iMac 27-Inch "Core i7" 3.5 Late 2013 Max RAM is higher than 32gb

[Thomasmasoniv]

My wife has had a "Late 2013 27in Imac" for 6 years and does print design on it 24/7. It's been getting long in the tooth and I've upgraded it over the years with an SSD and added 32gb of ram a few years ago which it regularly maxes out through Photoshop.

We were debating getting something new but really the only problem with it was the low amount of Ram. Plus this Imac had delivered so well over the years I figured I would experiment.

According to every source available, the 2013 Imac is limited to 32gb of ram. Even Intel lists it's CPU i7 4771 as only taking 32gb.
I figured with the lack of any evidence online of anyone testing that limit, I would give it a try.

I ordered two 16gb DDR3L 1600 Sodimm's from crucial.

Crucial 16GB Single DDR3L 1600 MT/s (PC3L-12800) 204-Pin SODIMM Memory - CT204864BF160B

CT204864BF160B is a single 16GB DDR3L 1.35V Notebook module that operates at speeds up to 1600 MT/s and has a CL11 latency. It is dual voltage and can operate at 1.35V or 1.5V. It is Unbuffered and is non-ECC. It conforms to the industry standard SODIMM layout of 204 pins and is compatible with c...

www.amazon.com

These chips were first around in 2015, well after the 4771 Cpu and Imac were made, so maybe a recent update has sneaked some compatibility into the chipset.
I tried the chips in every combination with 10.14.6 no luck, but I did get it to read 24gb with just one 16gb and 8gb chip installed.
So on a separate drive I had the imac update to the newest 10.15.4 hoping that a new boot rom has some compatibility.
After updating the boot rom to 142.0.0.0.0
SUCCESS!
The Imac was able to read 48gb with 2x16gb chips and 2x8gb.

As far as I know, no one else has tried this, so I've orderd 2x more 16gb chips and see if it can reach 64gb.
Pretty happy that my hunch payed out and that these machines have ALOT more life ahead.

 

[TheSufle]

thanks for your answer! do you think imac 27 2014 also means it can work with 48gb ram?

 

[Thomasmasoniv]

thanks for your answer! do you think imac 27 2014 also means it can work with 48gb ram?

Try it!
I bet it works since the chipset is even newer.

This article from 2015 gave me hope since 16gb chips were known to work on X79 era 2011/2012 motherboards

"Motherboards that use the Intel X79 chipset can theoretically utilize 16 GB modules, though support for this is somewhat inconsistent -- the silicon supports it, though in most circumstances it requires a BIOS update."

With Catalina I think we got a low key bios update that has raised the amount of addressable Ram.

Kind of a big deal for all of us with 2012-2015 Imacs.

Big Data: Latest Articles, News & Trends | TechRepublic

www.techrepublic.com

 

[TheSufle]

Now I have 32gb 4x8 1866mhz, they work fine, will 2x16gb 1866mhz work or will 1600mhz be needed?
[automerge]1589122472[/automerge]
imac 2014 specs 1600mhz, but 1866mhz works too!
[automerge]1589122678[/automerge]
I will look forward to your test with 64gb, good luck!

 

[Thomasmasoniv]

Now I have 32gb 4x8 1866mhz, they work fine, will 2x16gb 1866mhz work or will 1600mhz be needed?
[automerge]1589122472[/automerge]
imac 2014 specs 1600mhz, but 1866mhz works too!
[automerge]1589122678[/automerge]
I will look forward to your test with 64gb, good luck!

Unfortunately today after a few hours I got Kernel panics with it in 10.14.6. I tried running it with 10.15.4 and it's still unstable. So at some point there is a degree of the CPU recognizing the Large ram chips but it's not able read from them entirely correct.

I checked the Dimm temp's and the 16gb chips do run a bit hotter than the 8gb chips. At 51C, but that shouldn't be effecting the system.

One thing I haven't tried is running it with Win10, and at this point I won't since I've played with this enough and these chips are going back in the mail before I brick my wife's Imac, but if somebody were to run Win10 and see if it's a MacOs limitation or Hardware compatibility that would be another clue. I kinda suspect it's a MacOS issue.

