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The general question is:
When installing low voltage RAM in a board that outputs a higher voltage to the memory module, will this fry the RAM or will it be like overclocking it?

My specific case is:
I have the Alienware m17xR3 laptop with a 2630QM Sandy Bridge board. Currently, I have the stock 1.5 V modules and when I check the overclocking options in my bios, the RAM voltage option ranges from 1.5 - 1.65 V. Is this simply because the bios recognizes that these are the values which my current RAM support and thus they will change when I install 1.35 V RAM or will I have to run the 1.35 V sticks at minimum 1.5 V?

If the case is the latter, would I fry my 1.35 V sticks? Or would they become automatically overclocked and get tighter timings with a higher voltage? Or both? Or neither? I'm a bit lost :p

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As far as I know, the voltage of the board in the bios shows the max voltage that can be drawn by the hardware, so if the RAM only draws 1.35, that's all it should use. I'm not 100% though so this is purely a comment, not an answer. –  Simkill Mar 11 '13 at 14:48
    
Thanks for the comment. I just found this over at anandtech, suggesting that they should at least not fry: "1.5V is a JEDEC spec and all DDR3 DIMMs have to follow it... Lower voltage ones often have their SPD report 1.5V to the BIOS, which is perfectly safe." I'm still interested in exactly what would happen though. –  cheflo Mar 11 '13 at 14:54
4  
@Simkill that's usually the case for current, from my EE studies. In the case of voltage, if the parts are only rated for 1.35v with less than a .15v tolerance, you could damage the RAM, if it can even be detected at all. –  BigHomie Mar 11 '13 at 14:58

2 Answers 2

up vote 8 down vote accepted

1.5V is the JEDEC standard for DDR3, therefore you will never fry a module at this voltage.

Some sources:

  • Hynix: "Hynix DDR3L SDRAM provides backward compatibility with the 1.5V DDR3"

  • Crucial refers to this as Dual Voltage: In the past, most DDR3 memory voltage ranged from 1.5 - 1.65v. More recently, dual 1.35/1.5 voltage modules came available at Crucial.com. The dual-voltage module will run only run at 1.35V if your specific system supports that voltage, otherwise the memory will run at 1.5V.

  • Kingston: As DRAM manufacturers shrink their dies and/or increase their yields of DDR3L, they soon reach a point where the majority of their DRAM output becomes DDR3L or dual-voltage, handling 1.5V or 1.35V voltages.

DDR3L (low-voltage DDR3) is just an "extension" of the DDR3 standard, so companies has to be aware that plugging a module will default to 1.5V on most systems. At 1.5V, the worst that will happen will be a waste of electricity/battery.

RAM modules contain pre-defined configurations (SPD, XMP, etc.) but the default one is often safer value that will work on as many systems as possible. For compatibility purposes, that setting might not be factory-set to 1.35V, but 1.5V instead. The default timings can also be different and slower from the ones indicated on your module package (I have an other answer on this topic).

For this reason, there's no chance it will overclock by itself even if it's running at a higher voltage (unless your current BIOS settings are manually set to run at specific speeds higher than your new modules would support - if so, reset your memory settings to AUTO before installing them).

If your RAM contains a XMP profile, try that as it can be factory set to 1.35 and all ideal settings - but you still have to select it manually in the BIOS.

In conclusion, 1.35V is perfectly safe. It's still always a good idea after installing RAM to go in the BIOS and verify/adjust the settings to ensure they match the module packages and perform optimally.

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This is a great response, thanks! I read about the dual crucial dual voltage support but I couln't find out if it was the case for all crucial 1.35 V modules or just specific ones. The one I'm looking at crucial.com/store/partspecs.aspx?imodule=CT2KIT102464BF160B wasn't listed as dual so I wasn't sure what would happen if it got 1.5 V. –  cheflo Mar 11 '13 at 16:10
    
You can always ask Crucial customer support to confirm for that specific module. But 1.35v is a improvement over 1.5V, not a limitation. –  mtone Mar 11 '13 at 16:29
    
Hehe, yeah i did that, but they didn't seem to understand my question, maybe because it's as you say with the Ferrari. At least they were able to confirm that the specific module will work on my system. –  cheflo Mar 11 '13 at 16:32
    
@cheflo they should be able to answer this question. Maybe ask again so you get someone else! –  mtone Mar 11 '13 at 16:40
    
@cheflo the recommended ram for your laptop on Crucial website are all 1.35v: crucial.com/upgrade/Alienware-memory/Alienware+Notebooks/… –  mtone Mar 11 '13 at 16:49

There's a reason they make low-voltage RAM, and it's not to run it at a higher voltage - it's so they use less power. Get the proper RAM, or RAM that's rated to at least the lowest voltage you can set (1.5V in this case).

It's impossible to objectively answer this question in general, but you can always refer to the manufacturer's datasheets, which should provide a range of operating voltages, clock speeds, and any relevant tolerances.

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Yes, I understand that the purpose of low voltage RAM is to save power and generate less heat. But since the cheapest 16 GB I can find actually is 1.35 V, I am interested if it will work or not. Running Crucial's memory compatibility tool shows a bunch of 1.35 V memories as compatible with my computer. Not the exact one I am looking at though... –  cheflo Mar 11 '13 at 15:15

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