What do memory organization numbers mean?

JBJB Carlsbad, CA
edited April 2005 in Hardware
Ok guys, here is the deal. I am looking at upgrading my ASUS A7V333(KT333) chipset to 1GB DDR modules. Simple, right? Well, I've been looking at a bunch of memory, and one value is really confusing me. That is the memory organization.

To start off with here is a link to a stick of RAM crucial says will work with my system. here
Their page says it has 128Meg x 64 organization. I emailed them asking what exactly that value means and I got a response of:
The expression 128Megx64 is the module configuration; it identifies a 1GB non-ECC DIMM. It indicates nothing about the chip count and density on the module.
Ok, so this should be easy. Any memory labeled as 128Mx64 should be 1GB DDR modules, right? Well, not quite. I was browsing newegg (they use to list these values with each stick, now you have to go to the manufacturer's web page :grumble: ) and i found this and
this .

Now, these are links to modueles that are 128Mx64 and 64Mx64 so what is the difference? They both have 16 chips, so the MB/chip must be the same. Is it a matter of how the memory cells are structured in the stick? Is there an advantage/disadvantage to either method? Thanks for the help guys!

Comments

  • dodododo Landisville, PA
    edited April 2005
    ok, i think i understand this, but i dont know how well i can explain it.

    I took a look at page 4 of both of the manufacturs links you listed. This is what I see:

    From those diagrams, each module is comprised of 16 chips. On the one, they are 64Mx8 and the other, 128Mx4. These values are in megaBITs, not megaBYTES. That means that both are 1GB total (128Mb*4*16=8196Mb=1024MB, and 64Mb*8*16=8196Mb=1024MB).

    As far as the 128Mx64 and 64Mx64 organization, it could be from the groupings of 4 (horizontally in the diagram - 2 groups on each side of the module) of the chips. You can see that signal DQ is on the order of 64, so that could be it.

    I don't know what the guy from Crucial was talking about.

    ~dodo
  • JBJB Carlsbad, CA
    edited April 2005
    dodo- the megabits definatly makes sense, but im still wondering about the actuall difference between 128Mx4 and 64Mx8, since the block diagrams have the exact same structure and signal paths. The only difference seems to be the marking on their chips? I'll have to look at the spec sheets a little harder and see if i can find the difference. Any other ideas?
  • dodododo Landisville, PA
    edited April 2005
    Radeon_Man wrote:
    dodo- the megabits definatly makes sense, but im still wondering about the actuall difference between 128Mx4 and 64Mx8, since the block diagrams have the exact same structure and signal paths. The only difference seems to be the marking on their chips? I'll have to look at the spec sheets a little harder and see if i can find the difference. Any other ideas?

    I believe the difference would be in the internals of the blocks in those diagrams. A 128Mx4 would contain "banks" of 128M ram bits, using 2 bits to choose which of the 4 banks to access. The 64Mx8 would use 3 bits to select a "bank" from the 8 available. The rest of the memory addressing bits would be used to calculate the placement within a bank.

    ~dodo
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