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iMac Haswell + CL9 RAM @ 1.35V

I

IA64

macrumors 6502a
Original poster
Nov 8, 2013
552
66
So I ordered an iMac late 2013 maxed out ( 1TB Flash, core i7 and 780M ) except for RAM.

And now that I'm waiting for delivery, I spent 4 nights in row trying to check for RAM compatibily but I literally couldn't find anyone trying the CL9 @ 1.35V.

I've ordered the KHX16LS9P1K2/16 x2 ( 32 GB) for $406( Tax included ) :

Kingston Technology HyperX Lovo16 GB Kit (2x8 GB) 1600MHz DDR3 PC3-12800 Non-ECC CL9 SODIMM 1.35V.

Technical details :

PnP JEDEC TIMING PARAMETERS:
• DDR3-1600 CL9-9-9 @1.35V or 1.5V
• DDR3-1333 CL8-8-8 @1.35V or 1.5V
• DDR3-1066 CL6-6-6 @1.35V or 1.5V

Programmable CAS Latency: 11, 10, 9, 8, 7, 6

Row Cycle Time (tRCmin) 48.125ns (min.)
Refresh to Active/Refresh 260ns (min.)
Command Time (tRFCmin)
Row Active Time (tRASmin) 33.75ns (min.)

================================================

Ironically, Apple doesn't mention anything about voltage compatibility nor CL on their website.

Although CL9 will not be noticeably faster than CL11 for the average joe, but I run intensive, resource demanding applications ( 3 hours for each task minimum with file output > 10 GB ) So saving few minutes is welcomed.


From the informations I gathered I could confirm that :

- 2012 Macs can take CL9 @ 1600MHZ but @1.5V
- 2013 Haswell models are not stable with DIMMs @1.5V - overheat/crash
- 2013 Haswell models run smoothly @ 1.35v but with CL11 and some CL10
- 2013 Haswell models can run 1866MHz RAM @ 1.35V with no issue - CL11 / CL10

There has been reports related to kernel panic and system crash with CL9 @1.5V with Haswell CPUs however, none mentioned if it was due to the higher volatege or the lower latency.

The fastest RAM stick I could find was the HyperX Lovo KHX16LS9P1K2/16.

I find no reason why this should not work out of the box but I still have doubts and need some opinions here. I still have till Monday to cancel my order.

Thanks.
 
Last edited:
Jaguarxl

Jaguarxl

macrumors member
Nov 29, 2012
50
0
Brazil
Like you, I ordered latest iMac 27". But, I maxed out CPU and Gpu and upgraded to Fusion Drive 1Tb and left ram 8gb.

I'm ordering after doing some research trying to find a good memory upgrade. I found one from g.skill and I'm going to order a pair of 16gb (2x8). Not a cheap memory, but I believe it delivers! It's $20 cheaper at newegg. Sadly I can't buy one from them.... :(

16GB G.Skill Ripjaws DDR3 1600MHz SO-DIMM laptop memory dual channel kit (2x 8GB) CL9 - 9-9-9-28 / 1.35V
http://amzn.com/B00EOTYZOA

----------
Johnf1285 said:
I've had success on my 2013 27" i7 and G.Skill RipJaws running at CL 9 and timings of 9-9-9-28 at 1.35v

http://www.newegg.com/Product/Product.aspx?Item=N82E16820231705

Edit - now that I think about it I should probably boot into windows and confirm the voltage, timings, etc.

Will do later tonight when I get in from work.
Click to expand...

Nice!! I would like to hear from you how this memory goes!
 
MacOG728893

MacOG728893

macrumors 68000
Sep 10, 2010
1,715
114
Orange County CA
Johnf1285 said:
I've had success on my 2013 27" i7 and G.Skill RipJaws running at CL 9 and timings of 9-9-9-28 at 1.35v

http://www.newegg.com/Product/Product.aspx?Item=N82E16820231705

Edit - now that I think about it I should probably boot into windows and confirm the voltage, timings, etc.

Will do later tonight when I get in from work.
Click to expand...

You can confirm that these are running at the 1866MHz and stable? If so, why didn't Apple just give the higher end iMacs this clock speed from the get go?
 
