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

J

jobinho

macrumors newbie
Original poster
Oct 12, 2013
11
0
From what i've researched iMac's can handle both 1.35 V & 1.5 V RAM.

I'd like to know if either voltages is a better option for the Haswell iMac's.

Could adding 1.5 V potentially harm the computer or is 1.35 V more of a power saving measure?

My hunch is the 1.5 V in an iMac would be fine and 1.35 V would optimise a MBP.

I had ordered Kingston HyperX Plug & Play 1.5V http://www.amazon.co.uk/gp/product/B008H7IGGI/ref=oh_details_o01_s00_i00?ie=UTF8&psc=1 due to it's low latency but know of a more expensive 1.35 V version. I'm wondering whether it's worth getting a lower voltage module set to optimise my computers lifespan.

Any advice or opinion would be really helpful. ;)
 
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Lower voltage also translate into less heat generated. There's also a good chance the memory slots are only wired for the lower voltage.

Getting memory with a different CAS Latency than what is supported has a chance of not working or causing sporadic errors.

In this case I would definitely get memory at the supported voltage and would probably just stick with the supported CL.
 
Bear said:
Lower voltage also translate into less heat generated. There's also a good chance the memory slots are only wired for the lower voltage.
Click to expand...

I'd say there is ZERO chance of that, Bear. Haswell CPU's support 1.35 and 1.5v memory and Apple would have to try very hard to make 1.5v be a problem. Plus, they know that countless millions will install 3rd party ram and many of those millions will install 1.5v ram. Apple really don't want millions of RMA's and/or repairs to deal with, do they.

However, I agree with your recommendation to stick with the correct CAS and that 1.35v is the preferred option.
 
Chippy99 said:
I'd say there is ZERO chance of that, Bear. Haswell CPU's support 1.35 and 1.5v memory and Apple would have to try very hard to make 1.5v be a problem. Plus, they know that countless millions will install 3rd party ram and many of those millions will install 1.5v ram. Apple really don't want millions of RMA's and/or repairs to deal with, do they.

However, I agree with your recommendation to stick with the correct CAS and that 1.35v is the preferred option.
Click to expand...

I just ordered the new iMac with 8Gb RAM, because I´m planing to upgrade with cheaper memory modules. (Apple charges to much).
Doing some research, I found out the ideal is to buy memory modules with same CL as Apple originals (CL11). That´s if you plan to use together with original ones. Becouse different CL will make your imac run as it was 1333Mhz, not 1600Mhz, even if both modules are 1600MHz. Becouse the system tends to use the lower speed.
Correct if I´m wrong plz! But that was I found out researching over the internet for the best setup!:D
That´s ideal memory module I found:
Crucial CT2C8G3S160BM, 16GB Kit (8GBx2) DDR3 1600 MHz (PC3-12800) CL11 SODIMM 204-Pin 1.35V/1.5V
http://amzn.com/B008LTBJFW
 
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So, as per JEDEC DDR3L standard the 1.35V modules must be backward compatible to JEDEC DDR3 1.5V standards. Meaning 1.35V modules will be fine for a 1.5V application. This would lead me to believe that most memory companies are producing 1.35V modules by default to cut down on supply chain costs as they can produce 1.35V modules and sell them as 1.5V modules for marketing purposes. Haswell wants 1.35V.
 
Im sure i've read somewhere that the new iMacs ship with 1.5 V cl11 RAM. Would seem strange to advise against using 1.5 V if that were the case.

Can anyone verify this?
 
jobinho said:
Im sure i've read somewhere that the new iMacs ship with 1.5 V cl11 RAM. Would seem strange to advise against using 1.5 V if that were the case.

Can anyone verify this?
Click to expand...

Both Crucial and OWC claim the Late 2013 Haswell iMac is 1.35 V.
 
According to the Intel 4th generation CPU datasheet, memory interface voltages are as follows- direct quote:

DDR3/DDR3L I/O Voltage of 1.5 V for Desktop

The i7 4770k used in the 3.5GHz iMac can use 240 pin DIMMs at up to 1.65v, which is recommended for memory speeds between 2000 and 3000MHz.

The Haswell name is no longer used by Intel. They are now referred to as ARK CPUs
 
drambuie said:
According to the Intel 4th generation CPU datasheet, memory interface voltages are as follows- direct quote:

DDR3/DDR3L I/O Voltage of 1.5 V for Desktop

The i7 4770k used in the 3.5GHz iMac can use 240 pin DIMMs at up to 1.65v, which is recommended for memory speeds between 2000 and 3000MHz.

The Haswell name is no longer used by Intel. They are now referred to as ARK CPUs
Click to expand...

No iMac has a K cpu stock - the 3.5GHz iMac has an i7-4771.
The RAM speeds (2000-3000MHz) and voltage (1.65v) listed there are for overclocking purposes.
The official Haswell name is "4th Generation Intel Core Processor Family", not ARK.
ARK is simply Intel's online product catalog.
 
