>>>For example, a video card with 512MB of onboard RAM will>>consume 512MB of the available operating system's slice of>>VAS, so robbing too much from the OS's slice can cause a lot>>of problems. As always, this is a balancing act...>>>>So, the question is: what is the minimal slice of VAS that the>operating system comfortably needs? WinXP 32-bit here. >>>or whatever size you wish, keeping in mind the 1MB>contiguous>>limit of FSX. In such a case, using any number that isn't a>>multiple of 512MB simply doesn't make much sense...>>How do you infer this? Pls read again and explain. I don't see>the logical connection. I know I'm missing something. :)Dirk, the 512MB I cited in the above example was directed at the specific case of using a video card with 512MB memory.In fact, you can fine tune the parameter to nearly any increment you like, provided it is a power^2 value. ;)

Yikes! Somehow during the migration of the forums to this new platform, the original post in this thread has now become #26!This is the orginal post in this thread:http://forums1.avsim.net/index.php?showtopic=65741&st=26See this Wiki Article also:OOM Errorhttp://forums.flightsim.com/fswiki/index.php/OOM_Error

>If you dont see any OOM errors on 4GB, don

Agreed BillBut we are talking about FSX and FS9 here, not multitasking, and I know what you mean.and at the same time if the value needs tweaking because of system/application requirements that should become apparent to the user from seeing how the system normally ran in the past without the edit and memory installed There is no way I can think of for the typical user to calculate that value unless they understand everything there is to know about the needs of the installed software and their use of it so the baseline is general to get the ball rolling, and in that my statement was generalMost wont have any need to change from there unless something dictates otherwise like Dirks FS9 crash.. etc

>I once heard that that the boot.ini on Windows XP Home would>not accept this line. Is that true?My research has so far indicated that while at one time this may have been the case, with all SP2 and all Updates current, it is now working. In any event, here is a method that will allow you to try it in a non-destructive method. It will allow you to choose at boot time which environment you want to load:a) Access the boot.ini file by opening the System Properties dialog on "My Computer". Under the Advanced tab and Startup and Recovery press Settings. In the startup and recovery dialog press the edit button. This should open a text file with something close to the following content: [boot loader] timeout=30 default=multi(0)disk(0)rdisk(0)partition(1)WINDOWS [operating systems] multi(0)disk(0)rdisk(0)partition(1)WINDOWS="Microsoft Windows XP Home Edition" /fastdetect /noexecute=optin :( Were are going to modify it and make a failsafe so that if the mod doesn't work we can go back to the original setting: Copy the last line and add /3GB to the end of it (make sure you spell it right). Between the parentheses type 3GB at the end so you'll be able to recognize it when XP restarts. Also if you don't have noexecute=optin add that too. The whole thing will look like this [boot loader] timeout=30 default=multi(0)disk(0)rdisk(0)partition(1)WINDOWS [operating systems] multi(0)disk(0)rdisk(0)partition(1)WINDOWS="Microsoft Windows XP Home Edition" /fastdetect /noexecute=optin multi(0)disk(0)rdisk(0)partition(1)WINDOWS="Microsoft Windows XP Home Edition 3GB" /fastdetect /noexecute=optin /3GB c) Save the file and restart the machine. Now you will have 2 choices when booting. Pick the '3GB'. If it crashes or you experience any other problems go back to the first option. Later try adding the userva=nnn switch to the last line of boot.ini and save. This is how the last line would look: multi(0)disk(0)rdisk(0)partition(1)WINDOWS="Microsoft Windows XP Home Edition 3GB" /fastdetect /noexecute=optin /3GB /userva=2560 Also check System Properties and make sure that under the General tab it say Physical Address Extension at the bottom.

Very Interesting post that brings up a question.Is there any way to limit the amount of memory the video card uses on a temp basis? I have an ATI 2900XT with 1gig of video memory. Hindsight being what is it, probably not the best choice for trying to run FSX. And it is clearly evident in that I have BSODs referencing ATI dlls when I tried w/o a USERVA switch.Hate the thought of giving up a less than six month old card . . .Joe Lorenc

Doesn't SP2 automatically address this issue for Vista? Thanks...

>Dirk, the 512MB I cited in the above example was directed at>the specific case of using a video card with 512MB>memory.>>In fact, you can fine tune the parameter to nearly any>increment you like, provided it is a power^2 value. ;)>Thanks, Bill. It does make sense for me finally. But what am I gonna do with my 1024Mb video card? Buy a new one with 512Mb onboard? I know that /Userva=2048 is too little (getting OOMs in FS9) and /Userva=3072 would be too much (I'm thinking in 1024Mb chunks here per your explanation). For what it matters I got 4GB of RAM, but I understand it is not relevant. Nick_N assured me it should not be a problem, but your post leaves questions. What if I'm loosing on the performance with this 1Gb card? No one has answered yet how much VAS the system needed to run comfortably? What are your thoughts on this?Many thanks.

And btw, is /3G /Userva=2048 setting + modified FS9.exe (over 2Gb aware) situation the same like non-3Gb boot and non-modified FS9.exe for the system running FS9? I'm thinking about this 2048 value. I'll try /userva=2048 and see if it cures my OOMs. For me it will be important since I'll be able to keep my 1GB RAM card. I calculate it this way: 2048Mb for FS9.exe, 1Gb for my card and 1Gb for the system. Does my estimate look right? :)

Bill,Thanks, I will give that a go.

>Doesn't SP2 automatically address this issue for Vista?>Thanks...The only thing SP2 did was mark the fsx.exe file with the /LARGEADDRESSAWARE flag. It's still up to the user to enable the /3GB switch and specify (if desired) the precise amount of UserVA to use.

>For what it matters>I got 4GB of RAM, but I understand it is not relevant. Nick_N>assured me it should not be a problem, but your post leaves>questions. What if I'm loosing on the performance with this>1Gb card? No one has answered yet how much VAS the system>needed to run comfortably? What are your thoughts on this?Remember, we are only talking about the allocation of addresses, not physical memory...As long as the total number of addresses needed by the OS and video memory-mapping doesn't exceed what is available in its 'slice' of VAS, the actual data will be spread out amongst the physical memory and virtual memory on the HD. It is the swapping back-and-forth from the HD's virtual memory to physical memory that will cause slower performance in such cases.I should think using /userva=2560 wouldn't be too much.Specifying /userva=2048 would be rather pointless, since that is the default setting of 2GB:2GB anyway! ;)

Bill: Thanks for the quick reply...Can you explain to a real newbie exactly how to enable the switch? What file do I edit and exactly what do I enter? I have 4gb of ram and will be using Vista Ultimate...I will be installing both SP1 and SP2...768mb nvidea 8800 gtx video card...This will be a fresh install of FSX on a new computer...Thanks for your patience...Steve in Kansas

Steve, I think you don't need to change ANYTHING in Vista Ultimate 64-bit. Is your VU 64-bit?

>It is the swapping back-and-forth from the HD's virtual memory>to physical memory that will cause slower performance in such>cases.>I should think using /userva=2560 wouldn't be too much.>>Specifying /userva=2048 would be rather pointless, since that>is the default setting of 2GB:2GB anyway! ;)Thanks, Bill. No space for 1Gb video in a 32-bit OS is my inference. I think I've seen some unusual back-and-forth swapping, that cought my eye messing with the settings recently.

No, it is 32 bit...Thanks