Re: RAN 1.35v vs 1.5v

micky wrote:
> In alt.comp.hardware, on Tue, 26 Jan 2021 19:22:59 -0500, Paul
> <[email protected]> wrote:
> 
>> micky wrote:
>>> I wanted to get more RAM for my newly-acquired PC
>>> Entering the make and model, HP EliteDesk 800 G1 Small Form Factor
>>> Crucial suggests only CT2K102464BD160B
>>> DDR3 PC3-12800 • CL=11 • Unbuffered • NON-ECC • DDR3-1600 • 1.35V •
>>> 1024Meg x 64 •       $76 even cheaper at NewEgg,  
>>> Kingston suggests only KCP316ND8/8
>>> Specs: DDR3, 1600MHz, Non-ECC, CL11, X8, 1.5V, Unbuffered, DIMM,
>>> 240-pin, 2R, 4Gbit   $98
>>> The items are in different order but the main difference seems to me to
>>> be  1.35v vs 1.5v.   
>>> That seems important, right?  How can they be different for the same
>>> computer?   (I'm not really concerned about price unless they could sell
>>> it cheaper by making it at the wrong, lower voltage. )
>>> Do I need to look up what the computer puts out?   Would one of these be
>>> overclocked if the computer puts out 1.5v and the other underclocked if
>>> the computer puts out 1.35? 
>>> I already have 2 sticks,  Do I want to get the same voltage that they
>>> use, whatever that is? 
>>>    ------
>>> Other differences are 
>>>   Crucial says PC3-12800 but Kingston doesn't include that.  
>>>   Kingston says X8, 2R, 4Gbit but Crucial doesn't include any of that. 
>>> Does any of that matter? 
>>>    ------
>>> FTR, I only looked at Newegg because Crucial was out of stock. NewEgg
>>> says "Ships from China. Newegg Most customers receive within 10-32
>>> days."
>>> Hmm.  At
>>> https://www.newegg.com/crucial-16gb-240-pin-ddr3-sdram/p/N82E16820156047
>>> it says sold and shipped by Ram-Store and when you click on 12 New from
>>> $88.46 , it goes to the bottom of the page where they have 12 vendors
>>> selling the same thing.  Just like Amazon does it. I only looked at the
>>> first 5 but one is in Hong Kong and "Most customers receive within 4-17
>>> days.".  One is in the US and "Most customers receive within 7-9 days",
>>> all except Hong Kong for the same price!! (For Hong Kong and the next 7
>>> the price gets higher.)
>>> But this doesn't matter until I understand the voltage question. 
>> 1.35V DIMMs run in a 1.5V motherboard.
>>
>> There should be a FAQ with the details around somewhere.
>>
>>    https://superuser.com/questions/564175/1-35-v-ram-in-a-1-5-v-system-will-it-fry-or-overclock
> 
> First answer is:  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.

If your machine uses SODIMMs, I must have selected the wrong
item from the Crucial list.

If you have part numbers on the existing modules and you're
happy with them, then that's likely just as good of a
choice as anything else. If you got "fancy" products with
low CAS, they wouldn't help, because the slowest memory
in the machine determine the speed choice made by the BIOS.

But if supplies were limited (like the Crucial being out of
stock), I was looking around to see what could be fitted
from the existing pool of product.

I'm really surprised you can find branded Samsung DIMMs/SODIMMs.
Samsung sells product more to businesses than to end users.

The SPD table shows what the DIMM expects in terms of voltage.
The SPD chip receives power right away, and the BIOS reads the SPD.
The BIOS "turns on" the VDIMM regulator, only when it has
determined what the strategy is. So RAM is "commissioned"
by the BIOS POST process - and some of the BIOS code
runs without RAM for storage, and variables are stored
in CPU internal registers.

If the BIOS is unhappy with what it reads in the SPD table,
it will "beep". And occasionally a poster will post a question
about a BIOS that is beeping, when it should not. And in some
cases, it tries to match fields in the SPD that are
"don't cares". That means poorly prepared SPD table
contents, can result in surprises for users. One DIMM even
had the wrong SPD chip soldered to it :-) Clever.

    Paul