1.35 V & 1.5 V RAM for late 2013 iMac's

[IA64]

I don't beiieve that for 1 nanosecond.

First, there are countless people running 4 x Corsair 1600 CL10 1.5v in 2012 imacs and some in 2013 without problems. The 2012 and 2013 share the same power supply and the Haswell chips use give or take the same amount of power.

Second, the incremental power consumption of running at 1.5 instead of 1.35 volts is negligable. Around 3w total across the 4 sticks, and WAY less than the extra power used for example by overclocking the video card, which many people have tried and which works without issue. (Incidentally, that's 3w under full load. A fraction of that on idle - perhaps 0.1w).

Third, Apple - normally a very conservative bunch - state that 1.5v ram is fine in Haswell iMacs.

It is FAR more likely (strike that, it is an unavoidable conclusion) that people having issues with 4 x 1.5v sticks are down to compatibility of the specific brand and type of sticks themselves, rather than the voltage per se.

1&2 )

It's not the Power Supply, it's the logic board.

According to your logic, 3W is negligible; in other words, oveclocking RAM to 1.65V ( additional 6 Watts only ) should not cause any issue because the PS can deliver it.

That's absolutely not true. Some boards do support overclocking, some other don't, hence the reason behind it.


3) If 1.5V was fine, they would have shipped it with a 1.5V RAM which is cheaper than the 1.35V anyday.

Again all late 2013 iMac compatible RAMs are rated at 1.35V... not a coincidence eh? Earlier iMac come with 1.5V modules.

Long story short. 4 modules of 1.5/1.65V RAM will not work on a late 2013 iMac no matter which brand you take.

1.35V or 1.35/1.5V is your best bet.

I don't really care what Apple has to say about it; take it from someone who has tried it be it a 1.35,1.65,1.5V RAM. I also tried the 1.35V 1866MHz CL10 RAMs and surprise, it works. How come Apple said it's unsupported ?

I am currently running a PC12800 CL9 Kingston HyperX but wait, Apple recommends CL11 only... Well, sorry but I've been using Apple computers since 2004 and I can guarantee you that Apple doesn't tell you everything.

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Which program (free) should I use to have such information ?

I usually use CPUz under Windows.

Under Mac I think TechTool Pro 7 will do the job.

 

[SaSaSushi]

There is evidence to support both sides of this argument. I actually did experience a kernel panic earlier this evening with the 32GB including new 1.35 V RAM. It was my first one on this machine since I had the 1.5 V RAM in it. However, I am inclined to believe that this particular crash was because of a separate problem I have been dealing with regarding USB compatibility with Haswell iMacs and Fusion Drives. I had those lockups in the past even with just the stock RAM.

So, I will keep using the machine and see how it runs. It could also be that the iMac doesn't like the brand of RAM I've added. I definitely see a big difference though in overall stability with this 1.35 V to the 1.5 V. With the 1.5 V I was getting almost dependable shutdowns when I used my flash web conferencing app. This is not the case with the 1.35 V, not yet at least and I've been running it pretty hard today.

 

[jomanlo]

I usually use CPUz under Windows.
Under Mac I think TechTool Pro 7 will do the job.

I am not under Windows (I knew CPUz) and under Mac TechTool Pro is not free, does anybody else know a free tool to check voltage?

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So, I will keep using the machine and see how it runs. It could also be that the iMac doesn't like the brand of RAM I've added. I definitely see a big difference though in overall stability with this 1.35 V to the 1.5 V. With the 1.5 V I was getting almost dependable shutdowns when I used my flash web conferencing app. This is not the case with the 1.35 V, not yet at least and I've been running it pretty hard today.

I never mixed ram on any computer (PC or Mac). I always changed all DIMMS.
You can have too many different parameters in my opinion, Brand/Size/Voltage/Timings/... so I think full compatibility can not be assured.

I would recommend people who are having troubles to make tests with only same brands dimms in order to be sure to get the right information.

