Hi all,Recently I bought London VFR X and really enjoy the scenery.In the manual there is a list of how the settings best could be.Withe those settings I can fly without getting the OOM.I even can put the scenery complexity slider to max and add autogen for all scenery outisde of London.They suggest to use no Ai Traffic.For making a flight over the city that is no problem.However if you start at another airport without aircraft that is not the way I like it.So I added 50% and 40% Ai Traffic ( MyTraffic 5.2 ) .Now the OOM error appears.I checked the memory while loading and I had 1024mb left ( 4Gb 1800 mhz in the pc ).Normally when being at the desktop and doing nothing I can see that there is around 2500-2800 free memory.I use Vista Ultimate and thought that with SP1 Windows not only recognises 4Gb , but also programs could use memory over 3 Gb.The 3Gb switch I changed to using 4096mb , but no luck.Any suggestions ?

If you are using the 32bit version of Vista then you will still get OOM errors as you cant use more than 3.2Gb of RAM, Microsoft changed the way it reported the amount of RAM you had installed in Vista SP1 so that it would report that you had 4gb installed even though you cant actually use it, they did this just to cut down on the customer support enquiries asking "why can my PC only see 3.2 of my 4gb of RAM". Basically you have to turn your settings down a bit, or get a 64bit OS. I also recommend at least a 512Mb graphics card with VFR London, and preferably a 1Gb card for the best results.

My pc is able to run everthing with most sliders maxed out.Therefor I was thinking that maybe using Vista 64 bit gives me the advantage. As FSX is written as a 32 bit program, would using a 64 bit OS give the memory benefit I need ?

I upgraded to Vista 64bit just because I was sick of getting OOM errors, and I've not seen a single OOM error since changing from XP32bit to Vista 64bit. Nothing else has changed with my PC other than the OS.

The OOM issue with complex aircraft/scenery/level of detail was also my motivation behind moving to Vista 64 for FSX. There are many threads in the hardware forum concerning OOM and the switch to Vista 64.Etienne MartinAVSIM Staff Reviewer

Do all addons work with Vista 64 bit ?And again , does FSX , which is a 32 bit program, benefit from 64 bit ?I mean : a 32 bit program can handle a maximum of x Gb of memory. Will adding extra memory ( by using a 64 bit OS ) be used by it ?As a test :If you have a 64 bit OS and own London VFR X and a addon traffic program try this scenery with 40-50% traffic and scenery complexity set to maximum.On a 32 bit system 3 Gb is not enough to run this and the OOM will appear.Perhaps it will run on a 64 bit system with 4 Gb of memory.

Yes it works in Vista 64 I have all those add-ons and many more besides and it all works fine in Vista 64 and no OOM errors anymore either, although I must admit that I turn UAC off which helps with program compatibility.

I have also changed to Vista 64. I note from the OP first post that there is still a misundertanding of the problem. any 32 bit system can only address 4GB and this is known as Virtual Address Space or VAS. In the first instance it has nothing at all to do with installed ram. It is because 2^32 = 4GBS. Lots of system stuff including the graphics car memeory has to come out of the 4GB VAS leaving the user with about 3GB of useable VAS. (If you have a 1GB grahics card this will be less). The 3GB VAS left has to be shared by the operating system and user programs. So the maximum address space that can be used by a user program is in the 2.5GB to 2.7GB range. It doesn't matter if you have 8GBs RAM any user program can only utilise 2.5-2.7GB of it any RAM over 3GBs will not be mapped and will be ignored. So the short answer is "If you want FSX to use more than 2.5-2.7GB memory the only option is to go to a 64 bit OS".

I will just add that I too have been on Vista 64 bit for a year and all FSX mods work and there are no OOM errors that I have ever seen nor heard of.

The 3Gb switch I changed to using 4096mb , but no luck.Any suggestions ?

You cannot use such a high value with your system...There's a very good reason why Phil Taylor recommended /IncreaseUserVA 2056 as a starting point...