It would be interesting to try the same chip 16gb DDR3L 1600 chip on a 2014 or mid 2015 Imac. There may be more compatibility with the Haswell Cpu's, Don't know till we try?

Maybe with 10.16 coming later this year there will be another bootrom update and maybe these High capacity chips will work in older 2013 Imacs.

I got farther than I thought I would and getting the Imac to even boot with it was neat. Hope other people keep pushing it and I may try again in the future.

 

[FireFlyMx]

Hi Thomas! I also own a late 2013 iMac 27", and almost 3 years after your first post, I was wondering if you have more info about upgrading the RAM, did you perform more testing? any info is appreciated! thanks!

 

[FireFlyMx]

Unfortunately today after a few hours I got Kernel panics with it in 10.14.6. I tried running it with 10.15.4 and it's still unstable. So at some point there is a degree of the CPU recognizing the Large ram chips but it's not able read from them entirely correct.

I checked the Dimm temp's and the 16gb chips do run a bit hotter than the 8gb chips. At 51C, but that shouldn't be effecting the system.

One thing I haven't tried is running it with Win10, and at this point I won't since I've played with this enough and these chips are going back in the mail before I brick my wife's Imac, but if somebody were to run Win10 and see if it's a MacOs limitation or Hardware compatibility that would be another clue. I kinda suspect it's a MacOS issue.

It would be interesting to try the same chip 16gb DDR3L 1600 chip on a 2014 or mid 2015 Imac. There may be more compatibility with the Haswell Cpu's, Don't know till we try?

Maybe with 10.16 coming later this year there will be another bootrom update and maybe these High capacity chips will work in older 2013 Imacs.

I got farther than I thought I would and getting the Imac to even boot with it was neat. Hope other people keep pushing it and I may try again in the future.

Hi Thomas! I also own a late 2013 iMac 27", and almost 3 years after your first post, I was wondering if you have more info about upgrading the RAM, did you perform more testing? any info is appreciated! thanks!

 

[gilby101]

My advice is not to attempt more RAM than given by Everymac or OWC. For some 27" iMacs (e.g. my 2019) the reliable maximum RAM is greater than what is specified by Apple. But both those site give (for the 2013) 32GB as maximum that will work - I would keep to that.

 

[B S Magnet]

Hi Thomas! I also own a late 2013 iMac 27", and almost 3 years after your first post, I was wondering if you have more info about upgrading the RAM, did you perform more testing? any info is appreciated! thanks!

The optimal way to know is to do the experimenting and testing yourself — knowing full well the risk (well, more time than risk) in doing the work to swap out the RAM may not yield hypothesized outcomes. @Thomasmasoniv gave it a go and reported it didn’t work out, but didn’t do the more rigorous tresting of reviewing kernel panic logs or other RAM testing (like memtest) to determine why it didn’t work out. And from the look of it, @Thomasmasoniv wasn’t on here for long.

DIY experimenting and testing is how a lot of us on Early Intel Macs (soon to be the home of Ivy Bridge/Haswell iMacs) forum and the PowerPC Macs forum keep older and vintage Macs running well above and beyond what Apple intended or even planned.

So yes, give it a whirl and let us what you learn from testing it on your 27-inch model!

Pending on you and more folks doing this testing on the 27-inch variant (whose access to RAM is a lot easier than the same on the 21.5-inch variant, which is what I’m using at the moment), you might be able to help provide a clearer sense of the hardware and firmware’s limits with respect to RAM configurations.

Personally, I’d be curious to know whether a 27-inch model, despite having four RAM slots, could reliably run 32GB RAM on two slots; if so, then this could certainly open possibilities on the 21.5-inch models (with their two slots).

 

[TheSufle]

The optimal way to know is to do the experimenting and testing yourself — knowing full well the risk (well, more time than risk) in doing the work to swap out the RAM may not yield hypothesized outcomes. @Thomasmasoniv gave it a go and reported it didn’t work out, but didn’t do the more rigorous tresting of reviewing kernel panic logs or other RAM testing (like memtest) to determine why it didn’t work out. And from the look of it, @Thomasmasoniv wasn’t on here for long.

