How FSX works. My understanding of it, or lack there of.

[Solren 1]

Gentlemen;

 

Like many of you I have read with intense interest all the threads here, and else where, concerning the tweaks and inner workings of Microsoft's Flight Simulator X. I think I understand most that I have read, and am sure I've misinterpreted others. I just wondering how well I do understand it. So here goes. This is my understanding of how FSX works.. Please correct or comment.

 

For example; in FSX in itself:

1. FSX will behave differently, performance wise, from one platform to another regardless of how similar they may be. In other words, what works for me may or may not work for you. I think that most of us do believe this; I do.
   

1. FSX is extremely CPU intensive; not only from calculating the simulation itself, but more importantly, from rendering the graphics. FSX originally was not designed with today’s graphic cards in mind. Scratch that last one. FSX was designed before today’s advanced graphic cards were widely available. I'm pretty sure this is a fact. (As a side bar does anyone know if FSX uses look-up tables to determine flight characteristics or does it calculate flight characteristics on the fly from the 3d models or mathematical formulas. I would think it uses look-up tables?
   
2. FSX, although coded before today's advanced graphic cards, can be tweaked to a degree because of the programers clever coding. I've also read that many believe that the code was poorly done. I don't buy this myself as much of the graphic processing can be off loaded from the CPU to the GPU (graphics card) with all the inherent dangers that go along with that.
   
3. FSX was coded before today's multi-core processors but with Service Packs 1 and 2 applied can take some advantage of them. A core for FSX itself, core's for texture loading, and core 0 for a thread that I can't for the life of me remember.
   
4. Good game play does not come from fast frame rates, but from perceived smoothness, and sharp textures. I whole heartily agree with this.
   
5. The basic in game settings can and do influence the perceived smoothness and graphical quality of the simulation, just not the way most would think. For example lower auto-gen and scenery density settings don't necessarily translate into a smooth flight experience with sharp textures.
   
6. A clean, lean, and mean install of your operating system is a must, PERIOD
   

 

Hardware wise:

1. The faster the CPU, the better. A no brain-er! This would also mean, I would think, that the faster the bus speeds and memory timings, the better.
   
2. The more physical cores a CPU has (after SP1 and SP2) doesn't necessarily mean more performance as the coding only executes on one core, core 0 (although there's that single thread which always runs on core 0 – wish I could remember the name of it). Texture loading is done on the other cores which would be of limited benefit depending on bus speeds and memory timings, which as a whole would limit the point to which the number of physical cores would be a benefit. Of course this can be “tweaked”, and the cores assigned. Un-tweaked, FSX and the “special thread” execute on core 0, leading to something called thread collisions.
   
3. Virtual cores on a CPU are of no benefit, and hyper-threading can introduce shutter's, etc.
   
4. Graphic cards in SLI or “crossfire” are of no benefit.
   
5. ATI Graphic cards have many thousand more processors (pipelines or whatever) than Nvidea cards and can handle much larger amounts of data thrown at them, but the Nvidea cards fewer processors operate at much higher speeds, both of which are useless given that FSX is CPU bound concerning the graphics, that is until one starts to tweak and unloads the graphical rendering from the CPU to the GPU. At this point each graphic card has it's own and different benefits.
   
6. Over 4 gigabytes of RAM is unless as FSX is a 32 bit program and can only address, or point to, memory up to a certain maximum (3 gigs I believe). This only applies to FSX running by itself, and a 64 bit operating system is of great benefit in eliminating most out of memory errors due to add on scenery, complex aircaft, etc. I haven't had any OOM's since switching to Win7 64 bit.
   

 

Those are my basic understandings of the way FSX works, and it's inherent limitations.

 

I do not have a fast computer or graphics card but do get, for the most part, a smooth flight and sharp textures. I try not to look at my “frames per second” as it's not the point. A smooth flight is.

 

I have applied many “tweaks” and have tested them, some have worked, and many have not. I would like to discuss them and my perceived understanding of how they work and interact of each other at a later date.

 

For example as I expand my flight experience to include add-on scenery I'm starting to observe blurries when the textures are 4096 bits (or is it bytes). I understand, at least I think I do, the way the external frame limiters affect this. No external frame limiter, hardly any blurries. No external frame limiter, the flight is no longer smooth. I've read that the external frame limiter not only caps the frames, but in doing so also caps other things within FSX itself. I've tested this. I always ran the External frame limiter capped at 15fps with nice smooth flights and sharp scenery textures. However with complex scenery with 4096bit textures blurries were introduced, which I believe is because FSX, in default, wasn't allocating enough time to load the scenery textures. I then set “FIBER_FRAME_TIME_FRACTION” to 1.0 (I know; overkill) just to see what would happen... less blurries. I then capped the external frame limiter to 60 and the blurries are mostly gone. I how have stutters, but not in slow aircaft. I believe that FIBER_FRAME_TIME_FRACTION is the amount of time that FSX assigns to texture loading as compared to rendering the scene. I've long ago unloaded the rendering from the CPU to the GPU with “BUFFERPOOLS=0” so should be able to command FSX to ignore rendering and devote texture loading as high as I want with FIBER_FRAME_TIME_FRACTION, which of course is not the case as other factors also come into play and must be balanced.

 

Just some food for thought, and I'm now running on at the mouth. Sorry.