 

[GSVNotInvented]

Use 1.35v DDR3L SO-DIMMS

Hello all,

I have 3x late 2013 27" i7 iMacs with 32Gb Kingston RAM fitted in each. RAM was 1.5v.
All 3 had random kernal panics at least twice a day.
Removed 16Gb RAM. All 3 iMacs are stable.
Replaced all 12 SO-DIMMS with 1.35v Kingston sticks and each machine is back to 32Gb and running fine. No kernal panics.
Use the 1.35v DDR3L SO-DIMMS.
Hope it helps.

 

[Chippy99]

1&2 )

It's not the Power Supply, it's the logic board.

According to your logic, 3W is negligible; in other words, oveclocking RAM to 1.65V ( additional 6 Watts only ) should not cause any issue because the PS can deliver it.

That's absolutely not true. Some boards do support overclocking, some other don't, hence the reason behind it.


3) If 1.5V was fine, they would have shipped it with a 1.5V RAM which is cheaper than the 1.35V anyday.

Again all late 2013 iMac compatible RAMs are rated at 1.35V... not a coincidence eh? Earlier iMac come with 1.5V modules.

Long story short. 4 modules of 1.5/1.65V RAM will not work on a late 2013 iMac no matter which brand you take.

1.35V or 1.35/1.5V is your best bet.

I don't really care what Apple has to say about it; take it from someone who has tried it be it a 1.35,1.65,1.5V RAM. I also tried the 1.35V 1866MHz CL10 RAMs and surprise, it works. How come Apple said it's unsupported ?

I am currently running a PC12800 CL9 Kingston HyperX but wait, Apple recommends CL11 only... Well, sorry but I've been using Apple computers since 2004 and I can guarantee you that Apple doesn't tell you everything.

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I usually use CPUz under Windows.

Image


Under Mac I think TechTool Pro 7 will do the job.

There's a lot of stuff in your post (much of it I disagree with) but to be honest I can't be bothered replying to all of it. I posted what I posted to try to be helpful and really do not want to get into a point by point argument.

But a couple of things:

1. Earlier Macs shipped with 1.35v as well
2. 1.65v isn't supported by Intel let alone anyone Apple
3. I said an extra 3w is fine, not an extra 6w. And it's about 7w going to 1.65v
4. "I don't really care what Apple has to say about it; take it from someone who has tried it" - good grief, so your experience with what 3 sticks >> Apple Computer Corporation. How arrogant of you. They might not tell you everything but they are not going to tell you something works when it does not.
5. This has nothing to do with overclocking.
6. 1866 Ram is not supported either. The fact that "it works" is irrelevant and not the point.
7. Haswell chipset supports 1.5v and the Apple logic board is an Intel compliant design with appropriate power supplies and voltage regulation. It is unlikely to the point of impossible that the board would not run 1.5v ram but would be in every other way perfectly stable.

 

[SaSaSushi]

I am not under Windows (I knew CPUz) and under Mac TechTool Pro is not free, does anybody else know a free tool to check voltage?

The 14-day free trial of iStat Menus will tell you the voltage. It's an awesome app I've purchased and highly recommend by the way.

I never mixed ram on any computer (PC or Mac). I always changed all DIMMS.
You can have too many different parameters in my opinion, Brand/Size/Voltage/Timings/... so I think full compatibility can not be assured.

I was very careful to buy RAM with precisely the same specs as the Apple stock modules. I have confirmed with TechTool Pro that they are identical down to the last very last SPD timing.

I'm happy to report that I got through an entire workday with the new RAM, and aside from the abovementioned kernel panic that was identical to ones I was experiencing previously with only the 16GB of stock RAM, I have had no problems to speak of.

Even if it turns out that there is a compatibility issue with these modules, and I'm cautiously optimistic it will not, this time around it is far more stable than when I had the 32GB with 1.5 V.

I am adding my name to the list of those recommending to go with DDR3L only on the Haswell Macs.

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1. Earlier Macs shipped with 1.35v as well

They did indeed, but these voltage sensitivities seem to be related to the Haswell chipset.

7. Haswell chipset supports 1.5v and the Apple logic board is an Intel compliant design with appropriate power supplies and voltage regulation.

Actually, mobile Haswell-based CPUs don't support 1.5V RAM.

