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davidv

3gb Or 4gb In Winxp 32bit ? The 3gb Switch

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Just a question....I bought my system with 4GB of Corsair Dominator DDR2 ram. I switched from Vista to XP and noticed XP only sees 3.25 GB of it. I took the 4th stick out to just run 3GB as I figured I may run into errors and other issues otherwise. Should I keep it at 3gb or put the 4th back in?Also I've seen a lot of references to the "3GB Switch" and so on - I was just wondering if someone could explain the purpose of it, how it works and if it is something I should look at. I've tried the search function but there's so many posts referencing it indirectly I can't find one that actually explains what it does and when you should use it.My system specs are in my signature for reference.

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I have 4 gig of system memory. This is what my 'boot.ini' file has in it.[boot loader]timeout=30default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS[operating systems]multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /NoExecute=OptIn /usepmtimermulti(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional 3GB userva" /fastdetect /NoExecute=OptIn /usepmtimer /3GB /userva=2560Notice I added '/3GB /userva=2560' at the end of the copied line and I added ' 3GB userva' to the copied line's description.When the system boots I have 30 seconds to deside which line to use. I arrow down and press return to use the second line.I left the original line just in case the system has a problem.Something to read up on ---http://technet.microsoft.com/en-us/library/bb124810.aspxhttp://support.microsoft.com/kb/328269

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Windows Xp does only "sees" 3.25, but it does utilize the other .75 for system resources. There's no harm in leaving the ram in.

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nevermind, looks like I already did this at some point and forgot lol. I put the 4th GB back in.

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Just for clarification, all 32 bit operating systems see and utilize a system total of 4GB of memory. This takes into consideration the RAM on your GPU. If you have 4GB of RAM and a 512 MB GPU, XP will report seeing less than 4GB. VISTA reports seeing all of your RAM because Microsoft changed how it reports in one of the service updates. Both operating systems are seeing and utilizing the same amount of your RAM...4GB. In both systems, given this setup, a half gig of RAM is wasted. Regards,Jeff

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From an operational view point, it is generally impossible for a 32bit program to even use 2Gs of physical ram. Generally, the operating system's ram usage forecasting function will OOM the program long before it gets to even 2Gs of physical ram usage. FSX tends to forecast 300-500K higher than the current ram load. FSX will typically OOM at ~ 1.5-1.7G of physical ram loading. It doesn't matter how much ram is installed or how much the operating system sees. To use more ram in this case, a user must run additional programs simultaneously. The 3G switch allows any single 32bit program to use up to 3Gs of physical ram. However again, this ram usage forecasting function will generally OOM the program ~ 2.5G of physical ram. The 64bit op system finally allows a 32bit program to use a full 4Gs of physical. However again, the program will tend to OOM at 3.5Gs of physical ram loads. Good thing too. The op system's gonna need a little bit of physical ram for its own purposes. Remember too, not every 32bit program can use over 2Gs. The program's .exe file must - Also - have a special "switch" set. SP2 set the FSX.exe program switch. FS9's must be set manually. At high(ish) sliders, FSX will always load into the 2nd G of physical ram. Not often, will it load into the 3rd G. That's why the 3G switch tends to work OK. Physical ram loads don't often exceed ~ 2.5G, and thereby challenge the op system's forecasting (and OOMin') 3G barrier. Heavy users (like the LVLD/PMDG crowd) need that 64bit op system to allow the system to load well toward that 3rd G without OOMing. I often see a PMDG flight forcast above 3G. That would OOM even a 3G switched system. That's why it's become almost mandatory for power users to run a 64bit operating system. However very rarely will I see a physical ram load above 3G. In any case, dedicated Vcards don't use system ram. There's some controversy about if Vcard memory is part of the op system's ram forecast number (the OOM stuff). I kinda doubt it. I've been running FS9 lately with an eye toward OOMs and a particular big-dawg airplane FS9 addon. Where memory forecasting runs way ahead of the actual physical ram load in FSX, ram forecasting stays right with physical memory in FS9. Is FS9 simply using zero Vcard memory? I kinda doubt it.