Bear said:
Getting memory with a different CAS Latency than what is supported has a chance of not working or causing sporadic errors.
Click to expand...
s6hb.png


Good thing that the JEDEC specifications make everything down to CL9 at 1600MHz mandatory.

What could cause trouble is 1866MHz RAM, but even that one ran fine on 2011 Macs already. However, the price for RAM is skyrocketing, and the 16GB 1866MHz Kingston HyperX Plug'n'Play kit is no exception.
 
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I have installed an extra 16GB in my new iMac, totaling in 32GB of ram.
I have put in Corsair Vengeance ram, and they are 1.5V.

So far I have no problems whatsoever and the iMac doesn't get hot at all. It's really great, the computer stays so cold!
 
Bear said:
I'd say hard wired for a specific voltage is a possibility. It has happened before.
Click to expand...

I don't know where it has happened before Bear. Do you mean with Apple?

Apple is such a huge company (obviously), it would be suicide for them to design the motherboard such that it would not work with 1.5v ram. The number of RMA's would run into the 1000's. And for what benefit? Makes no sense at all.

Personally I rule this out 100%. 1.5v ram will work fine, I am positive of it. And by way of anecdotal evidence, the 2012 iMac also ships with 1.35v, but countless thousands of people run 3rd party 1.5v memory without issues. Me, for one ;-)
 
So today I decided to call Apple care and they told me (after speaking to 2 dumb-asses) that I should use 1.35 cl11 RAM as it would optimise the longevity of my machine.

I've returned my Kingston HyperX and have ordered Crucial, I can forgo the 2% in memory speed anyway. Im sure all of you with 1.5/cl9 will be fine by the way, just my OCD risk limitation kicking in before I receive my rip-off computer.
 
jobinho said:
So today I decided to call Apple care and they told me (after speaking to 2 dumb-asses) that I should use 1.35 cl11 RAM as it would optimise the longevity of my machine.
Click to expand...

Not true, but I can't blame them for sticking to the book: say the wrong thing and customers go crazy.
 
Sam Spade said:
What problems would 1.35V CL9 cause? As noted, Apple recommends CL11...
Click to expand...

None. As stated upthread, 1.35V DIMMS can run at 1.5V. CL9 DIMMS are (effectively imperceptibly) faster, but can/will run at CL11 in a mixed environment.

There is no "danger" to having 2x 4GB 1.35V CL11 DIMMS and 2x 4GB "1.5V" CL9 DIMMS, although you'll find that most DDR3-1600 SODIMMS are 1.35V baseline.
 
elithrar said:
None. As stated upthread, 1.35V DIMMS can run at 1.5V. CL9 DIMMS are (effectively imperceptibly) faster, but can/will run at CL11 in a mixed environment.

There is no "danger" to having 2x 4GB 1.35V CL11 DIMMS and 2x 4GB "1.5V" CL9 DIMMS, although you'll find that most DDR3-1600 SODIMMS are 1.35V baseline.
Click to expand...

What you say seems logical (and its what I originally thought too) but it's not correct.

With the 2012 iMac (and I assume therefore also the 2013), if you mix memory types what happens is the iMac will run the memory at the fastest CAS timings (i.e. lowest CL number) and will clock the memory bus at whatever frequency the slowest stick can manage at those fast CL timings. This may seem odd, but it is what happens.

So what does this mean? Well for example suppose you have 8GB of Apple factory ram installed running CL11 @1600MHz and you add another 8GB of (say) Corsair 1600MHz CL10 memory. Instead of running at 1600MHz, CL11 - which is what you might expect to happen - in fact what happens is it runs at 1333MHz, CL10.

So it is important when mixing memory that you bear this in mind. If you add 1600 CL9 memory, you will actually make your system slower than if you add the (much cheaper) 1600 CL11 memory!

Of course if you are going to replace your Apple memory and only install fast memory, then none of the above applies.
 
Jaguarxl said:
I just ordered the new iMac with 8Gb RAM, because I´m planing to upgrade with cheaper memory modules. (Apple charges to much).
Doing some research, I found out the ideal is to buy memory modules with same CL as Apple originals (CL11). That´s if you plan to use together with original ones. Becouse different CL will make your imac run as it was 1333Mhz, not 1600Mhz, even if both modules are 1600MHz. Becouse the system tends to use the lower speed.
Correct if I´m wrong plz! But that was I found out researching over the internet for the best setup!:D
That´s ideal memory module I found:
Crucial CT2C8G3S160BM, 16GB Kit (8GBx2) DDR3 1600 MHz (PC3-12800) CL11 SODIMM 204-Pin 1.35V/1.5V
http://amzn.com/B008LTBJFW
Click to expand...

Is there a difference between that and this -> http://www.crucial.com/store/mpartspecs.aspx?mtbpoid=81CE351CA5CA7304

Other than price.
 
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