i7 and 1.9v - 2.0v DDR3

stoofa · 16 Jan 2009 at 12:03

I haven't really been looking at i7 - some crazy high motherboard prices alone have made me wait until later in the year.

Anyhow, I see that all of the tripple packs of DDR3 contain modules designed to run at 1.5v - 1.65v.
So what is the situation with modules designed to run at 1.9v - 2.0v and using them on an i7 based system?

I would hope that motherboards out there give you the ability to run 1.9v - 2.0v through the DDR3 and not "over-volt" the CPU and cause problems.
Is this the case?
Or is it the case that simply put you cannot use DDR3 rated at 1.9v - 2.0v with an i7 based system?

RaiderX · 16 Jan 2009 at 12:14

apparently there is problems with memory thats higher than 1.7v that causes the cpu to burn out as the memory controller is built into the cpu now. personally i wouldnt try it

Stonedofmoo · 16 Jan 2009 at 12:17

Yeah from what I've read you can do it but your CPU won't last long.

Memory makers have been getting away with rating their sticks with more voltage for a long time now. It's about time the rated standard was enforced a bit more so they're forced to make better modules, not just overvolt them.

mmj_uk · 16 Jan 2009 at 12:57

The situation is that both the i7's onboard memory controller and RAM share the same voltage supply; and Intel warn of long term damage to the memory controller at anything above 1.65V.

stoofa · 16 Jan 2009 at 12:59

Now I must admit that is a little bit annoying.

I currently have an X38, Core2Quad based system.
I also have 8GB of G.Skill DDR3 1600MHz (CAS 7) RAM.
However the specification for this memory is 1.9v - 2.0v

So here I was thinking that a future i7 upgrade would be motherboard and CPU only.
I now find that because I've got the "wrong kind" of DDR3 I'll have to replace that as well.

Now that has put a downer on the day.

Stonedofmoo · 16 Jan 2009 at 13:05

I would try the sticks first Stoofa

You WILL be able to run them on a i7 board, it might just mean you have to relax the timings or speed they run at so they can run at 1.65v. That will allow you to continue using them.

azza21 · 16 Jan 2009 at 14:58

You need ram that doesn't go above 1.65, running your i7 at 1.90 will damage the internal bus. So i wouldn't go above 1.70 to be on the safe side.

shankii · 16 Jan 2009 at 15:01

not worth the risk, it might cause permanent cpu damage

Yellowbeard · 16 Jan 2009 at 19:16

FWIW, I have run our 1800C7 kits which are rated at 2.0v at 1600C8 at 1.65v. You will be able to use your existing RAM but as noted, you may have to run it at a different speed from stock. Then again, you may not. The only way to know is to try.

kazakore · 18 Jan 2009 at 15:35

How will putting RAM rated at a higher voltage actually increase the voltage? RAM is not a battery or power supply. Your motherboard regulates the voltages. Surely it will just supply your RAM with a voltage that isn't optimum, not end up delivering a too high voltage to the CPU. Or am I just crazy?

stoofa · 19 Jan 2009 at 11:21

I sent an email to G.Skill technical support on friday.
I received a reply this morning:

Dear customer

1.65v for F3-12800CL7D-4GBHZ you can run it around DDR3 1333 speed. But if you want to run This memory require 1.9v to run DDR3 1600 CL7

So basically this DDR3-1600 memory can probably be run at around DDR3-1333 at 1.65v.
I guess it means I can make the upgrade and then upgrade the memory in the future as I need it.

Still cannot believe this happened.
Wel actually I can - the computer industry just loves doing things like this.

Jokester · 19 Jan 2009 at 14:33

You can safely run high voltage RAM with i7 if you increase Vcore to minimise the potential difference between RAM and CPU apparently.

ashagplz · 19 Jan 2009 at 16:09

and theres basically no difference with the i7 with 1333 or 1600 memory.

Merlinbadman · 19 Jan 2009 at 16:22

ashagplz said:
and theres basically no difference with the i7 with 1333 or 1600 memory.

In what sense? Performance, cost, voltage?

My P6T came with a big sticker across the ram slots warning about using higher voltages than 1.65V.

ashagplz · 19 Jan 2009 at 16:26

in the sense that I7 cant make use of all the bandwidth. All the tests have shown there is basically no real world difference even between 800 and 1600 and the various timings.

fornowagain · 19 Jan 2009 at 16:33

Jokester said:
You can safely run high voltage RAM with i7 if you increase Vcore to minimise the potential difference between RAM and CPU apparently.

Not the Vcore, but yeah the VTT (QPI/DRAM Bus - what ever they want to call it now). I'll repost this from another post I made about 1.5v being the default value.

------------------------

This is a simplication. To be more accurate the voltage delta between the uncore VTT to vdimm should remain below 0.5v. The nominal QPI VTT of 1.1-1.2v gives the maximum 1.65v referred to above. The RAM you see for sale with 1.5v is designed to comply with the JEDEC standard.

http://www.intel.com/support/processors/sb/CS-029913.htm

Intel said:
What are the Intel® Core™ i7 desktop processors DDR3 memory voltage limitations?

Intel recommends using memory that adheres to the Jedec memory specification for DDR3 memory which is 1.5 volts. The Intel® Core™ i7 processors should not be used with DDR3 memory that is rated for voltage over 1.65 volts. Anything over this voltage can either damage the processor or significantly reduce the processor life span.

At your own risk of course, but 1.65v vdimm may not be the dead stop limit that some say it is, it can go higher without instant death. It just helps if you understand what causes the damage. VTT is the limiter and that has a stated maximum value of 1.35v.

Core i7 PDF > 2.10 Absolute Maximum and Minimum Ratings

Useful article on Nehalem Architecture.

While we were fearful about the memory overclockability of Core i7 CPUs we've found this not to be the case - we've hit 1,600MHz without even breaking a sweat on pre-production BIOSes and companies are already launching triple channel memory kits that are hitting 2,000MHz at a record low 1.65V. You can push the memory voltage, but Intel performance guru François Piednoel was keen to stress that the CPU voltage must be kept within a 0.5V potential difference to memory.

Comments from Intels François Piednoel (aka Drwho?)

François Piednoel said:
pajaa said:

Over at vr-zone is a preview of the Asus P6T Deluxe motherboard, which gives a strong warning not to raise the memory voltage higher than 1,65V, otherwise the CPU will be damaged permanently. Simple question: true or old information or can't you comment on this?

Click to expand...

I don't think it is accurate. Let's look at the logic behind memory controler...
Before, the memory controler was out of the CPU dice, so, if you burn a X48 ... it is only few 100 $ ... Now, the memory controler in on dice, so, if you burn, it will be expensive ... if using an extreme edition ...

So, electricly speaking, you want to pay attention to the laws of physics ... You got to make sure you align your memory voltage with the memory controler voltage ... I saw already people with illegitimate sample (grrrr) asking why their killed their CPU ... The reason is simple, if you put 1.5Volts on the memory controler, and 1.7 or 1.9V on the memory ... there is an obvious difference of electric potential ... and it will @#$!@#$*!#$

Any "non sunday overclocker" has a little understanding of physics laws, if you connect 2 wires with a different voltage ... you get electric courant.
In the case of Nehalem, you have to pay attention to this, don't connect 2 wires with different voltage together: Make sure your memory controler setting is not too far from the memory voltage.
On X48 , X35 and all the other, it was true too. People just burned chipset and did not really understood what was happening. This time, I come forward, and clarifie the laws of physics with the press, when I did meet them in Europe, USA and asia.