Setting RAM Timings & Voltage

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BirdIsTheWord33

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Feb 18, 2015
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I have a PC with 8GB of DDR3 RAM (2x4GB). I bought two more sticks of RAM (2x4GB) with very different specs, and I'd like to have them running alongside one another to create 16GB, if possible - I just don't want to fry any components.

Set 1: 1333 MHz / 9-9-9-24 / 1.5v
Set 2: 2133 MHz / 11-11-11-30 / 1.6v

My mobo only supports up to 1333 MHz, so I have to underclock Set 2 (which should happen by default). I don't think that the timings and voltage are adjusted along with the speed though - please correct me if I am wrong. It's also worth noting that my mobo supports two channels of RAM.

I want to get into the BIOS and set the timings and voltage manually, but I don't know what values to set the timings and voltage to for the best compatibility, and I didn't know if there was some way of calculating that information.

What values would work best, do you think? Can you explain why? Is this a terrible, terrible idea?

(Side note - I bought the new RAM with a friend who only needed 8GB more to match what he already had, so I got a steep discount overall but that is the reason why the specs of the new RAM far exceed those of my existing set.)

Thank you!
 
Solution
Darkbreeze
Since there is only one listed module @2133mhz shown for that board as being compatible, with 1.65v as it's nominal voltage, it could work, but probably would not work with an older CPU. I'd stick them in and see what it does by default. If it doesn't want to POST, but you're able to access the BIOS, you should be able to set the timings and voltages all the same and get dual channel operation from all four modules. I don't believe there is any potential for harm to your motherboard by attempting to use those modules at 1333mhz, 1.5v and 9-9-9-24 timings. It should work fine.

There is always the chance of incompatibility as I said, so if it doesn't want to POST or even boot to bios with them, it is what it is. There could also be...
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Darkbreeze

Darkbreeze

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Jun 24, 2014
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As per the G.Skill data sheet here: http://www.gskill.com/en/product/f3-17000cl11q-16gbxl

They DO have a 1600 SPD which can run at 1.5v, so theoretically you might be able to use them at 1333mhz speeds with the same timings and voltage as the other two modules, without any damage to the system. However, compatibility is another issue and you won't know without trying them. Whether your motherboard likes them or not is also another matter.

In reality, if your motherboard supported the profiled speeds of those modules you'd be better off just running them by themselves and ditch the 1333mhz modules. Unless you're running high end applications, virtual machines or some other off the beaten path processes, there isn't much benefit to running more than 8GB as there are no games that really use more than 4GB of system memory and the OS sure as hell doesn't. A RAMDISK or Virtual machine setup would benefit from it as would CAD software, otherwise, it's nice to know it's there, and that's about it.

Again, what is your motherboard model number and I'll tell you if it even supports those modules.
 
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Darkbreeze

Darkbreeze

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Jun 24, 2014
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Since there is only one listed module @2133mhz shown for that board as being compatible, with 1.65v as it's nominal voltage, it could work, but probably would not work with an older CPU. I'd stick them in and see what it does by default. If it doesn't want to POST, but you're able to access the BIOS, you should be able to set the timings and voltages all the same and get dual channel operation from all four modules. I don't believe there is any potential for harm to your motherboard by attempting to use those modules at 1333mhz, 1.5v and 9-9-9-24 timings. It should work fine.

There is always the chance of incompatibility as I said, so if it doesn't want to POST or even boot to bios with them, it is what it is. There could also be density differences between the older chips and those ones. You might end up with modules just worth holding on to for a future upgrade if that happens.
 
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Solution
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BirdIsTheWord33

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Feb 18, 2015
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Perfect. I seem to have got the two sets of RAM working together - these are the steps I took.


    Booted into the BIOS with only the old RAM inserted and made note of the values in the memory section. They were as follows:

    • Multiplier: DDR3-1333

    • Voltage: 1.5v

    • tCL: 9

    • tRCD: 9

    • tRP: 9

    • tRASmin: 24

    • tRFC: 107

    • tRRD: 4

    • tWR: 15

    • tWTR: 5

    • tRTP: 5

    • tRC: 15

    • tFAW: 20

    • Command Rate: Auto


    Shut down the computer, removed the old RAM, inserted the new RAM, and booted into the BIOS.


    I took a look at the new memory values - mostly all of the values had increased from the old RAM. To my surprise, the multiplier was set at DDR3-1600. Apparently this motherboard does support memory running at that speed, though it is stated that it doesn't. The voltage was still at 1.5v, though.


    I changed all of the values to match the values given when running the old RAM.


    I rebooted and made sure that the new memory was working with these new values.


    I turned off the computer, installed the old RAM alongside the new RAM, and booted into the BIOS. It recognized that there was 16GB of RAM installed.


    I booted into Windows, checked to see that all 16GB was recognized.


Everything seems to be in working order. Nice! One question - should I have changed the Command Rate value from Auto to something else? Will I potentially run into issues if it is kept on Auto?

Thanks again for all of your assistance - it's been super-helpful. If you have any time to explain what the tRFC, tRRD, tWR, tWTR, tRTP, tRC, tFAW and Command Rate values are, I'd be interested in learning. I like to know what it is I'm doing when I'm messing around with my PC, especially in the BIOS. If not, though, I understand.
 
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Darkbreeze

Darkbreeze

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Jun 24, 2014
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Most of the settings should remain on auto, to avoid compatibility issues. If the old RAM tried to run at DDR3-1600 speeds, you might actually be better off to try running ALL of the modules at DDR3 1600, 1.5v, and whatever the timings were automatically set at when it was running at that speed. For a better understanding of the RAM settings you can check this out:

http://www.hardwaresecrets.com/article/Understanding-RAM-Timings/26


http://forums.tweaktown.com/gigabyte/27283-memory-timings-explained-w-suggested-timings-memset-vs-bios.html
 
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