I still can't get a definitive answer on whether the iMac uses mobile processors or desktop parts. According to EveryMac, it is the "Mobile Core i7 "Haswell" (4771) processor with quad cores (four independent processor cores on a single silicon chip, each with one thread)"

 

[jomanlo]

The 14-day free trial of iStat Menus will tell you the voltage. It's an awesome app I've purchased and highly recommend by the way.
"

Thank you for the info, I will try it

 

[Chippy99]

I still can't get a definitive answer on whether the iMac uses mobile processors or desktop parts. According to EveryMac, it is the "Mobile Core i7 "Haswell" (4771) processor with quad cores (four independent processor cores on a single silicon chip, each with one thread)"

It's a 4771 and the 4771 is a desktop part, as per the previous generation 2012 iMacs which also used desktop parts.

 

[jomanlo]

I installed IStats and my ram seems to run at 1,5V, as announced by Corsair.

I also performed a memory test with TechTool Pro 7 and there were no errors.

 

[IA64]

I installed IStats and my ram seems to run at 1,5V, as announced by Corsair.

I also performed a memory test with TechTool Pro 7 and there were no errors.

Looks like iStats reports incorrect voltage across the RAM.

Mine is 1.35V but iStats shows 1.5V also. Under Windows it's 1.35V as shown in CPUz

 

[SaSaSushi]

Looks like iStats reports incorrect voltage across the RAM.

Mine is 1.35V but iStats shows 1.5V also. Under Windows it's 1.35V as shown in CPUz

Yeah, it's weird. When I checked iStat Menus yesterday it was reporting around 1.15 V to 1.30 V but now shows 1.5 V. Nevermind iStat for the voltage testing.

TechTool Pro shows the correct 1.5 V. I have CPUz in BootCamp and I will also run that to confirm but I'm sure the RAM is now all running at 1.35 V.

 

[SaSaSushi]

I checked in Windows 7 Boot Camp and have confirmed that all of my RAM is now running at 1.35 V.

I also found out that the kernel panic I experienced yesterday was most likely due to an outdated driver for Tuxera NTFS I had loaded. I've since uninstalled it and have experienced no further problems yet.

 

[jomanlo]

Looks like iStats reports incorrect voltage across the RAM.

Mine is 1.35V but iStats shows 1.5V also. Under Windows it's 1.35V as shown in CPUz

I also checked with TechTool Pro 7 and it also says 1,5v for me, normal as my ram is annouced at 1,5v.

 

[IA64]

I also checked with TechTool Pro 7 and it also says 1,5v for me, normal as my ram is annouced at 1,5v.

Same here. TTP 7 reports 1.5V whereas my RAM is running at 1.35V

Looks like both iStats and TTP read from the same source whatever it is.

Could be also a bug with Mavericks. No idea tbh.

 

[jomanlo]

Same here. TTP 7 reports 1.5V whereas my RAM is running at 1.35V

Looks like both iStats and TTP read from the same source whatever it is.

Could be also a bug with Mavericks. No idea tbh.

If someone knows another program under OSX to check voltage more precisely I could check again. I do not have Windows on my Imac, cpuz was nice...

 

[Rogier1991]

I'm following this topic quite some time, because I want to upgrade my RAM in my 2013 27 inch iMac, these are my options:

- G Skill F3-1866C10D-8GRSL (8GB, 1.35 voltage, 1866 Mhz and 10-10-10-32)
- G Skill F3-2133C11D-8GRSL (8 GB, 1.35 voltage, 2133 Mhz and 11-11-11-36)

Anybody checked if 2133 mhz will be working on the iMac?

 

[SaSaSushi]

I'm following this topic quite some time, because I want to upgrade my RAM in my 2013 27 inch iMac, these are my options:

- G Skill F3-1866C10D-8GRSL (8GB, 1.35 voltage, 1866 Mhz and 10-10-10-32)
- G Skill F3-2133C11D-8GRSL (8 GB, 1.35 voltage, 2133 Mhz and 11-11-11-36)

Anybody checked if 2133 mhz will be working on the iMac?

