Why is there a Ram Maximum?

By LeeLuck
Jan 2, 2010
  1. Hi all, happy new year ;p

    I recently upped my ram on my MB to 4gig for my Windows 7 ultimate to which my pc now states i only have 2.9gig usable ? guess thats the 64bit OS eating at it ? anyway my question is :-

    What determines the maximum ram a MB can handle ?

    Reason i ask is because my dad has an old Imedia which states its maximum is 2 gig but he has 3gig installed and windows recognises it and it runs fine with no issues.

    My ixtreme has two slots and i want to know what would happen if i put 2 x 4gig trips in ? PackBell state 3 gig max but is that because the pc originally came with 32bit vista or is it a MB thing ?

    Hope some one can clarify this for me.


  2. jobeard

    jobeard TS Ambassador Posts: 9,160   +599

    we have Windows-32bit and Windows-64bit systems. 32 vs 64 refers to the size of the word that contains the ADDRESS to a location in memory.
    These addresses are limited to 32bit or 64 bit 'words', eg 2^32 power or 2^64 power.

    2^32 = 2.17 gig, or 2170 meg

    A Win-32 system will therefore be unable to access any addresses greater than that value.

    All this only applies to physical memory; the software accesses virtual memory which can be 2-3x larger.
    Usually the home user sees not improvement using a 64-bit system which have two primary uses:
    1) large mathematic calculations and 2) server systems with high hit rates.
  3. LeeLuck

    LeeLuck TS Member Topic Starter Posts: 58

    Thanks for the tech talk Joe lol a wee bit over my head ;p
    What i did pull from the info was "home user" yes i am a home user and normally i guess 64bit wouldnt benefit normal home use but i use 3D animation programs that utilise 64bit render engines for speed so i guess number 1 from your uses places me.
    However i dont know if you answered my question as your reply, although very appreciated was a wee bit technofied if there is such a word lol

    How does this affect the MB and maximum ram if i have changed the OS to 64bit ?

  4. jobeard

    jobeard TS Ambassador Posts: 9,160   +599

    the 64 bit systems allow MASSIVE ram addresses
    eg 2.17 gig times 2.17 gig

    However, we've been rendering for 2+ decades now and some programs are not 64 bit compatible --- look before you leap :)
  5. LeeLuck

    LeeLuck TS Member Topic Starter Posts: 58

    Mmmmm both my programs (3DsMAX09 and PoserPro) are 64 bit versions, hence the ram update i wish for.

    I am a little confused by your answers as its the maximum ram of the MB i need to know if i can exceed ?

    My MB maker and pc maker both tell me 4 gig is my MB max. but is that because the pc was shipped with Vista 32bit or is it a bios / voltage / cricuit thingy ?

    I know my new 64bit OS can take upto 128 gig but what can my MB take ?
  6. jobeard

    jobeard TS Ambassador Posts: 9,160   +599

    Then why argue? You basically have a 32bit MB with a 64bit OS.
    (ps: the hardware ALWAYS wins any debate)
  7. LeeLuck

    LeeLuck TS Member Topic Starter Posts: 58

    Am not arguing !! i am simply asking what defines a MB's maximum ram to which i still havent had an explanation ?

    I thought these forums where to find things out and learn rather then just take it for granted that it only does what it says on the box ?

    So back to the initial question. What makes it a 32bit MB ? is it bios ? voltage ? build ? can it be changed ?
  8. jobeard

    jobeard TS Ambassador Posts: 9,160   +599

    the memory access BUS is only 32bits wide and a 64bit address will either
    a) be truncated to 32bits (unlikely for security issues)
    b) cause a hardware machine check

    the 64bit OS understands the physical hardware and does not initiate 64 bit operations for your system.

    That's the best I can give you .... good luck
  9. LeeLuck

    LeeLuck TS Member Topic Starter Posts: 58

    OK, so if i were to want to upgrade my Ram past 4 gig i would need a MB that has a memory access BUS of 64bit ?

    So, do i assume that a MB can either be 32bit or 64bit ? and if so does that mean that even though my MB (which you say has a 32BIt BUS) is running W7 64bit, is it actually only running it in 32bit speed ?

    I appreciate you time on this jobeard, im not a tech head as you have gatheredlol i just need to know the basics because if i have these wonderfull 64bit programs and W7 64bit OS is it all a waste cos my MB only allows 32bit ?

    I am sort of nearly there with a decision on my next upgrade lol probably a new custom built PC ;p

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