GA-8VM800PMD-775-RH 1gb + 512mb = 1gb ????

Discussion in 'Gigabyte' started by \A_Michigan_User\, Jun 6, 2009.

  1. GA-8VM800PMD-775-RH

    I'm trying to mix a 1gb stick, with a 512mb stick. But I only get a total
    of 1gb, instead of 1.5gb, as expected.

    Can't find anything about "all sticks must be the same size" on the Gigabyte

    Same problem with BIOS version F5... and BIOS F6.
    (I also tried swapping the stick positions.)

    Any idea on how to get 1.5gb total?

    I really can't afford to keep buying more and more memory... and throwing
    existing memory in the garbage.
    I *ONLY* want/need 1.5gb total.

    Do I need to change any BIOS settings? Move any jumper pins?

    (I'm using Windows-XP with all the latest updates.)

    \A_Michigan_User\, Jun 6, 2009
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  2. \A_Michigan_User\

    Paul Guest

    Hardware is documented to different degrees, and it is harder to
    give advice in some cases, than in others.

    I got lucky this time, because I see a note on the Gigabyte specification page.
    It says:

    "Note2: Use of a Double-Sided memory module (the single chip is 512 Mbit)
    is required if you wish to install a 1 GB memory module."

    That sounds like they are recommending the following configuration.

    (16) 64Mx8 chips (the chip density is 512 megabits each)

    It is also possible for a DIMM maker, to use 1024 megabit chips. Gigabyte
    is warning that this configuration would only be half-recognized.

    ( 8) 128Mx8 chips (the chip density is 1024 megabits each)

    The addresses sent to chips, are multiplexed. There is a Row address and
    a Column address, and they access the 128 meg address space. Row*Column must
    have enough bits, to access 128 million locations. Gigabyte is hinting, that
    there aren't enough Row*Column bits, to access into 128 meg addresses, but
    there are enough for 64 meg addresses. If the hardware can only access 64
    out of 128 million locations, the RAM will be half-detected.
    512MB + (1/2 * 1024MB) = 1024MB total

    My guess is, your 1GB module is single sided ? It should be double
    sided, with 16 chips. I'm basing my answer, on that single sentence
    on the Gigabyte site. (I do not expect to find documentation anywhere
    from VIA, the chipset maker, on this matter. Intel, on the other hand,
    has better documentation for their chipsets, which you can download.)

    If you get your memory here (or buy this part number from some
    retailer), you should get the correct formulation. In general, as
    a consumer, you don't normally get a say as to how many chips
    are used - only a few makers provide detailed info on their products.

    A single 1GB stick is $13 here. I don't know what shipping would be.
    At this price, you could buy two.

    If I look on the Kingston site, this is as close as I can get to your model number.

    "This system is limited to double-sided 16 chip DIMMs using 512Mbit (64Mx8) DRAM.
    Kingston may ship single-sided 8 chip version DIMMs which are not compatible
    with this board."

    Note that they warn that they may accidentally ship the wrong product,
    if you order a 1GB stick, since their supplier could provide an 8 chip or
    a 16 chip module. Therefore, they chose not to sell a 1GB module in
    this case! That is why that size is missing from their listing.
    Kingston knows the board can take a 1GB stick, but their product
    formulations are not precise enough in this case, to avoid a potential problem.

    So that means, in this case, I'd "gamble" on the Crucial product, because
    they seem to have their act together.

    Even if you shop in person (i.e. went to the Best Buy and had a look at
    their modules), products have enough packaging material around them,
    you can't always tell what chip configuration is present. So no matter
    where you buy this from, or how you do it, there will be some degree of
    risk. Not all VIA chipsets are like this - I have a VIA chipset on my
    motherboard, and it takes 1GB or 2GB sticks. So if I happened to pop in
    an 8 chip, 1GB module, it would work fully.

    Paul, Jun 7, 2009
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  3. \A_Michigan_User\, Jun 7, 2009
  4. I'm also finding that very few stores tell you the "actual number of chips".
    (Why is that info missing? That's apparently extremely important.)

    I apparently need "16 chips".

    If a 1gb stick says "128m x 64" can I be certain that it will have 16 chips?
    \A_Michigan_User\, Jun 7, 2009
  5. \A_Michigan_User\

    Paul Guest

    That is the problem. The 128m x 64 is actually meaningless.
    It is a "window dressing" that does not help customers.
    It is intended to make the advert look technical.


