Vandenbergh"
> <jaimie@usually.sessile.org> wrote:
> 
>> Does yours actually have a spinning disk in?
> 
> (Only the spinning rainbow disc, when I'm waiting for something to happen! :-D
> )
> 
> I *finally* found how to find out what the actual disk is (System Setting used
> to be so much simpler tha it is!!).
> I knew it was an SSD, allegedly 1TB, but 849GB according to the Finder &
> friends. So: it's "APPLE SSD SM0032L".
> 
> Thanks everyone for the discussion on RAM; I'm pursuing this in among too many
> other things, hence it's moving slowly.
> 
> Thanks in particular to Jaimie, not least because you used the magic word
> "Kingston": THAT's where I've bought RAM in the distant past!
> 
> I'll be thinking it over: I'm sure that when reading discussions on the web
> before posting here, I saw the advice that mixing sizes (e.g. 8s with 4s)
> might actually slow things down a bit, rather than put a rocket up the system.
> I think it was Apple advice - I have to find it again.
> 
> I'm much further forward than I was, so thanks again everyone,
> 
> Another John

You are welcome!

2x4  and  2x8 works just fine for me!

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#182180

On 29 Oct 2025 at 12:02:51 GMT, "Another John" <lalaw44@hotmail.com>
wrote:
> 
> I am thinking I ought to boost the RAM in the 2019 one. I've been led to
> believe (by various discussions I found) that I should upgrade the RAM with
> the same DIMMs as are already installed -- so I think my max upgrade will be
> to 16GB (two more 4GB DIMMs).  [unless I go mad and buy, e.g. four 8GB DIMMs -
> which would be beyond my budget.].

You can pop a pair of 8's in alongside the existing 4's. As to
purchasing the right ones - go to
https://www.kingston.com/unitedkingdom/en/memory/desktop-laptop and
enter "apple imac 2019" and pick yours off the short list. They have
8gig sodimms in stock at the moment, and Kingston will always take
returns if they don't work in your machine.

    Cheers - Jaimie
-- 
The person who says it cannot be done should not interrupt the person doing it.

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#182183 — Re: RAM advice - 27" iMac

On 30/10/2025 09:22, Jaimie Vandenbergh wrote:
> You can pop a pair of 8's in alongside the existing 4's.

That is correct. It is what I did on THIS iMac! ;-)

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#182232

On 30 Oct 2025 at 09:22:11 GMT, "Jaimie Vandenbergh"
<jaimie@usually.sessile.org> wrote:

> On 29 Oct 2025 at 12:02:51 GMT, "Another John" <lalaw44@hotmail.com>
> wrote:
>> 
>> I am thinking I ought to boost the RAM in the 2019 one. I've been led to
>> believe (by various discussions I found) that I should upgrade the RAM with
>> the same DIMMs as are already installed -- so I think my max upgrade will be
>> to 16GB (two more 4GB DIMMs).  [unless I go mad and buy, e.g. four 8GB DIMMs -
>> which would be beyond my budget.].
> 
> You can pop a pair of 8's in alongside the existing 4's. As to
> purchasing the right ones - go to
> https://www.kingston.com/unitedkingdom/en/memory/desktop-laptop and
> enter "apple imac 2019" and pick yours off the short list. They have
> 8gig sodimms in stock at the moment, and Kingston will always take
> returns if they don't work in your machine.
> 
>     Cheers - Jaimie

OK, well I've done that now (finally!). 

Kingston are superb: a great ordering facility, quickly expedited, and
delivered by Fedex (whom I also found very good). 

I now have 24GB (2x8Gbs tucked in with the original 2x4Gbs (alternated, so
that "Channel A" is upgraded like "Channel B" (thanks to Apple themselves for
that info)).  The Apple installtion advice is also superb, and a quick review
of the odd Youtube of the process was reassuring.

I can't say I've noticed a vast leap in speed (but I never make many large
demands), but I am hoping for a slicker performance all round, and above all
I'm hoping I don't see the spinning rainbow again for a good while.

Thanks for all the advice
Another John

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