J

Johnf1285

macrumors 6502a
Dec 25, 2010
965
61
MacOG728893 said:
You can confirm that these are running at the 1866MHz and stable? If so, why didn't Apple just give the higher end iMacs this clock speed from the get go?
Click to expand...

They run at 1600mhz out of the box. I haven't attempted to up it beyond that and am unsure how to since there isn't any sort of Bios to access (not sure if this is still true, but if I recall AMD systems really got the most out of higher clocked ram).
 
I

IA64

macrumors 6502a
Original poster
Nov 8, 2013
552
66
Johnf1285 said:
I've had success on my 2013 27" i7 and G.Skill RipJaws running at CL 9 and timings of 9-9-9-28 at 1.35v

http://www.newegg.com/Product/Product.aspx?Item=N82E16820231705

Edit - now that I think about it I should probably boot into windows and confirm the voltage, timings, etc.

Will do later tonight when I get in from work.
Click to expand...

Can you please check it with CPUz under bootcamp ? I would like to know if the iMac is running the RAMs at CL9 instead of CL11.

Looks like the G.skill is faster than the Kingstone Lovo with tRASmin = 28
 
J

Johnf1285

macrumors 6502a
Dec 25, 2010
965
61
So sorry just realized I do not have a copy of windows currently installed on this machine (I had to swap my iMac with Apple due to screen issues - the original had an installation). Will have some news hopefully tonight! Apologies on the delay!
 
I

IA64

macrumors 6502a
Original poster
Nov 8, 2013
552
66
Johnf1285 said:
So sorry just realized I do not have a copy of windows currently installed on this machine (I had to swap my iMac with Apple due to screen issues - the original had an installation). Will have some news hopefully tonight! Apologies on the delay!
Click to expand...

Bumpy bump
 
C

cpc6128

macrumors member
Oct 24, 2013
46
0
Can you let us know if 1866 ram is stable?

And has anyone got 32gb of OWC ram in their Haswell iMac with no issues whatsoever?
 
C

cpc6128

macrumors member
Oct 24, 2013
46
0
Guys, would it be safe to continue to use 2x8gb (16gb) Corsair Vengeance 1.5v in my iMac? It is not causing any Kernal Panics at all. (only when it's 32gb)
 
J

Johnf1285

macrumors 6502a
Dec 25, 2010
965
61
I can't find my thumb drive with Windows 8 on it. I'm having difficulties finding a direct ISO download from Microsoft for 8 (not 8.1 and not a .exe downloading program). I have a valid Win8 key.. Ah what to do...
 
I

IA64

macrumors 6502a
Original poster
Nov 8, 2013
552
66
Johnf1285 said:
I can't find my thumb drive with Windows 8 on it. I'm having difficulties finding a direct ISO download from Microsoft for 8 (not 8.1 and not a .exe downloading program). I have a valid Win8 key.. Ah what to do...
Click to expand...

Download Windows 7 ? http://technetwindows.blogspot.com/2012/10/windows-7-iso-download-free.html

Cheers.

----------
cpc6128 said:
Guys, would it be safe to continue to use 2x8gb (16gb) Corsair Vengeance 1.5v in my iMac? It is not causing any Kernal Panics at all. (only when it's 32gb)
Click to expand...

I'd always go for the 1.35V with the Haswell but again it' just me.
 
G

GXPvince

macrumors regular
May 12, 2008
114
0
Jag thanks for keeping up with that and letting us know the results. Good information to know when I get my new iMac.
 
Jaguarxl

Jaguarxl

macrumors member
Nov 29, 2012
50
0
Brazil
GXPvince said:
Jag thanks for keeping up with that and letting us know the results. Good information to know when I get my new iMac.
Click to expand...

You're welcome! I'm looking to test again with overclocked GPU, soon I can find some time to do that!
About memory, I noticed a lot of people complaining about Kernel Panic, random reboots, problems while trying to install new memories with common brands like crucial, kingston and corsair. The ones I read about using G.Skill ones didn't had any problems at all. I'm not saying the other brands are bad, but all the problems related to memories I didn't see anyone complaining about G.Skill.
 
C

cpc6128

macrumors member
Oct 24, 2013
46
0
The problem occurs when 32gb is installed. I had no problems with only 2x8gb 1.5v corsair vengeance - only when i all 4 sticks (32gb) i experienced issues.

I have got the owc ram (32gb) and no issues so far.
 
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