DIY experimenting and testing is how a lot of us on Early Intel Macs (soon to be the home of Ivy Bridge/Haswell iMacs) forum and the PowerPC Macs forum keep older and vintage Macs running well above and beyond what Apple intended or even planned.

So yes, give it a whirl and let us what you learn from testing it on your 27-inch model!

Pending on you and more folks doing this testing on the 27-inch variant (whose access to RAM is a lot easier than the same on the 21.5-inch variant, which is what I’m using at the moment), you might be able to help provide a clearer sense of the hardware and firmware’s limits with respect to RAM configurations.

Personally, I’d be curious to know whether a 27-inch model, despite having four RAM slots, could reliably run 32GB RAM on two slots; if so, then this could certainly open possibilities on the 21.5-inch models (with their two slots).

I doubt that someone will do this, will you buy expensive memory for the sake of experimentation?

 

[B S Magnet]

I doubt that someone will do this, will you buy expensive memory for the sake of experimentation?

With other, earlier Macs, I have — not just with RAM, but also with displays, backlighting, and AirPort-native solutions.

With the 2013 21.5-inch iMac I have now, I’m waiting to deal with hardware upgrades for when I can collect together everything at once (i.e., swapping the OEM HDD with a SATA SSD, populating the NVMe SSD slot with an m.2, upgrading the socketed CPU, and upgrading the RAM, all at the same time), since I really don’t have a lot of interest to buy a display adhesive kit for each of these individual upgrades.

So if someone else wants to tinker with their 27-inch variant, as RAM is fairly easy to reach on those models, their findings will go a long way to inform those of us with 21.5-inch models (whose RAM is accessible only after removing the logic board, after cutting into the display adhesive kit).

Otherwise, I’d take the initiative myself and share with the forum my findings, up or down, to give future folks a clear sense of what and how such upgrades fare. No experimentation assures no new ground can ever be (dis)covered.

Moreover, as RAM is also a commodity, selling good RAM which doesn’t ultimately work on your hardware is something one can do to recoup most of the outset expenditure.

 

[Nguyen Duc Hieu]

I doubt that someone will do this, will you buy expensive memory for the sake of experimentation?

2nd-hand SODIMM of 16GB are quite reasonably priced where I live. 35~45$ per stick.

 

[TheSufle]

2nd-hand SODIMM of 16GB are quite reasonably priced where I live. 35~45$ per stick.

then buy and test!

 

[TheSufle]

With other, earlier Macs, I have — not just with RAM, but also with displays, backlighting, and AirPort-native solutions.

With the 2013 21.5-inch iMac I have now, I’m waiting to deal with hardware upgrades for when I can collect together everything at once (i.e., swapping the OEM HDD with a SATA SSD, populating the NVMe SSD slot with an m.2, upgrading the socketed CPU, and upgrading the RAM, all at the same time), since I really don’t have a lot of interest to buy a display adhesive kit for each of these individual upgrades.

So if someone else wants to tinker with their 27-inch variant, as RAM is fairly easy to reach on those models, their findings will go a long way to inform those of us with 21.5-inch models (whose RAM is accessible only after removing the logic board, after cutting into the display adhesive kit).

Otherwise, I’d take the initiative myself and share with the forum my findings, up or down, to give future folks a clear sense of what and how such upgrades fare. No experimentation assures no new ground can ever be (dis)covered.

Moreover, as RAM is also a commodity, selling good RAM which doesn’t ultimately work on your hardware is something one can do to recoup most of the outset expenditure.

go ahead! I'll be waiting for your tests!

 

[FireFlyMx]

@B S Magnet Yeah you are right, and thanks for your comments, looks like we still have more to discover in these old machines, and only testing and research will answer the question. Unfortunately after looking around, here where I live and even online, the RAM upgrade would cost around $500-750 dollars, that's out of proportion, so I am sticking to my old ram for now until the prices drop in stores or I can find a good deal on second hand 16GB modules (and I will be actively looking for it). It seems like for now @Nguyen Duc Hieu has the advantage to perform more testing on that machine.

