Mixing 2 x 1GB 800MHz with 2 x 1GB 1066MHz

Using Asus P5N-E SLI Mobo.


I currently have 2 x 1GB Corsair XMS2 800MHz DDR2 in there and someone is selling 2 x 1GB DDR2 Corsair Dominator 1066MHz and another person is selling 2 x 1GB Crucial Ballistix DDR2 1066MHz. No real reason why I'm getting 1066MHz, just that people were selling it on another forum for cheap.


I read that my mobo doesn't support 1066Mhz so it would downclock to 800Mhz. Is it okay to use one of the combinations above anyway?
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More about mixing 800mhz 1066mhz
  1. What are the rated Voltage requirements for the chips and the timings?? - although it is not a good idea to mix different speed RAM it can sometimes be done if they both can operate at the same Voltage (the faster RAM will downclock to run at the slower speed) as long as the higher speed RAM can also run at the same timings as the slower RAM at the slower speed.
  2. Hi, even if your mobo support 1066MHz when you install 1066 and 800, all the RAM run at the lowest speed.

    Now, you can install the 1066MHz RAM without problems, just make you sure that the voltage for all the RAM are the same.
  3. I'll guess I'll go with another 2 x 1GB of XMS2. Really how big of a difference is it with 4 x 1GB 800mhz vs. 4 x 1GB/2 x 2GB 1066mhz?


    Does the voltage matter if they're both the same exact speeds? My PSU is currently dead and I can't check my PC. I don't know which of these first two XMS2's on this page I have.

    http://www.newegg.com/Product/Produc...+x+1gb&x=0&y=0


    When you ask make sure the voltage of all the RAM are the same, do you mean change it so they're all the same in the BIOS? Or when I buy the new RAM make sure that's the same as the one I already have?
    So will the timings matter for the new RAM I buy with what I already have?
  4. Well, the difference between 800MHz and 1066MHz isn't big, in fact, is very small. So, the only difference that you can find, is the amount of RAM that you want install, isn't the same install 2GB 800MHz that install 4GB 1066MHz, in this case the difference is made for the amount of RAM and not for the speed.

    Yea, the voltage is important, usually DDR2 is 1.8V, and I think that your current RAM is at 1.8V, so, make your sure that you new ram is at 1.8V too.

    The timings are for performance, between more lowest the timing is, better is the RAM.
  5. saint19 said:
    Well, the difference between 800MHz and 1066MHz isn't big, in fact, is very small. So, the only difference that you can find, is the amount of RAM that you want install, isn't the same install 2GB 800MHz that install 4GB 1066MHz, in this case the difference is made for the amount of RAM and not for the speed.

    Yea, the voltage is important, usually DDR2 is 1.8V, and I think that your current RAM is at 1.8V, so, make your sure that you new ram is at 1.8V too.

    The timings are for performance, between more lowest the timing is, better is the RAM.

    Does the new RAM I buy have to match the RAM I currently have for timings? Or can I just change that in the BIOS without a problem if its already lower than the one I have?


    The same model I have right now is only being sold as 5-5-5-18 and 1.9V. It previously was 5-5-5-12 and 1.8V (what I have). So I can just find some 1.8V DDR2 800Mhz RAM and be good?
  6. The thing is all of your RAM needs to be run at the same Voltage and Timings - you can not set individual sockets to different speeds so if you mix modules they have to be similar enough that they can find a common setting to run at (and it will have to be the lowest voltage that they both can run at (otherwise one will have too much voltage and could burn out) and the slowest timings ( otherwise the system will be unstable ) - Also if they are too different and there is no common setting that they can run at the system may not boot at all - Hence the best method is to not mix Voltages or timings (speed ratings can be mixed because the faster rated modules can run at the lower speed if they are the same Voltage- but you lose some speed since the slower speed has to be used for all of the modules.)
  7. Unless I get the exact same RAM, I really can't find anything with the EXACT same timings. What would happen if I were to mix a 5-5-5-12 with 5-5-5-18?
  8. Derekkk said:
    Unless I get the exact same RAM, I really can't find anything with the EXACT same timings. What would happen if I were to mix a 5-5-5-12 with 5-5-5-18?


    Nothing, the problem is the voltage. But like I see, both are CL5,so, the voltage should be the same.
  9. As Saint19 said - they should be fine and be able to run at 5-5-5-18 as long as both sets run at the same VOLTAGE - that is the most important part since the Voltage seting has to be the same for all sockets on the MOBO and while some modules will run with more or less voltage than they are rated for you can not count on them being stable that way - some modules will run fine at a lower voltage others will continually CTD because of it - some modules will run fine with higher voltages but others will overheat and burn out from a slight voltage increase - SO you are taking a chance that they will not work together if you buy different Voltage rated modules !!

    On the timings those can be adjusted (loosened and any module an be made to run with others the thing is you will be limited to the slower speed that they can all run at (so if you buy a tightly times set of say 4-4-4-12 and another slow set at say 6-6-6-18 you will have to run the entire set of 4 at 6-6-6-18 and waste the money you spent on getting better timed modules (the lower latency willl cost more !) and you will need to understand how to set the timings to get them to work together (ie. installing the slower ones only at first adjusting the timing properly and then adding the others so that the system does not set them to the tighter timings by default and wind up ubable to boot.) and it may take some testing to get everything working together and correctly so unless you know your way around the BIOS and its settings it is best to get matching or very closely matched sets !!
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