It's Official: 2019 27" iMac can take 128GB of RAM


aman88

macrumors regular
Mar 21, 2019
110
17
Correct me if I’m wrong... but when I froze the video when they had the “about this iMac” up, it looked like that is the base 27 inch with the i5 and pro 570x which apple lists as only able to go up to 32 gb of ram... that’s crazy...
 

amoergosum

macrumors 6502
Oct 20, 2008
376
42
Correct me if I’m wrong... but when I froze the video when they had the “about this iMac” up, it looked like that is the base 27 inch with the i5 and pro 570x which apple lists as only able to go up to 32 gb of ram... that’s crazy...
...yep.

>>>

 

aman88

macrumors regular
Mar 21, 2019
110
17
Thanks I was watching it on my XR so it was hard to tell... that’s absurd because on apples site it says up to 32 gb... I wonder what type of memory they used...
 

vaugha

macrumors 6502a
Nov 3, 2011
542
165
Did ifixit do a teardown on the new imac yet?

If the ram size can accommodate 128gb then the power consumption will increase commensurately and I'm a little skeptical whether there is enough headroom for future psu capacity degradation. 2017 imacs have 300w psus and apple states i9 5k imac consumes 262w under max cpu load.
 

aman88

macrumors regular
Mar 21, 2019
110
17
I believe the model tested here is the 8th gen i5 which is 65w as compared to 95w of the 9th gens?
 

herobrine

macrumors newbie
Mar 31, 2019
2
0
Did ifixit do a teardown on the new imac yet?

If the ram size can accommodate 128gb then the power consumption will increase commensurately and I'm a little skeptical whether there is enough headroom for future psu capacity degradation. 2017 imacs have 300w psus and apple states i9 5k imac consumes 262w under max cpu load.
Macsales.com lists the 32GB modules with the same 1.2v power consumption as all the other compatible modules—if your mac can run the 4GB module, then it can run the 32GB one. As far as I understand, greater capacity does not necessarily mean more power consumption. I don't think there's anything to worry about in that regard.
 

vaugha

macrumors 6502a
Nov 3, 2011
542
165
Macsales.com lists the 32GB modules with the same 1.2v power consumption as all the other compatible modules—if your mac can run the 4GB module, then it can run the 32GB one. As far as I understand, greater capacity does not necessarily mean more power consumption. I don't think there's anything to worry about in that regard.
So are you saying 128gb of ram will consume the same amount of power as 32gb? Voltage is not a measure of power, but only a measure of electric potential difference. Power is measured in either watts or joules.
 

ferencav

macrumors member
Mar 31, 2019
34
16
This is great news, but why would Apple mention a lower maximum capacity? Somehow it feels not completely secure to put in 128GB. Or am I wrong?
 

velocityg4

macrumors 601
Dec 19, 2004
4,621
1,196
Georgia
So are you saying 128gb of ram will consume the same amount of power as 32gb? Voltage is not a measure of power, but only a measure of electric potential difference. Power is measured in either watts or joules.
Power consumption may differ. Current DDR4 desktop modules typically use about 1.5W per module. The worst case I've read about is 3W per module. The iMac uses laptop modules which would normally use less power. Assuming this isn't true and power draw is as high as desktop modules. The worst case scenario is the iMac with 128GB RAM is using 12W for the RAM rather than 6W at peak load. These numbers are minuscule in comparison to high draw components like the CPU and GPU.

Manufacturers typically give their PSU at least a 25% margin between peak system draw and PSU capacity. An additional 6W on even a top spec iMac won't hurt anything. It's also unlikely someone will run at peak draw outside of synthetic benchmarks. Even with a heavy workload it's rare that any task will be evenly balanced enough to max out a CPU and GPU simultaneously.
 

herobrine

macrumors newbie
Mar 31, 2019
2
0
So are you saying 128gb of ram will consume the same amount of power as 32gb? Voltage is not a measure of power, but only a measure of electric potential difference. Power is measured in either watts or joules.
You know, you're right, I wasn't thinking completely straight when I wrote that, had just woken up. However, the point that denser modules did not necessarily consume more energy still stands. All DDR4 SO-DIMM RAM modules should consume the same amount of energy and if there is more consumed by a 32GB module than an 8GB one, the difference is so negligible it's hardly quantifiable.
 

ferencav

macrumors member
Mar 31, 2019
34
16
So it's safe to use 128 GB with the iMac 2019? My iMac arrives this week and I'd like to buy 64 Gb memory for it. The option to upgrade to 128 Gb in the future is tempting so if it's safe I order 2x32Gb, if it's unclear I go for 4x16Gb.
 
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RyanXM

macrumors 6502
Original poster
Jul 7, 2012
333
352
DFW, TX
So it's safe to use 128 GB with the iMac 2019? My iMac arrives this week and I'd like to buy 64 Gb memory for it. The option to upgrade to 128 Gb in the future is tempting so if it's safe I order 2x32Gb, if it's unclear I go for 4x16Gb.
It is 100% safe to use 128GB. I've been using it for 3 days now and no ill effects from it.
 

macduke

macrumors G4
Jun 27, 2007
10,571
14,064
Central U.S.
I might do this in the late 2020s to keep this machine alive forever if the fans and disk writes hold up and nothing else pops. It won't be my primary machine by then but 32GB RAM modules will probably be dirt cheap so why not? Although I might not be able to find them except used. Sometimes with tech prices go down to a certain point and then go back up somewhat when they become rare.

Part of me wants to do it now to see if I would actually notice a difference but $1100 is $1100. I just want to borrow it to test, lol. In a few years I will probably upgrade my 40GB to 64GB when the 2x16GB modules drop below $100 and that will be plenty. I noticed the 2x16GB Crucial modules I used to upgrade to 40GB have already dropped from $199 to $189 so it might be sooner rather than later, lol.
 

aumu1999

macrumors newbie
Oct 4, 2019
1
0
It was widely reported that my model of iMac would support 128GB 3rd party memory upgrade. I am running the iMac (Retina 5K, 27-inch, 2019) 3.7 GHz Intel Core i5 with Radeon Pro 580X 8 GB. I ordered the 4x 32GB kit from OWC. Upon installing all 4 modules I could not get the iMac to boot up. After calling tech support at the memory retailer they told me to try putting one module in at a time and spacing it out 1 to 2 hours between adding each additional 32GB module. I tried that and was able to get it up to 3x32 for 96GB. Each time I would add the 4th module it would crash and reboot, and act very unstable. I tried different modules. I ordered another kit of 4 32GB modules and tested those additional 4. Each time I tried bringing it up to 128GB it failed the Rember test, and would powercycle itself randomly at 15 or 30 minute intervals, booting back up to an error message. Apple is saying it wont work past 64GB. I have got it up to 96GB and it is stable running intense programs and does not crash. I have tested it with 8 different ram modules and it seems it is not a problem with the slot or any of the modules itself, but rather the system itself does not tolerate 128GB as the memory reseller claims it does. Currently I am out of pocket $1,700 on this memory upgrade and am going to be returning the excess and keeping it at 96GB unless there is a problem. I would not recommend to try 128GB. This is definitely not a configuration that this version of iMac tolerates. Once you start opening programs it will crash and turn off with 128GB installed. If you are just looking at the desktop it may stay online for up to 1 hour but will eventually power itself off.
 

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