I suspect from what I've read that the max speed RAM will run at on the Haswell Macs is 1866Mhz. Therefore, even if you installed the 2133Mhz it would probably only run at 1866Mhz.

One thing is for sure. These iMacs seem to be extremely difficult with RAM compatibility. I had another kernel panic last night, this one pointing to Parallels but I've never had any issues with it before.

I reseated the RAM (one of the modules may not have been seated properly) and have now been trying my hardest, unsuccessfully thus far, to cause it to panic again. Three strikes and it's out for a refund.

If I end up returning this new RAM I will probably just hold off on upgrading at all and go with 16GB until the RAM prices drop again and order the Crucial from Amazon US.

 

[SaSaSushi]

Sadly, I had yet another kernel panic this morning and the honeymoon is over. I've removed the RAM and will send it in for a refund.

The panics point to Parallels every time, but they never occur with only 16GB of Apple RAM installed.

There are many, many reports of problems with system instability due to the mixture of DDR3 and DDR3L RAM and I still firmly believe one is best advised to stick with DDR3L RAM only with the Haswell iMacs. After all, this is what Apple themselves ship the machine with.

That said, the Haswell iMacs do seem to be extremely finicky with upgrade RAM period. I've even seen a few reports on the Crucial forums of their popular Apple-compatible DDR3L at 32GB causing kernel panics. They seem to be in the minority, but they're still out there.

So I'm not sure what my next step will be. This is the first Mac I've ever experienced these problems with.

 

[jcr918]

After my one issue I haven't had anymore crashes. Knock on wood I think my system is stable at 32GB or ram

 

[SaSaSushi]

After my one issue I haven't had anymore crashes. Knock on wood I think my system is stable at 32GB or ram

Glad to hear that. Just to confirm because I think you may have mentioned it in another thread, you're using the Crucial RAM from Amazon mixed with stock Apple RAM?

 

[mogens]

Arghh..just ordered a 2013 27" imac with stock 16GB ram. Thought that the diy upgrade to 32GB would be piece of cake. Reading this makes me nervours, guess I should have ordered it with 32Gb in the first place

 

[SaSaSushi]

Yet another update. I just can't shake the very strong feeling that the third party RAM I've been installing is not to blame for these problems.

Since it is the weekend here and I can't return the latest 16GB of DDR3L that I purchased until start of business on Monday morning, I decided to try one last experiment. I removed all the DIMMs and then put them back in one by one, seating them as firmly as I could. I also put the third party RAM in the slots the Apple RAM occupied, reversing them.

So now it's been 12 hours of me trying my hardest to invoke a kernel panic, so far unsuccessfully. The real problem is that there is never one definitive way to get the machine to panic. It does so randomly. I've got another 24 hours to stress test it and I half hope it does panic again, because if not I will have a more difficult decision on returning it or not. I have to pay all the shipping and fees for the RMA and I got this RAM at an excellent price.

I just have this sinking feeling that even if I do return it and order the Crucial from the states, it will end up with a random kernel panic about a day in. Then I'll pull my hair out.

Again, this iMac is the prettiest and fastest I've ever owned but it is also by FAR the most troublesome.

 

[lawlawman]

All

I installed 2 packs of Corsair (CMSA16GX3M2A1600C11) for 24 hours. So far so good.

According to the product information, these pairs are DDR3L.

Are there any stress test I can try so that I can share the test result here?

Cheers.

Gary

 

[SaSaSushi]

All

I installed 2 packs of Corsair (CMSA16GX3M2A1600C11) for 24 hours. So far so good.

Glad to hear that, Gary! Did you add 16GB for a total of 32GB? Also, was this in addition to the Apple stock RAM? All of this information is vital to tracking down exactly what the cause of this instability might be for those of us suffering with it.

Are there any stress test I can try so that I can share the test result here?

I wish there was! I've tried everything I can think of but it seems my panics, spontaneous reboots and/or freezing were basically random.

15 hours and counting now without a freeze, but it's gone longer in the past.

 

[lawlawman]

I removed the stock modules and installed 4 corsair modules.