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1.5V or 1.65?

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June 3, 2011 9:13:03 PM

Hi all, can someone explain what this 1.5V or 1.65V is? which one should I use if i'm getting a z68 mobo?

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June 3, 2011 9:30:27 PM

The Sandy Bridge processor's memory controller is designed by Intel to interface with memory at a voltage of 1.5v. Intel has reported in the past that the acceptable maximum DRAM voltage is within 5% of the standard 1.5v, or 1.575v.

Many memory vendors are selling inexpensive DDR3 labeled to run at 1600MHz, but that require an input voltage of 1.65v to run stably. Many in the overclock and enthusiast community are weary of buying such memory -- there is a justified fear that by saving a few bucks on memory you may permanently damage/degrade the processor's memory controller.

However, if you do buy memory that will require 1.65v to run at 1600MHz, you will be fine running that same memory at 1333MHz at 1.5v. Moreover, you not notice the difference unless your primary use for the computer is showing off your benchmarks.

In terms of a recommendation, I would recommend buying memory rated to run at 1600MHz at 1.5v. On newegg, this information is always listed in the "specifications" tab.
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June 3, 2011 11:24:41 PM

do most people buy 1600Mhz memory?
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June 3, 2011 11:30:32 PM

velocci said:
do most people buy 1600Mhz memory?


There aren't any statistics on how many people run X speed of memory, so I can't answer that.
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June 4, 2011 12:48:28 PM

so is it a good idea to buy the fastest memory that runs on 1.5V? or is it a better idea to buy the fastest memory that runs on 1.65 volts, but only run it at 1.5V now and at the lower speeds and then later on when I want to overclock my machine, I have the option of running it at 1.65v and at the higher speed?
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a b } Memory
June 4, 2011 5:25:36 PM


Quote
Memory - Intel recommend 1.50v plus/minus 5% which means 1.60v is the ideal safe maximum, but we have found in our testing all 1.65v memory is fine. We have also found most new 1.65v like Corsair XMS3 will run at its rated timings with just 1.50-1.55v which is well within Intel specifications. So people upgrading to Sandybridge you can still use your old DDR3, but we do recommend you run it at 1.60v or less. We are shipping most of our bundles which feature Corsair XMS at 1.50v-1.55v at rated timings. We've also discussed with Asus and MSI regarding voltages for memory and they also confirm in their testing 1.65v caused no issues with reliability
End quote

Also: Quote
Sandybridge maximum safe voltages
Core Voltage - Not recommended too exceed 1.38v, doing so could kill the CPU, we therefor recommend a range of 1.325-1.350v if overclocking.

Memory Voltage - Intel recommend 1.50v plus/minus 5% which means upto 1.58v is the safe recommended limit. In our testing we have found 1.65v has caused no issues.

BCLK Base Clock - This is strictly a NO, anyone using base clock overclocking could/will cause damange to CPU/Mainboard. (Set manually to 100)

PLL Voltage - Do not exceed 1.9v!!
End quote.

About 4th post down. http://arstechnica.com/civis/viewtopic.php?p=21199063

!.5 V is better - that said. I have DDR3-1600 ripjaw CL7 @1.60 Volts in both my I5-750 and My New SB build.

In reference to speed and Cl timings. generally less than 5% boost in performance going from 1333 -> 1600, and also generally less than 5% for CL9 -> CL7. There are a very few apps that can take advantage of inceased BW (Speed) and lower timings.

That said, again my preference is for DDR1600. NOT if the memory is rated @ 1.5 V, but not totally stable you could always increase VDimm to 1.55V, BUT you should not do that with 1.65 V rated Ram.

PS. Intel plays it a little conservative with Voltage. I try to stay under the 1.65, but feel safe with 1.60. Higher speed ram (1600 and Higher) has only recently dropped below 1.65. The vast majority above the 1600 is still @ 1.65
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June 4, 2011 5:41:28 PM

so does it mean that buying memory rated at 1.5v means you can't overclock it later to higher speeds and using 1.65v?
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June 4, 2011 7:20:34 PM

velocci said:
so does it mean that buying memory rated at 1.5v means you can't overclock it later to higher speeds and using 1.65v?


Generally know. When they say "rated at 1.5v," that means "rated at the quoted speed at 1.5v."

If you can get 1600MHz at 1.5v, that means that you get get a better speed at Intel's maximum recommended 1.575v.
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June 4, 2011 9:51:26 PM

so is it a good idea to get fast memory that's rated at 2000Mhz at 1.65V and run it at 1.5v? or is it better to get memory rated at 2000Mhz at 1.5V?
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a b } Memory
June 5, 2011 1:44:51 AM

Because memory overclocking does very little for actual performance, you're better off buying some 1.5v 1333 or 1600 RAM and spending any extra money on a better graphics card or an SSD. At least that will make a noticeable difference.

If you fry your CPU and Intel finds out from testing that you were using RAM at higher than 1.575v, your warranty is void.
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June 5, 2011 11:03:00 AM

can you overclock the CPU without overclocking the memory?
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a b } Memory
June 5, 2011 1:42:54 PM

^
Yes. Reason is that with SB you overclock by raising the CPU multiplier, Not the Base Freq (100 Mhz for SB). With previous Intel CPUs the CPU was OCed by raising bclk and changing the multiplier.