    When I looked at your Kingston item on Newegg, then looked
    at the picture, I see the back of the module has no chips.
    So that one is an 8 chip module. An 8 chip 1GB module,
    on that motherboard, will only be half-detected.

    (No chips on back of module)$S640W$

    Buy the Crucial one instead. You can buy it straight from
    Crucial, as they're more likely to help you if there is a
    problem with the product. The Newegg picture, did not remove
    the module from the packaging, so we can't look at the back
    of it. But if Crucial says it works, then it works.

    Paul, Jun 7, 2009
  6. Paul,

    Maybe it would help if I understood the math instead.

    128m x 64... in order to get 1gb... wouldn't it *HAVE TO BE* 16 chips?

    I thought 128m x 64 was the memory available in each chip.

    I've already bought my "wrong" memory from NewEgg... so (if they allow me to
    exchange it)...
    I'd like to buy the "correct" stuff also from NewEgg.

    I really hate to shop by "what the picture might look like"... but I guess
    I'll have to in this case.

    I was *SO* careful to try and buy the right stuff:
    1gb (all on 1 stick, not 2)
    Avoid laptop memory
    Not dual-channel
    Not ECC
    Big name manufacturer
    Big name store
    Low price
    Free shipping
    I even made sure it was 1.8 volt

    Results? The wrong memory anyway.

    \A_Michigan_User\, Jun 7, 2009
  7. \A_Michigan_User\

    Paul Guest

    The thing is, *you* were careful, but the manufacturers were not. They're the
    ones getting the "epic fail" here.

    I guess I didn't explain the size very well. The 128m x 64 is a "total array"
    size for the entire DIMM. It means the module is 128 million locations deep
    by 64 bits wide. 64 bits is equal to 8 bytes. 128M * 8 bytes = 1GB. In effect
    it says the module has a total of 1GB of storage space.

    Several generations of memory modules have been 64 bits wide. There isn't a
    choice in the matter. They're all going to be 64 bits wide. *Every* advert
    will have 64 for the second number.

    Since 1GB = 128m x 64bits, we can work out that number without ever
    looking at the module. Say, for example, you had a 2GB module. Without
    seeing any chips, I can tell you the advert will say "256m x 64". You
    haven't learned a damn thing, except how to divide 2GB by 64. So the
    "256m x 64" is as meaningful as saying "2GB". In effect, the advertisement
    has stated the module capacity *twice* in the same ad, by saying both
    "256m x 64" and "2GB".

    The numbers I'm interested in, are "internal" numbers.

    (16) 64Mx8 chips (the chip density is 512 megabits each)
    ( 8) 128Mx8 chips (the chip density is 1024 megabits each)

    In the case of the first module, they're arranged like this. This is a two rank
    or "2R" module. I think that is one of the terms JEDEC might use for it. Only
    one rank is "active" or drives the bus, at a time. There is a chip select
    for each rank, and that is how the motherboard gets their attention. Eight
    chips would be on one side of the module, and eight more on the back.

    +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+
    | 64mx8 | | 64mx8 | | 64mx8 | | 64mx8 | | 64mx8 | | 64mx8 | | 64mx8 | | 64mx8 |
    +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+
    | | | | | | | |
    / 8 / 8 / 8 / 8 / 8 / 8 / 8 / 8
    | | | | | | | |
    +----------+--- data-----bus-------on----------edge------connector------------
    | | | | | | | |
    / 8 / 8 / 8 / 8 / 8 / 8 / 8 / 8
    | | | | | | | |
    +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+
    | 64mx8 | | 64mx8 | | 64mx8 | | 64mx8 | | 64mx8 | | 64mx8 | | 64mx8 | | 64mx8 |
    +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+

    The other module design (the one Kingston said they might mix up accidentally, if they
    had chosen to sell you a module), looks like this. This module is only half detected
    on your motherboard.

    +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+
    | 128mx8 | | 128mx8 | | 128mx8 | | 128mx8 | | 128mx8 | | 128mx8 | | 128mx8 | | 128mx8 |
    +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+
    | | | | | | | |
    / 8 / 8 / 8 / 8 / 8 / 8 / 8 / 8
    | | | | | | | |
    +----------+--- data-----bus-------on----------edge------connector------------

    Both modules have an "external dimension" of 128m x 64, but that number doesn't tell
    you how they're arranged internally, or the size of each chip. There are other
    ways I can make modules if I want. Here is another module. (Chips are available
    in 4, 8, 16, and even some 32 bit wide ones. Plenty of choices.)

