what happens when you put two different types of ram i.e(PC2700 and PC3200) together into one machine?

I have 4 sticks of DDR DIMM. Two onf them are PNY, 1GB, 400Mhz(PC3200). One is Ultra, 512mb, 333MHz(PC2700). and a Kingston, 1GB, 333MHz(PC2700). i know your not supose to put them together but when i do the computer reads it as 2.87GB of ram. I'm no math genious, but (3)1GB and (1)512MB, should make 3.5GB.

why does this happen?

10 Answers

  • 1 decade ago
    Favorite Answer

    Various probable reasons :

    - BIOS requires a different slot assignment for the DIMMs in order to properly detect them (try swapping them from slot to slot)

    - One or more of the modiules is defective (try them individually & see what happens)

    - BIOS has a timing incompatability with this particular blend (other than a BIOS update ... no possible solution).


    Philip T

  • 1 decade ago

    I'm surprised that A) your computer even works and B) it read even that much of the RAM. In theory, you're RAM should have a speed which can evenly divide the speed of your motherboard. For example, if your have an 800Mhz bus from your CPU, you need 400Mhz RAM. All of these for "hz" numbers are clock cycles. Ghz, Mhz, are basically like a heart beating. That's how fast the heart of your computer is beating. DDR (double data rate) sends data on the upbeat AND the downbeat. If everything is beating at the same time, everything works great. You, however, are using 2 different speeds. I'm surprised that it reads 2.87 . I would expect it to read all of the 400, or all of the 333.

    Regardless, your computer will only operate at the SLOWEST RAM. you may have 3.5GB of RAM in there, but it's running at the slower 333Mhz so that everything is synchronized. Do you really need 3.5GB of RAM??? 2 is more than enough, and I've never had any problems using just 1. Windows XP only uses 128MB of RAM. After that, the rest can be used to run software. The only people who really need to use that much RAM are people who do a lot of graphic design and rendering.

  • 1 decade ago

    DDR RAM is rated for a certain speed. If you buy RAM rated for 800 MHz, it would be a waste for you to run it at 400 MHz because it is more expensive and is able to run much faster.

    If you put different RAM modules in a computer, it will run them all at the same speed. Some slower RAM is actually able to run faster, but if you do overclock the slower RAM, you run the risk of your RAM crashing or even frying and killing your motherboard, or the RAM itself.

    Most RAM and even hard drives are sold in certain sizes, but due to random errors and defects in the platters or memory chips, may vary from the stated capacity. Most manufacturers even state this in their product catalogs or fine print.

    It is possible that your computer is either not even using one of the modules, or that all of the modules are under capacity, or a combination of these reasons.

    One last thing: YOU DO NOT NEED THAT MUCH RAM unless you are running some serious photo editing software (like Photoshop CS) and 3-D CAD software, and running a server, at the same time. No game out there right now needs more than 2GB at the most. The only benefit you have beyond 2GB of RAM is being able to have several programs running at the same time.

  • 1 decade ago

    for first off, some of your memory might be shared with your video whether its onboard or a card so that could be some that is missing.. I would get a manual or info about your motherboard and see what a proper RAM configuration is for the machine. You cant just go in and throw RAM in any bank and expect it to work.. Make sure the two PNY's are on the same channel. Also dont expect your RAM to be running at 400MHz, its speed is adjusted when slower memory is added. If you have a 32 bit processor, the processor is not able to fully address all 3.2-4 GBs of memory. 2^32 bits max...

  • How do you think about the answers? You can sign in to vote the answer.
  • 1 decade ago

    yup your right, your not really supposed to mix and match memory, but sometimes I do that as well (if its gonna be lying around gathering dust and you can get away with the particular combo you are using, well why not).

    The main problem of mixing memory is the memory will drop to the lowest speed dimms you have, and sometimes you should def. *not* mix different speeds up, like some memory *have* to be installed in pairs, some require the mem banks to be filled in a certain order, others require blanking plates in the empty slots (like rambus rimms), mainly your chipset (amd/intel) and your motherboard (specially the mobo) combo will dictate what you can and cant do.

    When I have mixed memory in the past (and I do try not to make a habit of it) i have *always* found the memory always drops lower to what it should be, most likely because of the mismatch of frequency (speed) or parity. Just be sure you run a burn in test with something like Sisoft Sandra Pro to make sure the memory runs well, and runs okay under load/stress.

  • 4 years ago

    as long as you get the right type of memory stick you can use any size along with the original. However the Bios of the machine must be able to support however much ram will be running on the system.

  • 1 decade ago

    You may have installed as you add up the ram to be 3.5GB but your computer will not read it that way. You can mix any typen with the other as well. If they will fit in the slots they will work.

  • 1 decade ago

    make sure that you plug the largers memory card into the first slot and then nest size in order of size. If you plug it in anyother way then it will not read correctly.

  • Sami V
    Lv 7
    1 decade ago

    Maybe it could turn into a PC5900!

  • 1 decade ago

    i don't think that you should put two different ram together... but maybe it's possible....... my advice:go consult a professional

Still have questions? Get your answers by asking now.