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32 bit vs 64 bit: How it relates to video cards

Discussion in 'Graphics Cards' started by Mussels, Apr 15, 2009.

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  1. Mussels

    Mussels Moderprator Staff Member

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    I've had to post this too many times so i thought i'd get it out in the correct forum here.

    Minor edit: the below text is a bit fuzzy regarding the 2GB limit per application in 32 bit OS's, and focuses on the 4GB total in the OS. There is a 2GB cap in most programs unless they have a "2GB+ aware" flag set in the program - some games have this already (Sup com: forged alliance, for example) but many others do not, and therefore cant use more than 2GB regardless of how much address space is available - if they try to, they crash (usually mid game)

    Under a 32 bit OS, you have 4GB total (OS) and 2GB per application.

    Under a 64 bit application, 32 bit apps are still capped at 2GB - but if its large address aware (the 2GB+ flag i mention above) then it can use upto 4GB of ram/address space per program.

    Under a 32 bit operating system (XP, vista 32) you have 4GB of address space available. Address space is different to the amount of memory in your PC.

    The reason a 32 bit system can only use 3GB (or 3.25GB, or whatever number you get) of system ram is because it doesnt have enough address space left. Video cards are the most important part of a PC that uses address space.

    If you had 4GB of system ram and a 1GB video card under a 32 bit operating system, each individual program could only use 3GB of that system ram (due to the video card using 1GB of address space) However there is something else most people are NOT aware of.
    Under DirectX 9.0C (and lower) video card ram must be duplicated into system ram. That means if you're running on the highest settings with your new shiny 1GB video card - that 1GB of video memory must be duplicated leaving you with only 2GB left for your game.

    You just went from 4GB to 2GB, only considering a single 1GB video card. Things only get worse in SLI and crossfire.

    Under 64 bit you wouldnt have lost that initial 1GB of ram to the address space, so you'd have 3GB of usable ram, with 1GB used in DX9.0C games. All of a sudden those modern games which border on 1.5-2GB of ram usage are playable, without your system running like a dog.

    Side note: It should be noted that DX10/10.1 does not duplicate video memory into system ram. DX10 actually helps to alleviate this issue, if your system is powerful enough to run games in DX10.

    Side note 2: There is more than just video card ram that affects this. System page file uses address space, as do various parts related to the BIOS (RAID cards, sound cards with onboard ram, etc) - this is why with a 512MB video card your 32 bit OS may report 3.25GB of ram - 256MB was taken away for everything else

    These are the old examples. we've since found out they were a little inaccurate.
    Example configs:
    32 bit
    4GB system ram
    1GB video card

    3GB system ram usable, 2GB left in games once video card ram is duplicated.

    2GB system ram
    1GB video card

    1GB system ram usable, The last 1GB would fight with the video card ram here. If you dont lower texture settings, resolution, and AA you'll get pretty nasty stuttering as you run out of ram.

    4GB system ram
    2x1GB video cards (SLI/crossfire)

    2GB system ram usable, 2GB left in games once video card ram is duplicated.
    (SLI and crossfire only use one video cards ram. Because of how it works both cards ram is in the address space, but only one cards ram is duplicated)

    64 bit
    4GB system ram
    1GB video card

    4GB system ram usable, 3GB left in games once video card ram is duplicated.

    2GB system ram
    1GB video card

    1GB system ram usable, The last 1GB would fight with the video card ram. This kind of PC is the one where people claim vista x64 has no real advantage, or slower due to 64 bit using slightly more ram than 32 bit in windows itself.

    4GB system ram
    2x1GB video cards (SLI/crossfire)

    4GB system ram usable, 3GB left in games once video card ram is duplicated.
    (SLI and crossfire only use one video cards ram. Because of how it works both cards ram is in the address space, but only one cards ram is duplicated)


    32 bit
    4GB system ram
    1GB video card

    3GB system ram usable, 2GB left in games once video card ram is duplicated.
    So that this makes sense: if your game used 512MB of video ram, you'd only have 1.5GB of system ram for the game.
    If its a modern game like modern warfare 2, that game can use 900MB of video ram - hence why the game crashes on many 32 bit systems when there isnt enough ram for game and video ram.


    2GB system ram
    1GB video card

    1GB system ram usable, The last 1GB would fight with the video card ram here. If you dont lower texture settings, resolution, and AA you'll get pretty nasty stuttering as you run out of ram.

    4GB system ram
    2x1GB video cards (SLI/crossfire)

    2GB system ram usable, 2GB left in games once video card ram is duplicated.
    (SLI and crossfire only use one video cards ram. Because ram isnt additive in SLI/Xfire, only one cards ram is duplicated)

    64 bit
    4GB system ram
    1GB video card

    4GB system ram usable, 3GB left in games once video card ram is duplicated.

    2GB system ram
    1GB video card

    1GB system ram usable, The last 1GB would fight with the video card ram. This kind of PC is the one where people claim vista x64 has no real advantage, or slower due to 64 bit using slightly more ram than 32 bit in windows itself.

    4GB system ram
    2x1GB video cards (SLI/crossfire)

    4GB system ram usable, 3GB left in games once video card ram is duplicated.
    (SLI and crossfire only use one video cards ram. Because ram isnt additive in SLI/Xfire, only one cards ram is duplicated)
    3GB system ram usable, 2GB left in games once video card ram is duplicated.

    I was PM'd to edit in a scenario with a system with 8GB+ of ram and 32 bit games. In that situation it would work the same as a 4GB OS, except with more RAM free for background tasks - even if your game is still capped at 4GB, having an extra, 4, 8 or 12GB of ram for your operating system, web browsers, and whatever work you do wont hurt.



