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Types of Memory.

Discussion in 'Hardware' started by sammy, Jul 28, 2004.

  1. sammy

    sammy Guest

    Hi,
    pc supports these types of memory modules and they are all almost equally
    priced.
    What is the catch here (in terms of performance).

    128MB Sdram PC133 4bit
    128MB Sdram PC133 8bit
    128MB Sdram PC133 double sided 16bit.

    Is more (bits) better or less (bits) better ?
    There is also this issue of CL2, CL2.5, CL3. Is this also a case of less
    being better?

    gr
     
    sammy, Jul 28, 2004
    #1
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  2. Hi Sammy,
    The double sided 16 bit is the best and the 4 bit the least best.
    The CL numbers refer to the voltage that the memory uses.
    If you need memory, you can go to www.kingston.com or your
    favorite memory manufacturer and get the part number for what you want
    and e-mail it to us for a quote.

    Hope this helps,
    Silicon Alley Computers
    www.siliconalleycomputers.com
     
    Silicon Alley Computers, Jul 29, 2004
    #2
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  3. sammy

    Zorknob Guest

    Not quite right. CL means CAS Latency and specifies the number of
    clocks that pass from the time the CAS signal is asserted until the
    data is valid on the data bus.

    For DRAM, the address is provided in a two step process, the first
    step is to provide the Row address of the data, followed by the column
    address. The row and column addresses are validated by signals called
    RAS (Row Address Strobe), and CAS (Column Address Strobe). After the
    address is presented, it takes a while for the data to get from the
    memory cells to the data lines. This delay is specified as the number
    of clock cycles from CAS until the data is valid, or CAS Latency.

    Note that 1/2 step latencies (2.5 for example) are only valid for
    DDRAM. SDRAM has only whole step latencies.

    The reason that more data bits per part is better is that you have
    fewer components loading the address lines, so the memory system can
    run faster and use less power.
     
    Zorknob, Jul 29, 2004
    #3
  4. sammy

    Tom Guest

    hi

    SD-RAM has a data-bus width of 64-bits. This is why you can install
    SD-RAM DIMM's in banks of one, as opposed to two like 72-pin SIMMS
    (each SIMM had a bus width of 32-bits, so 2x32bits = 64bits to match
    the width of the CPU's data bus of 64-bits. Every stick of SD-RAM is
    64-bits.

    With reference to the CL values - CL means CAS latency, and it has
    nothing to do with voltages. The CAS latency refers to how often the
    data in the D-RAM is refreshed. A lower value is better as you get
    faster access times when the data in the D-RAM is refreshed faster.
    CAS3 and CAS2 RAM is most common - some SD-RAM is designed to work
    best at CAS3, but will sometimes work on CAS2 but won't be as
    reliable.

    - Tom
     
    Tom, Jul 29, 2004
    #4
  5. Here's a link and and excerpt that addresses your question, amongst
    other things:
    http://www.dewassoc.com/performance/memory/cas_latency.htm

    "CL stands for CAS Latency. It is a programmable register in the SDRAM
    that sets the number of clock cycles between the issuance of the READ
    command and when the data comes out. Smaller number for CL indicates
    faster SDRAM within the same frequency."
     
    Anonymous Jack, Jul 29, 2004
    #5
  6. Ouch,
    Sorry for the misrepresentation. I confused CL with the supply
    voltage when I read the post. That'll teach me for hurrying a reply.
    In my defense, the CL and the supply voltage are often the same.

    Silicon Alley Computers

    Silicon Alley Computers
     
    Silicon Alley Computers, Aug 5, 2004
    #6
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