    +--------+ +--------+ +--------+ +--------+
    | 64mx16 | | 64mx16 | | 64mx16 | | 64mx16 |
    +--------+ +--------+ +--------+ +--------+
    | | | |
    / 16 / 16 / 16 / 16
    | | | |
    +----------+--- data-----bus-----+
    | | | |
    / 16 / 16 / 16 / 16
    | | | |
    +--------+ +--------+ +--------+ +--------+
    | 64mx16 | | 64mx16 | | 64mx16 | | 64mx16 |
    +--------+ +--------+ +--------+ +--------+

    Again, the advert for that module says "128m x 64". It doesn't even hint that 16 bit
    wide chips are being used, or any other internal detail you might want to know.

    So there is plenty missing from the description.

    The industry has had plenty of time to fix this, but they choose not to.
    This is even a problem for people with ten year old 440BX motherboards,
    buying PC133 modules. There are two ways to make 256MB SDRAM modules,
    and one is "half-detected". So the problem has existed for ten years,
    and customers are still getting the wrong memory.

    Paul, Jun 7, 2009
  8. \A_Michigan_User\, Jun 7, 2009
  9. \A_Michigan_User\

    Paul Guest

    As long as either company treats you right, if there is a problem
    with the product, then go with the cheaper one. Make sure you
    know what the Newegg return policy is - how many days you have to
    test it and so on.

    After installing the RAM, your first boot should be a copy of memtest86+.
    Run two passes, to prove the memory isn't total crap.

    Keep the old memory around, just in case. If you ever have a problem,
    and need to verify the computer still works, you can plug in that
    512MB for a test. You don't have to immediately sell it on Ebay (if
    you could - the demand for it might not be there).

    Paul, Jun 7, 2009
  10. Wow, this just gets stranger and stranger.

    Now even with the "correct" memory (as suggested by my 2x1gb
    are only seen as a total of 1gb.... instead of 2gb.

    (My original memory worked fine. 2x512mb sticks.)

    Memory: CT2KIT12864AA667 (matched set of 2 sticks @ 1gb each)
    Motherboard: Gigabyte GA-8VM800PMD-775-RH
    BIOS: F6 (the very latest)
    OS: Windows XP Pro (with all the latest patches)

    What else could be causing this odd problem?

    \A_Michigan_User\, Jun 13, 2009
  11. \A_Michigan_User\

    Paul Guest

    OK, do the memory modules have heat spreaders on them ? Doesn't look like
    it here. The side without the stickers may be visible.

    If they don't, you can read off the numbers on the top of the memory chip.
    You can see an example here. There may be multiple lines of text. (This
    is graphics memory, but it is the same idea.)

    The expectation was, these would be 16 chip modules. Are they 16 chip ?
    With both the part number and the chip count, it may be possible to
    identify what the module is.

    Crucial modules sometimes have a Micron sticker on them as well.
    (Dual stickered modules.) Crucial doesn't have data sheets for
    all their memory, but the Micron sticker can be looked up on . Back when some of the Newegg pictures were higher
    resolution, I could look up the modules before anyone bought

    Paul, Jun 13, 2009
  12. Heat Spreaders? No.
    Stickers? Yes

    They have 8 chips a stick. All 8 chips on 1 side of the stick.

    I can't easily get to the stickers... to read the info... because it's in
    the computer now.
    (I've opened the case SO many times... I'm really not looking forward to
    doing this all over again.) ASSURED me those were DEFINITELY the correct memory modules for
    my motherboard.

    I can't just keep buying "random (non-refundable) guesses" like this.
    Very frustrating. Very expensive.

    Looks my choices are:
    Either I keep buying the wrong memory (my fault).
    I keep buying the wrong memory (the seller's fault).
    I keep buying "unknown" memory because no one lists simple info like:
    "How... Many... Chips... Are... On... These?"
    \A_Michigan_User\, Jun 13, 2009
  13. \A_Michigan_User\

    Paul Guest

    Crucial has a "chat" thing on their web page. Tell them the board
    needs a 16 chip module, and to check the particulars in their
    database. If they need help, tell them to search using the
    Kingston search engine, where Kingston won't sell a 1GB
    module for that motherboard, for fear of getting it wrong.
    It would appear that Crucial has the same "lack of control"
    in the inventory department.