    Update:

    http://support.microsoft.com/kb/940105

    This link from microsoft has some good info, and fills a gap i'd missed.
    You do not need to download the file mentioned, as this is already included in vista SP1 (and you should be on SP2 by now!)
    This shows another side to this - 32 bit applications can only have 2GB total for the entire application, regardless of the amount of available ram and system-wide address space. so even if you have 4GB of ram and 3.5GB showing as available, if you've got a 1GB video card in a 32 bit OS you're in for a world of hurt on high settings on modern games.



    Edit: W1zzard has queried the ram duplication, so i managed to find some more links - thanks to Xenos especially.
    http://www.tomshardware.com/news/windows-graphics-ram-desktop-memory,7644.html

    This article is talking about how the aero desktop was moved from DX9 (WDDM1.0) to DX10 (WDD1.1) and they directly mention how the old (DX9) system required a copy of video ram in system ram.
     
    Last edited: Apr 12, 2013
  2. JanJan

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    i know questions i'm about to ask is obvious to many people in here but i'm totally new so bear with me..
    how can you upgrade from a 32bit OS to a 64bit OS?
     
  3. Mussels

    Mussels Moderprator Staff Member

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    You need to format and upgrade. It uses a different install disk.

    For example if you have windows XP and want to go 64 bit, you will need to go buy windows XP 64 bit.
    If you have vista, 32 bit CD keys work on 64 bit - so you can pay shipping and microsoft will send you a 64 bit disk.
     
  4. crazy pyro

    crazy pyro New Member

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    Right, cheers for that Mussels.
     
  5. Darknova

    Darknova

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    Nice information. Thanks Mussels!
     
  6. Ahhzz

    Ahhzz

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    Thanks very much Mussels. Informative. I didn't know that at all. Appreciate it.
     
  7. silkstone

    silkstone

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    Nice Thread Muss, i'' bookmark it and just paste is into all the hundreds of future x64 vs. x86 threads

    Strange - I thought crysis was DX 10? - When i tried it with only 2gb and a 512mb video card it stuttered like hell. Even 3gb wasn't enough to eliviate this problem i had to use 4gb (using vista 64). It seemed like it was still shadowing the video ram even tho its a dx 10 game.'
     
  8. Mussels

    Mussels Moderprator Staff Member

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    crysis is very VERY badly coded for DX10.

    Games like crysis are DX9 ran through an automated converter to DX10... and it doesnt work well. they run like crap.
     
  9. jamupnorth

    jamupnorth New Member

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    If this is true where do i get the 64 bit disk from microsoft ?
     
  10. sneekypeet

    sneekypeet Unpaid Babysitter Staff Member

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    At the store;)
     
  11. jamupnorth

    jamupnorth New Member

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    Cant find that at the store :)
     
  12. HellasVagabond New Member

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    Still the DX10 version of Crysis produces better graphics than the DX9 one.
     
  13. MadClown

    MadClown New Member

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    Great post, very good info.
     
  14. Mussels

    Mussels Moderprator Staff Member

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    yes, but at a massive performance hit.

    In theory, DX10 should be faster than dX9 - lazy coding is the reason it isnt so in most games.
     
  15. FordGT90Concept

    FordGT90Concept "I go fast!1!11!1!"

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    Yup, most DX10 games are still DX9 at heart. DX10 cleaned up a lot of filth that has accumulated in DX9 over the years but, it really doesn't matter because the transistion to purely DX10 or greater (as in no pre-DX10 render path) is still going slow.
     
    Crunching for Team TPU
  16. silkstone

    silkstone

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    Then use google and use the legit key from 32bit vista on the 64bit download.
     
  17. hat

    hat Maximum Overclocker

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    I never knew that vram was copied to system ram like that... that's pretty shitty actually
     
    Crunching for Team TPU
  18. 95Viper

    95Viper

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    Quote:Originally Posted by Mussels

    "You need to format and upgrade. It uses a different install disk.

    For example if you have windows XP and want to go 64 bit, you will need to go buy windows XP 64 bit.
    If you have vista, 32 bit CD keys work on 64 bit - so you can pay shipping and microsoft will send you a 64 bit disk."


    Mussels is correcto mundo!:toast:

    Go here:http://www.microsoft.com/windowsvista/1033/ordermedia/default.mspx

    You have to pay shipping and handling...


    Or for around 349 us dollars, join Technet and use just about all their software, for unlimited evalution...sometimes you can catch it discounted.
     
    Last edited: Apr 18, 2009
  19. jamupnorth

    jamupnorth New Member

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    I have tried this and it does not seem to like the product keys on the back of 2 of my laptops ? any ideas ?:banghead:

    I think the offer has expired
     
    Last edited: Apr 18, 2009
  20. Kweku

    Kweku

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    Nice and informative... I once had a rig with 4GB of ram, but windows only saw 3GB of it, at the time i had a 512MB 8800GT card, so yeah, and funny i was opting to go SLI on that rig.

    Anyways, nice info. Its gonna come in very handy with what I'm building next
     
  21. 95Viper

    95Viper

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    jamupnorth says thanks.
  22. GTX

    GTX New Member

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    wat bout if i have
    2gb of ram and a 512mb vid ?
     
  23. crazy pyro

    crazy pyro New Member

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    Then you aren't affected.
     
  24. silkstone

    silkstone

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    Unless your using dx9 which shadows the ram and so in effect the game would only have 1.5gb minus sstem processes?
     
    IINexusII says thanks.
  25. jamupnorth

    jamupnorth New Member

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    I tried to but they are shut for the weekend , i also have an old copy of vista ultimate with no keys , could i install the 64bit version off that and use the genuine 32 bit keys that i have ?

    One last point can i just upgade from 32it to 64 bit and leave all my files ok or does it have to be a full reinstall , format etc ?

    Sorry if this has nothing to do with graphics cards
     
    Last edited: Apr 18, 2009

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