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FSX, WinXP 4GB...

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After reading Mitches post today, I went out and got another pair of 1GB sticks for my Asus P5B Deluxe, bringing the total onboard memory on my machine to 4GB. This is what I have learned since. These are simplified observations, as I am only picking up anectodal "bits and pieces" and have yet to fully understand the mechanics beneath, but even simple as they are, they are basically true* XP WILL NEVER use more than 4GB, and that includes all the overhead required for PCI devices, system, etc* Most folks who have 4GB will only see approximately 3.O GB in XP. Some see a little more, some a little less. These subtle differences have to do with the chipset you are using* Some mobo's (like mine) support PEB (Process Environment Block) or "memory remap". When this is enabled, apps can use up to 3.0 GB memory, but must be compiled to do so.* Moral of the story...if you install more than 3.0 GB in a Wintel 32 bit system, the last 1.0 GB is wasted as far as application usage goes, unless that application is hard coded to use the 3.0 gb address space (set the LARGEADDRESSAWARE header flag). For me, that is not a problem, as I will use it when I move to Vista sometime next year. XP 64 will also use the full address space.So...back to the original question. Does 3.0 GB work better than 2.0 as Mitch implied in his post? For me it definately does. How do I know? Yesterday benchmarking my system, I took someone's advice and too the bell chopper for a spin at Honnalulu airport. Performance was choppy at best. Now with 4.0 GB (3.0 visible by XP) performance is much improved, and the stutters and choppiness is gone. Like Mitch, I too notice a definate increase in FR, but more importantly, FR is much more stable. Theories? With the extra 1.0 GB usable RAM, the OS now has a full 2.0 GB address space to map to, while at the same time, there is a full 2.0 available for FSX. Wait say you...I thought you said only 3.0 was usable. That's the part I don't yet fully understand, but I've read enough on the net to believe that that last 1.0 gb is being used by device mappings, and other sundry OS tasks. The memory is not wasted "per-see", it's just not usable by the application, but the OS will take advantage of it for standard housekeeping tasks, living up to the claim that XP will use up to 4.0 GB memory. Here is a simplified example I found on the net:Your extra gigabyte of DRAM would get mapped to the higher address. The PCI devices wouldn't.As I mentioned earlier, the PCI bus (in general) is a 32-bit bus. In general, the largest possible value you could assign to the Base Address Register (BAR) of a PCI device is 0xFFFFFFFF (4GB)."Your memory map would be something like this:0 to 3GB: Your first three memory sticks.3GB to 4GB: PCI devices.4GB+: Your remaining DRAM.NOTE: This a gross simplifcation. If someone wants to expand on the reserved parts of the lower 1 megabyte, feel free."These are my annecdotal observations, but I concur with Mitch that 3.0 GB is better than 2.0. Beyond that...nada.YMMV. I'd love if someone more knowledgable came in and disected my post and made fact out of fiction.Cheers,bt

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I have always been under the assumption that memory, while very important to load times and overall smoothness (IE terrain issues, view changes, etc) should have little to no impact on frame rates. This is strictly governed by your CPU's speed, the FSB, and the GPU and fill rate of your graphics card. Maybe FSX is doing something different than other programs with system memory? I just dont see how it can have any noticeable impact on frame rates. Someone enlighten me. If this is truly the case, than Im going to go get more ram. For me with the sim "tweaked" and where I like to fly, Im only using about 800-900mb of my 1G at this point, so Im not seeing any issues as far as I can tell.Hornit

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Giving it a little thought, it makes sense that more Ram improves performance in FSX. I have read several times (I think in the MS web page) that FSX has a default "render to texture" on. This means that as FSX textures are more detailed than FS9, then a cfg that would leave texture loading behind would produce bad blurries. MS then created FSX so that a lot of system resources are dedicated to load textures, including the CPU. This is one of the reasons why FSX has so bad performance in most systems (including mine). Then if you add RAM, you increase the space where textures are kept for use once you run FSX, thus requiring less CPU usage as textures are already available in the RAM.Please someone correct me if I am totally wrong.Leo

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Render to Texture has nothing to do with the detail level of textures, it has to do with how the sim engine draws certain things like the instrument panel and compressed DXT textures.

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