Ram : buffered / unbuffered ?
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Thread: Ram : buffered / unbuffered ?

  1. #1
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    Ram : buffered / unbuffered ?

    What is the difference?

    the reason i am asking is somebody said that pc66 ram is buffered and pc100 is not that is why pc100 is not 100% backwards compatible but i have read somewhere it is 100% backwards compatible.

    now i am confused Mike

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    1ghz athlon thunderbird 383mb ram 10gb hdd(dont laugh getting 30gb soon)+ 6.4gb 8x4x32 samsung writer voodoo3 2000 agp.
    icq 82991416

    [This message has been edited by Mike3d (edited 09-25-2001).]

  2. #2
    DrMDJ is offline Virtual PC Specialist!!!
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    Ya know what they say: nothing is 100%. That goes for ram as well.

    The (relatively) short answer to your question is that downward compatibility of PC100 with PC66 memory does not relate to either being buffered or unbuffered (both may or may not be, and it is best not to mix buffered and unbuffered regardless). It has much more to do with the timing specifications of the (in this case) PC100 memory, specifically the CAS timings, and what is programmed in to the SPD (serial presence detect) eprom on the ram module. There are also isues in terms of the DRAM timing configuration in the bios. The end result must be that a match between the timings (not just the bus speed) for all installed modules must be obtainable.

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  3. #3
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    cheers for that but i still dont know what buffered and unbuffered are.

    Thanx always learning Mike

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    1ghz athlon thunderbird 383mb ram 10gb hdd(dont laugh getting 30gb soon)+ 6.4gb 8x4x32 samsung writer voodoo3 2000 agp.
    icq 82991416

  4. #4
    DrMDJ is offline Virtual PC Specialist!!!
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    Sorry, didn't realize that was the question.

    In short, buffered ram has a buffer (chip) on the ram module that provides buffering and interface between the motherboard chipset and the actual memory chips on the ram stick. The purpose is to provide further control of the (electrical) signals and accesses to the individual addresses on the chips, thereby taking some of the load off the memory and address buses.. Unbuffered ram does not have the added buffer and, therefore, the signaling and accesses to memory addresses on the ram stick is completely under the control of the motherboard's memory controller. You can't mix buffered and unbuffered ram in the same system. To use buffered memory the motherboard's memory controller must support it.

    I actually mis-spoke (in hurrying) in my first answer. SDRAM doesn't come in a buffered variety. EDO ram can be buffered (or unbuffered). With SDRAM the modules can be either unbuffered or "registered". Registered is slightly different than buffered. Registered DRAM has an additional register (logic) chip that exerts further control over memory access by introducing a timing delay. The intention is to provide for greater data integrity and syncronization of the data in memory.

    For home systems neither registered or buffered memory is really necessary (assuming first the system will handle it).


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    [This message has been edited by DrMDJ (edited 09-27-2001).]
    Please remember to post back whether your problem is resolved or
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  5. #5
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    Thanx a lot mate now i understand.

    Mike

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    1ghz athlon thunderbird 383mb ram 10gb hdd(dont laugh getting 30gb soon)+ 6.4gb 8x4x32 samsung writer voodoo3 2000 agp.
    icq 82991416

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