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Thread: What DDR2 is this?

  1. #1
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    Default What DDR2 is this?

    A guy on my local site is selling these 4GB modules:




    I'm confused because they look like registered modules (buffer chip in the middle), but the P designation implies un-registered, and that part number comes up as unreg in a few places when searching around. Also, the notch key is the same as standard DDR2 as far as I can tell. Which is it? Is that "buffer" chip something else, or just sitting dormant?

    My board (nForce 590 / socket AM2) can take ECC unregistered/unbuffered. I'm guessing these aren't what I want, but if they are, it'd make my day. Advice needed.

  2. #2
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    This is what Amazon says:

    Mfr Part Number: M393T5160QZA-CE6
    Type: DDR2
    Capacity: 4 GB
    Speed: PC5400 667MHz
    Size & Bit: 512 x 4
    Pins: 240pin
    ECC: Yes
    Registered: Yes
    Chip: Samsung
    Rank: 2
    Chips: 18
    CL 5
    RoHS Compliant

  3. #3
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    ^^ thanks; that confirms what I thought it was, but why is it designated "5300P" (parity) rather than "R" (registered)? Am I missing something or did they just mark it wrong?

    Rant: ECC registered is worth peanuts everywhere, while non-ECC unregistered goes for about double the price, especially for 4GB sticks. ECC unregistered is apparently made of unicorn teeth. Why is the specific one of something I want, always the expensive one??
    Last edited by xjas; October 23rd, 2018 at 09:00 PM.

  4. #4

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    Quote Originally Posted by xjas View Post
    Rant: ECC registered is worth peanuts everywhere, while non-ECC unregistered goes for about double the price, especially for 4GB sticks. ECC unregistered is apparently made of unicorn teeth. Why is the specific one of something I want, always the expensive one??
    I suspect that's for older stuff. Server operators can't afford to run something as small as 4 GB so it's worthless to them, and desktop boards generally can't use it. So you're complaining about something useless being cheaper than something useful.
    WANTED: Cardinal 2450MNP modem.

  5. #5
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    P means parity (ECC)
    F or FB means fully buffered
    R means registered
    U means unbuffered
    What I collect: 68K/Early PPC Mac, DOS/Win 3.1 era machines, Amiga/ST, C64/128
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  6. #6
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    ^^ which is why I'm confused; what seem to be Registered (R) DIMMs are marked Parity (P). I'm wondering if they did something like built all modules the same, but changed the firmware to make them registered or unregistered. Does that even make sense?

  7. #7
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    Registered RAM has an extra chip between the RAM chips and the memory controller to make things more stable with more RAM DIMMs (also adds a wait state). You can see the extra chip in the middle of the DIMMs.
    If the RAM chips are grouped in 9's you have ECC, 8 means non ECC.
    You can have ECC ram that is (R)egistered (extra chip) or (U)nbuffered without the extra controller chip.

    FB RAM has the notch in a different location because the modules are different then other RAM. FB uses serial interface between the memory controller and RAM buffer, normal DIMMs use a parallel bus architecture. This means FB DIMMs have more wait states and also use more electricity so run hotter.
    What I collect: 68K/Early PPC Mac, DOS/Win 3.1 era machines, Amiga/ST, C64/128
    Nubus/ISA/VLB/MCA/EISA cards of all types
    Boxed apps and games for the above systems
    Analog video capture cards/software and complete systems

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