When you raised bclk in the older cpus, it also raised the Freq to the memory, so unles you changed the multiplier to the memory (to a lower value) it would OC the memory. Ex. In my I5-750, I raised the bclk to 400 MHZ which means the lowest memory speed would be 800 (DDR3-1600). If I used DDR3-1333 I would have to OC it to DDR3-1600 to use the 400 Mhz bclk. But this is not the case with say a I5-2500k.

@ Leaps-From-Shawdows. Yes if you run above specs you void the warrenty. However; Last I knew it was about 30K dollars to determine the exact cause of failure in an IC. That was several years ago and the coust may have come down some, but still probably to high to be cost effective for a low value item.
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June 5, 2011 2:02:43 PM

ok I'm going to stick with 1.5v and be on the safe side. is there a good memory that's fast at 1.5v and that I can OC in a few years? the plan is to get the Asus P8Z68-V pro and the i7-2600k. then when the PC is getting old, instead of buying a new one, I buy a good heatsink/fan and OC the cpu to as high as it will go, OC the memory and buy an SSD. then it will be like i got a new PC for a fraction of the cost.
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a b } Memory
June 5, 2011 6:23:54 PM

The "OC the CPU" and "get a SSD" are very6 good at improving the performance. There is very little to gain by OCing the Memory.

I'm very partial to Ripjaw's DDR3-1600. I use their CL 7, But again little difference between CL-7 and CL9. If only 10% cost difference get the lower.

You didn't indicate 4 ,or 8 gigs. I recommend going with the 2 x 4, But
For 4 gigs 2 x 2:
For $62 -> 90: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
For $54: http://www.newegg.com/Product/Product.aspx?Item=N82E168...

For 8 gigs 2 x 4:
For $86: http://www.newegg.com/Product/Product.aspx?Item=N82E168...

What I have in I5-750 & I5-2500k systems: They are 1.60 volts and I have no qualms about using in my SB. Love them. NOT one problem, I just installed and in Bios selected use XMP profile 1.
2 ea 2 x 2 (8 gigs): No link, But idenital specs to 2 x 4
2 ea 2 x 4 (16 gigs): http://www.newegg.com/Product/Product.aspx?Item=N82E168...
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June 5, 2011 8:13:19 PM

sorry I forgot to say, i wanted the 4gb x 2. I looked on the Asus P8Z68-V Pro QVL list for memory and two of the listed memory are:
http://www.canadacomputers.com/product_info.php?cPath=2...

and

http://www.canadacomputers.com/product_info.php?cPath=2...

what do you think of those?

another question: on Asus's site, for the 1866mhz memory, it has (OC) in brackets, but for the 1600Mhz it doesn't. if i were to buy the 1866mhz memory, what would I have to do differently after installing the memory than for the 1600mhz memory?
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a b } Memory
June 6, 2011 2:05:28 AM

You would have to enable memory overclocking in the BIOS (enable X.M.P.)

On the voltage issue, I'm currently playing it safe with low voltage RAM; my initial Core i7-2600K blew up after two months of use when I was using 1.65V Corsair XMS3 RAM (Intel did RMA the chip even after I identified my RAM as 1.65V)
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a b } Memory
June 6, 2011 2:12:47 AM

SchizTech said:
(Intel did RMA the chip even after I identified my RAM as 1.65V)

Maybe Intel decided your CPU fried for some other reason. Others have had the RMA denied because the IMC failed due to excessive RAM voltage (1.65v).
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June 6, 2011 10:57:11 AM

so by putting in 1866Mhz ram and having to enable XMP, does that mean my ram will have to run at 1.65V?
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a b } Memory
June 6, 2011 1:32:37 PM

Go with the 1600 CL8. You will NOT see any difference in performance.
Bet my bottom Dollar that the "insides" of the two are Identical. What they have done is Upped the bandwidth (1866) and Downgraded the Timings and changed the XMP profile.
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a b } Memory
June 6, 2011 2:42:41 PM

Yes
Side Note, if you really wanted the 1866, you could probably use the 1600 and increase the timings to what is specified for the 1866.
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June 6, 2011 8:37:24 PM

ok so far i bought the corsair 8gb 1600Mhz cl9 memory and the i7-2600k. all i need now is the mobo and i'm set.
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June 6, 2011 8:59:51 PM

sorry I forgot, thanks alot for everyone's help, especially ReitiredChief. lets just hope my PC boots up properly after I build it.
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June 6, 2011 10:27:39 PM

out of curiosity, will a Z68 PC boot with DDR3 memory that's well under the 1600mhz speed? I was thinking that before I open my newly bought ram, I could test the motherboard with my DD3 I have lying around that's less than 1600mhz.
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June 6, 2011 10:36:30 PM

velocci said:
out of curiosity, will a Z68 PC boot with DDR3 memory that's well under the 1600mhz speed? I was thinking that before I open my newly bought ram, I could test the motherboard with my DD3 I have lying around that's less than 1600mhz.


Z68 supports the following:

DDR3 2200(O.C.)/2133(O.C.)/1866(O.C.)/1600/1333/1066

So as long as you're using 1066MHz or faster, you're fine to use it.
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