 

[B S Magnet]

@B S Magnet Yeah you are right, and thanks for your comments, looks like we still have more to discover in these old machines, and only testing and research will answer the question. Unfortunately after looking around, here where I live and even online, the RAM upgrade would cost around $500-750 dollars, that's out of proportion, so I am sticking to my old ram for now until the prices drop in stores or I can find a good deal on second hand 16GB modules (and I will be actively looking for it). It seems like for now @Nguyen Duc Hieu has the advantage to perform more testing on that machine.

I did some looking into this since you wrote, and I posted about it on a different, but somewhat parallel thread on the Early Intel Macs forum.

From what I now understand, the Haswell CPU is designed with two memory channels, each with a capacity of 16GB, for a total of 32GB. For purposes of trying to run between 32GB and 64GB on a Haswell CPU, it doesn’t look like it’ll work due to the design of the memory addressing.

What still isn’t self-evident or clear to me is whether that means, for Haswell CPU Macs with only two RAM slots, such as the late 2013 and late 2014 21.5-inch models (like my own), running 16GB modules in each of the two slots will work.

Alternately, for 27-inch iMacs with, say, four slots, but with one slot being bad, whether a single 16GB module on the channel with one bad slot and 2x8GB on the other channel, with the two good slots, will actually work out.

These all remain questions worth looking into for definitive answers in each scenario.

 

[TheSufle]

2017, 27-inch Retina 5K iMac - 128GB Ram Upgrade

I have successfully upgraded my 2017, 27-inch Retina 5K iMac with 128GB of Samsung DD4 2666MHz SODIMM ram. (4) Samsung 32GB DDR4 2666MHz sodimm of ram (M471A4G43MB1-CTD) Model Name: iMac Model Identifier: iMac18,3 Processor Name: Intel Core i7 Processor Speed: 3.6 GHz Number of Processors: 1...

forums.macrumors.com

imac 2017 has a similar theme, only it takes more volume, but does not work with it.

 

[Nguyen Duc Hieu]

I did some looking into this since you wrote, and I posted about it on a different, but somewhat parallel thread on the Early Intel Macs forum.

From what I now understand, the Haswell CPU is designed with two memory channels, each with a capacity of 16GB, for a total of 32GB. For purposes of trying to run between 32GB and 64GB on a Haswell CPU, it doesn’t look like it’ll work due to the design of the memory addressing.

What still isn’t self-evident or clear to me is whether that means, for Haswell CPU Macs with only two RAM slots, such as the late 2013 and late 2014 21.5-inch models (like my own), running 16GB modules in each of the two slots will work.

Alternately, for 27-inch iMacs with, say, four slots, but with one slot being bad, whether a single 16GB module on the channel with one bad slot and 2x8GB on the other channel, with the two good slots, will actually work out.

These all remain questions worth looking into for definitive answers in each scenario.

Haswell family include both LGA1150 (Celeron, Pentium, Core i) and LGA 2011-3 Xeon CPUs.
From Intel website, while LGA CPUs support up to 32GB RAM,
LGA 2011-3 Xeon CPUs support up to 768GB RAM.
For example, Xeon E5-1650 V3 has only 4 cores, but it does support up to 768GB RAM.

I don't have an iMac 2013 to test, but I did try 16GB SODIMM modules on my HP 800G1 USDT.
The RAM was not recognized.

 

[B S Magnet]

Haswell family include both LGA1150 (Celeron, Pentium, Core i) and LGA 2011-3 Xeon CPUs.
From Intel website, while LGA CPUs support up to 32GB RAM,
LGA 2011-3 Xeon CPUs support up to 768GB RAM.

Yes. This was an observation noted on the linked thread discussion from last day.

What was not resolved was whether the Haswell LGA/Core CPUs (released 2Q 2013 and later) had the same hardware design fix to allow the CPU to recognize and use RAM modules on DIMMs which ran larger than 4-gigabit.

The hardware design flaw/bug present on chip design, prior to the Ivy Bridge-E series (released 3Q 2013), limited the CPU to the 4-gigabit-per-module cap — meaning, a 16-module DIMM could, at most, have 8GB (i.e., 16 x 4 == 64 gigabits —> 8 gigabytes).