    It is possible to tell what you're going to get. Have a look
    at the Micron sticker. There may be a "-8" somewhere in the
    part number. The "-8" or "-8T" means an eight chip module.
    A "-16T" would be a sixteen chip module. But the problem is,
    I've never been able to find a translation table from
    "Crucial sticker" to "Micron sticker", in order to verify
    the composition. The Micron sticker likely has tighter
    controls over construction. If there is no Micron sticker,
    it means Crucial got the module for resale elsewhere.
    (Micron is their parent company, but due to various problems
    they've had, and the economics, you may also see Samsung
    chips in some cases.)

    I don't know all their policies, so I don't know what they'll do next.
    Most companies will not cross-ship, so you get an RMA number,
    ship the product back (with the RMA number printed in large
    letters on the parcel), and then they'll forward the right stuff
    (maybe). Very few companies ship the replacement product in

    As far as I'm concerned, based on the evidence I can find, the
    product should be

    (16) 64Mx8 chips

    Paul, Jun 13, 2009
  14. As far as I'm concerned, based on the evidence I can find, the
    That sounds like what I need.
    Would that also be called "low density chips"?

    But translating that into "an actual part number" that's definitely
    correct... is nearly impossible.

    When I try to buy based on "pictures" I'm told "pictures don't alway
    represent the actual product".

    Where can I find an online store that definitely states "16 chips" and gives
    a Kingston or Crucial or Micron part number?
    (Or any major company.)

    From that part number... I should be able to "shop around" and find the best

    (I'm finding $50 price differences for exactly the same memory sticks.)
    \A_Michigan_User\, Jun 13, 2009
  15. \A_Michigan_User\

    Paul Guest

    Well, now you're depending on the "satisfaction guaranteed"
    response of your vendor. If you paid with a credit card, you
    have an overall dispute resolution mechanism you can employ.
    If you paid cash, you have less leverage.

    I don't know how easy it is to get "Micron" branded modules
    as such. Maybe they only wholesale them ? I've never really

    This would be a Micron part number.

    The datasheet covers more than one module. In table 4
    the "base device" on the 1GB module, is MT47H64M8. The 64M8 implies
    an 8 bit wide device. 8 chips per rank (to make a 64 bit wide array).
    2 ranks per module. 16 chips total. I wanted to check that, as
    a double check that the diagram in Fig. 2 and Fig. 3 is hot a

    So if there was a Micron sticker on your module, indicating MT16HTF12864AY-667.
    it would have been the right RAM.

    The thing is, Crucial is the retail arm, and has less precision in
    what the sell (no datasheets). Micron does have the precision
    (like Kingston, providing datasheets for at least some of the product).


    Right now, what matters, is beating on Crucial for what you paid for.
    All the rest is noise. Keep at them.

    Paul, Jun 13, 2009
  16. I haven't tried "only 1"... but I've tried "swapping them"... as well as "my
    2x512mb sticks have
    worked flawlessly for years".

    I don't know how many other motherboards have this little-known "feature"...
    but mine has:
    I just need to find someone that sells that... and can *CONFIRM* that it
    definitely has
    16 chips.

    So far, salespeople have been telling me:
    "I don't know"
    "It doesn't really matter"
    "I've never heard of that"

    It *DEFINITELY* matters if you have the Gigabyte GA-8VM800PMD-775-RH
    \A_Michigan_User\, Jun 14, 2009
  17. \A_Michigan_User\, Jun 14, 2009
  18. \A_Michigan_User\

    Paul Guest

    Reading the customer reviews, the third review down right now, is a
    person in your exact position. They bought the product, believing
    the datasheet, as a "low density" module, and what was delivered
    was an 8 chip module.

    "Low density not guaranteed" 5/28/2009 3:04:35 PM

    Cons: I ordered this for a system that requires low density memory
    modules. The product images show a low density module, and I
    found a datasheet for this model that describes a low density
    module, but what I received is a high density module with the
    same model number. So I can't use it. So. If you need a low
    density module you're taking a chance with this model.

    You're going to have to work with someone, to get a 16 chip module.
    That may mean, if using Crucial, talk to one of their customer
    service agents, and make sure the order is marked as "low density",
    so that the right module is sent.

    I'm surprised Kingston released a datasheet like that, and then
    produced a mismatched module. I've always relied on their
    datasheets in the past. I guess they're now meaningless...

    Paul, Jun 14, 2009
  19. \A_Michigan_User\

    andy Guest

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