Windows 7 is really good at using its RAM so some good quality 4GB RAM would probably be better than some rubbish 8GB RAM for the use in FSX.

Oh is that so, then I should also install Acceleration. I currently only have sp1 and sp2 .

Acceleration includes SP2.

Observations: My system has a 64 bit o/s and 4 gigs of RAM. At idle with O/S, processes and F-Secure running, it uses around 1 gig. With FSX (SP2) running, I've never seen it use more than around 2.6 gigs. IAN

Acceleration includes SP2.

okie I didn't know that but I went ahead and installed Acceleration.

EDIT: Looks like I was a bit wrong. In a 64-bit OS, 32-bit programs can use 4Gig RAM with the /3gig switch set. In a 32-bit OS, they can only use 3Gig. Learn something new everyday!

The /3Gb switch isn't applicable to any versions of 64-bit Windows. The IMAGE_FILE_LARGE_ADDRESS_AWARE flag needs to be set in the .exe file of a 32-bit application to access upto 4Gb.

But a 64-bit OS can access 2^64 bytes, which is a really large number I can't remember :) .

Windows limits the physical memory to a lot less than the theoretical 2^64b Windows 7 Home Basic 8 GbWindows Home Premium 16 GbWindows Professional and above 192Gb

How did they find a limit of 192GB. They can't have actually tested it.

How did they find a limit of 192GB. They can't have actually tested it.

But they made it. So they set the limit

How did they find a limit of 192GB. They can't have actually tested it.

I'm fairly confident that they did build a system with that much memory for testing purposes.

How did they find a limit of 192GB. They can't have actually tested it.

it's a software limit

Observations: My system has a 64 bit o/s and 4 gigs of RAM. At idle with O/S, processes and F-Secure running, it uses around 1 gig. With FSX (SP2) running, I've never seen it use more than around 2.6 gigs. IAN

Hi, The 4 GB ceiling we are talking about here is Virtual Memory. Not to be confused with physical memory. And applies to 32 bit applications. Every 32 Bit process you start on the machine (fsx.exe is one of them) will have its own 4 GB address space. Half of it, or a fourth (depending on the 3GB switch) will be reserved for system dlls, drivers etc… Windows only commits small amounts of physical RAM to processes as needed. The benefit of having more physical RAM, is that the OS will not need to use the swap file often (slow because it involves hard drive access). That’s what it would do if you open another memory hungry application like Photoshop. Because fsx.exe is a 32 Bit app, even if Windows wanted to be very nice and committed all its memory to it, the simulator would not be able to use more than 4 GB Geraldhttp://www.multicrewxp.com

The /3Gb switch isn't applicable to any versions of 64-bit Windows. The IMAGE_FILE_LARGE_ADDRESS_AWARE flag needs to be set in the .exe file of a 32-bit application to access upto 4Gb.

Yup, you're right. I found this page that explains the differences. Didn't know the differences with 64-bit OS's. My 64-bit knowledge is pretty thin. http://msdn.microsoft.com/en-us/library/aa366778.aspx#memory_limits

Windows limits the physical memory to a lot less than the theoretical 2^64b Windows 7 Home Basic 8 GbWindows Home Premium 16 GbWindows Professional and above 192Gb

Well, that is the windows limit, but not the physical limit. A 64-bit OS could be done that could address all 2^64 (is that like 2000 terabytes or something?). Microsoft artificially reduces the amount so people have to pay more money for the more expensive windows versions

What on earth could you do in FSX to use more than 2 GB ram? Seriously. I've only reached the upper 1's on a few occasions (with the exception of errors). With a PMDG aircraft running, UT2, ASE, REX, and a bunch of addon scenery, I don't even get close to 2.

Concorde-X w/ high res textures, UT2, ASE, REX hi-def clouds, UTX, GEX, FSDT KJFK, and about 3 hours of flying was enough to give me an OOM error with Windows 7 64 and 6GB of memory in my machine.

Concorde-X w/ high res textures, UT2, ASE, REX hi-def clouds, UTX, GEX, FSDT KJFK, and about 3 hours of flying was enough to give me an OOM error with Windows 7 64 and 6GB of memory in my machine.

OOMs have nothing to do with physical ram. Its all to do with the virtual address space.

OOMs have nothing to do with physical ram. Its all to do with the virtual address space.

I realize this, I was stating a situation where I was able to get FSX to use up more than 2GB of memory and I mentioned the other part to reaffirm to others that a 64 bit OS only decreases, not eliminates the possibility of an OOM with FSX.

I realize this, I was stating a situation where I was able to get FSX to use up more than 2GB of memory and I mentioned the other part to reaffirm to others that a 64 bit OS only decreases, not eliminates the possibility of an OOM with FSX.

but it doesn't matter if you have 1GB of Ram or 1TB of ram. OOMs have nothing to do with RAM Ahhh sorry. See what you're saying now