Because of Intel’s fix (and the fix’s timing into product cycles in 2013), what remains unclear is whether any of the Haswell LGA/Core models from 2013 or 2014 has this fix — to have up to 8-gigabit modules to be recognized — to allow a Haswell CPU to use, say, a 16GB DIMM. This would be something especially useful to know for those with Haswell LGA/Core systems with only one DIMM slot available per memory channel (e.g., the 21.5-inch iMac with two slots for two channels).

For example, Xeon E5-1650 V3 has only 4 cores, but it does support up to 768GB RAM.

Yup.

I don't have an iMac 2013 to test, but I did try 16GB SODIMM modules on my HP 800G1 USDT.
The RAM was not recognized.

This is helpful to know. Cheers.

Given the original post’s screen caps, it’s apparent that a memory channel on a 27-inch iMac can’t handle more than 16GB at a time before kernel panics or memory addressing corruption (whether configured as 16GB + 8GB or as 16GB + 16GB), but clearly their system booted and correctly recognized the presence of 16GB DIMMs. This would suggest — and correct me if I’m wrong — the late 2013 and possibly late 2014 iMacs can recognize DIMMs with modules greater than 4-gigabit (and which, if so, would permit a 21.5-inch model with only two slots to accommodate a pair of 16GB DIMMs).

 

[necessarynoise]

Hi there all. Very new to posting, but I use this site a lot for info. Today, I found a pair of 2x16GB modules very cheap, and I currently have 32GB in the 4x8GB fashion. I'm not super keen on trying what @Thomasmasoniv tried quite yet, however, I am interested in trying to see if my late 2013 iMac can support JUST the 2x16GB modules, at the 'supported' speed of 32GB. Does anyone like @B S Magnet have anything to chime in and say? I know the thread is a year old as of the last posting, but if there's been any updates since then, would love to hear it!

Any advice for testing things / processes?

 

[TheSufle]

Hi there all. Very new to posting, but I use this site a lot for info. Today, I found a pair of 2x16GB modules very cheap, and I currently have 32GB in the 4x8GB fashion. I'm not super keen on trying what @Thomasmasoniv tried quite yet, however, I am interested in trying to see if my late 2013 iMac can support JUST the 2x16GB modules, at the 'supported' speed of 32GB. Does anyone like @B S Magnet have anything to chime in and say? I know the thread is a year old as of the last posting, but if there's been any updates since then, would love to hear it!

Any advice for testing things / processes?

may work, but you will encounter problems with your computer and freezes, I wouldn't recommend it

 

[gilby101]

Any advice for testing things / processes?

Everymac https://everymac.com/systems/apple/imac/specs/imac-core-i7-3.5-27-inch-aluminum-late-2013-specs.html says max ram is 32GB. When Everyman quotes max RAM it is max RAM known to work with the model (not the max supported amount in Apple's spec).

Also OWC only sells 4 or 8GB modules. Another reliable guide as to what is possible.

So I would be surprised if it were to work with 16GB modules. Certainly not to work reliably.

 

[TheSufle]

2017, 27-inch Retina 5K iMac - 128GB Ram Upgrade

I have successfully upgraded my 2017, 27-inch Retina 5K iMac with 128GB of Samsung DD4 2666MHz SODIMM ram. (4) Samsung 32GB DDR4 2666MHz sodimm of ram (M471A4G43MB1-CTD) Model Name: iMac Model Identifier: iMac18,3 Processor Name: Intel Core i7 Processor Speed: 3.6 GHz Number of Processors: 1...

forums.macrumors.com

The answer to your question is more is possible, but it won't work

 

[Nguyen Duc Hieu]

Hi there all. Very new to posting, but I use this site a lot for info. Today, I found a pair of 2x16GB modules very cheap, and I currently have 32GB in the 4x8GB fashion. I'm not super keen on trying what @Thomasmasoniv tried quite yet, however, I am interested in trying to see if my late 2013 iMac can support JUST the 2x16GB modules, at the 'supported' speed of 32GB. Does anyone like @B S Magnet have anything to chime in and say? I know the thread is a year old as of the last posting, but if there's been any updates since then, would love to hear it!

Any advice for testing things / processes?

16GB DDR3 SODIMM modules can only works inside iMac 2015.
2013 & 2014 will not work.