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The 3GB switch has nothing to do with how much physical RAM you have. It has to do with how the memory address space is allocated. This is demonstrated by the description of the variable that is set. "App can handle >2GB address space." The switch can be used just as effectively on a system with 2GB of Ram as 4GB.When set up properly, the 3GB switch should actually be called the 2.5GB switch as setting up the userva to more than 2560 can cause problems, particularly with VISTA and its' higher overhead requirement, compared with XP. Having the switch set up simply lets the sim, with its' complex addons, manage the full 2GB of address space without busting the 2GB process limit imposed by a 32 bit OS. Regards,Jeff

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Well kinda. Op system's switch (3G, 2.5G or whatever) allows the ram forecasting function (or "Address Space" (AS), "Virtual Size" (VS) or "WhatEver" (WE!)) to forecast up to the limit set (3G or 2.5G or whatever). As described, this is not physical ram. Remember, it is the AS number that causes OOMs and it - always - leads actual physical memory ram load. If the AS can go higher, so (then) can the physical ram load before the system OOMs (on the basis of the AS number, 3G, 2.5G or whatever). For instance, if the AS is set to 2.5Gs, then a 32bit program (with its own switch set) could use 2.5Gs of physical memory too. However this will never happen. AS will always lead physical ram usage and OOM the program before the physical memory load reaches this level. Setting this op system switch does not - just - allow a 32bit op system/program to access it default 2Gs limit. It actually - Increases - the Address Space to the limit the user sets in the boot file (3G, 2.5G or whatever). By increasing the AS limit, each program/process running can load more physical ram before AS function OOMs the program. With my Vista 64/4G ram install, I've OOM'd FSX at 4.01G/VS and but at a physical ram load of only 3.3G. (Note: Microsoft's term "Virtual Size" = the term "Address Space" used here. WS Private is physical ram load.)

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Well kinda. Op system's switch (3G, 2.5G or whatever) allows the ram forecasting function (or "Address Space" (AS), "Virtual Size" (VS) or "WhatEver" (WE!)) to forecast up to the limit set (3G or 2.5G or whatever). As described, this is not physical ram. Remember, it is the AS number that causes OOMs and it - always - leads actual physical memory ram load. If the AS can go higher, so (then) can the physical ram load before the system OOMs (on the basis of the AS number, 3G, 2.5G or whatever). For instance, if the AS is set to 2.5Gs, then a 32bit program (with its own switch set) could use 2.5Gs of physical memory too. However this will never happen. AS will always lead physical ram usage and OOM the program before the physical memory load reaches this level. Setting this op system switch does not - just - allow a 32bit op system/program to access it default 2Gs limit. It actually - Increases - the Address Space to the limit the user sets in the boot file (3G, 2.5G or whatever). By increasing the AS limit, each program/process running can load more physical ram before AS function OOMs the program. With my Vista 64/4G ram install, I've OOM'd FSX at 4.01G/VS and but at a physical ram load of only 3.3G. (Note: Microsoft's term "Virtual Size" = the term "Address Space" used here. WS Private is physical ram load.)

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Sorry, I'm not entirely clear here. I use XP Professional 32 bit. I have only 2 gig of ram. I'm not having any trouble with OOM errors. Should I use the 3 gb switch? Can I alleviate the risk of it screwing up my system on the first try? If it does, what are my options? Thanks in advance for these clarifications.GeoffreyQuad 6600 @ 2,4; Asus Striker Extreme; Asus 8800 Ultra; 2 GB DDR 800; Nvidia 500 gig twin drives with Raid; XP Pro 32 bit SP3; FSX Accelleration

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I've never had that error myself either. I don't use the PMDG heavies in FSX though.

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All this is about messing with the op system's kernal. These are core elements of a 32bit op system's most basic function and were NeVer meant to be adjusted. The most progressive pieces of Software are now outgrowing their "House" and need more room. The "family" (ie, software and its operating system) are now in a state of painful transition. These 3G switch and program hi-mem-enable tweaks are just desperation-nonsense-HacKs to get-by in the mean-time. The "fix" is 64bit Programs running on 64bit Op Systems. We have the op system, but no programs, yet. Hopefully Fs11 will be available in 64bit. Then we'll have our new house . . . . That is, until the family outgrows it in another 20 years. And so it goes.Right now, the Best advice is "if it's not broke, don't fix it."

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Sorry, I'm not entirely clear here. I use XP Professional 32 bit. I have only 2 gig of ram. I'm not having any trouble with OOM errors. Should I use the 3 gb switch?
No, the switch is only for those with 4GB of RAM on a 32bit OS (XP or Vista). Do not use it with 2GB of RAM!

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