[Chock 17,769]

I thought it was tiny CIA agents inside my ATI card which moved the pixels around. I'll be very disappointed if I learn that this isn't the case, in fact I will feel that I have been misled, since it does say 'intel inside' on a sticker on my PC. The CPU is evidently something to do with a main highway in California, since apparently that is an i7. I do know my laptop is operated by two tiny US Marines from the intelligence staff inside the CPU, because that is an Intel Corp Duo according to the sticker on that one. They may possibly be assisted by a seamstress on amphetamines, as it does something called hyperthreading too, although she is apparently hampered by her reliance on public transport to get to work, because her efforts are supposedly constrained by bus speeds, and it is allegedly a hard drive too from what I have surmised. Sadly, I understand that she also has to spend much of her earnings on plumbing maintenance, since she needs pipeline burst cash.

 

Al

[woodhick 504]

Chock, I'm.... Well, I guess I'm stunned by your clarity of thought and magic ability to explain things so clearly. All else that has gone before is as chaff in the wind. Thank you Great Master. Thank you Great Master. Have you considered a presidential run this year??

 

All kidding aside, I really enjoyed your somewhat tongue-in-cheek commentary.

[Andayle 47]

I thought it was tiny CIA agents inside my ATI card which moved the pixels around. I'll be very disappointed if I learn that this isn't the case, in fact I will feel that I have been misled, since it does say 'intel inside' on a sticker on my PC. The CPU is evidently something to do with a main highway in California, since apparently that is an i7. I do know my laptop is operated by two tiny US Marines from the intelligence staff inside the CPU, because that is an Intel Corp Duo according to the sticker on that one. They may possibly be assisted by a seamstress on amphetamines, as it does something called hyperthreading too, although she is apparently hampered by her reliance on public transport to get to work, because her efforts are supposedly constrained by bus speeds, and it is allegedly a hard drive too from what I have surmised. Sadly, I understand that she also has to spend much of her earnings on plumbing maintenance, since she needs pipeline burst cash.

 

Al

 

HAHAHAHAHAHAHA That's just fantastic.

 

 

 

For the OP

 

That's an interesting theory on how FSX operates and performs, something I'm currently interested in as I will be hopefully upgrading my whole PC just for FSX.

[Doc943 0]

A reasonably good account of things I thought ty

[Bert Pieke 7,593]

I think you are pretty close on the FSX workings, but Bufferpools=0 as best I know,

simply removes a buffering step from the CPU to GPU path. This only works if you have

a fast GPU that can handle all you can throw at it "in flight" so to speak..

 

As for the Cores, FSX will always run a basic set of threads on Core0, no matter what.

 

The main load can be moved off Core0 by using the Affinity Mask setting. (14 for a four Core CPU).

 

Ever since SP2, FSX will use additional CPU cores for texture loading, but with diminishing returns

past two cores.

[spesimen 135]

Gentlemen;

 

Like many of you I have read with intense interest all the threads here, and else where, concerning the tweaks and inner workings of Microsoft's Flight Simulator X. I think I understand most that I have read, and am sure I've misinterpreted others. I just wondering how well I do understand it. So here goes. This is my understanding of how FSX works.. Please correct or comment.

 

well here's a few comments..

 

 

1. yeah, although this is partially due to different expectations and settings, not to mention the wide variance in performance with different mods. the odds of 2 people using identical systems and configs is so rare it's always apples and oranges.

 

1. yes, cpu limited in fact. while you are correct that current video cards are much more advanced now... the writing was already on the wall, fsx was notoriously dog slow on otherwise respectable systems back in the day. it never really had a thorough decoupling of the renderer in a way that could take full advantage of what cards could do at the time either. it's pretty impressive for what it does, though.

 

as a side bar, the physics calcs you are talking about are pretty trivial for a modern cpu it's highly unlikey they'd need somethign like a lookup table with so many ghz of highly optimised fpus in the chip.

 

2. yeah, well all a matter of opinion for sure.

 

3. yeah

 

4. also a matter of opinion. high frame rates and more specifically high average framerates contribute greatly to perceived smoothness. people will argue till they are blue in the face no matter what lol... :)

 

5. see #1. lower auto-gen usually improves smoothness and frames for me when i'm using demanding aircraft

 

6. well, pretty much good advice in general :)

 

 

 

hardware

1. yeah

 

2. pretty much. though it can be leveraged if you run mods that use cpu though like for weather or atc and so forth

 

3. i've never really seen any scientific benchmarks on this, it's an interesting topic. it's my understanding that fsx won't take advantage of it but that it's not necessarily degrading performance either... i hear talk of 'thread collisions' but i've never seen any real evidence that is occuring in a way that would measurably affect performance, we are talking about things that happen in a few microseconds here. i'm not even sure how you'd really gather those stats without a debug copy of fsx anyway.... now one definite way turning it off could help is that a lot of folks say you can acheive higher and cooler overclocks with it turned off....which does have a direct affect on fps! for me i leave it on because i use my computer too much for other stuff that takes advantage of it and rebooting and messing with my bios every time i want to run fsx is a hassle.

 

4. i believe this is the general consensus yeah

 

5. depends entirely on which models you are talking about, but yeah pros and cons each

 

6. yeah, having plenty of ram does help if only to ensure that fsx gobbles it's full 4gb by itself and not sharing with the OS at all. when i run with all my mods and stuff going and a few browser windows for charts i'm often using 7 gigs or so. upgrading from 6 gigs to 18 gave me an impressive reduction in stutters.

 

anyway good food for thought, nice post

cheers,

-andy crosby

[Solren 1]

I thought it was tiny CIA agents inside my ATI card which moved the pixels around.

:P

 

I think you are pretty close on the FSX workings, but Bufferpools=0 as best I know,

simply removes a buffering step from the CPU to GPU path. This only works if you have

a fast GPU that can handle all you can throw at it "in flight" so to speak..

 

As soon as I read that I realized I already knew it, but over the last year had started to misinterpret it.

 

So I went off in an unattainable tangent thinking that the rending of the scenery was removed from the CPU by the Bufferpools=0 switch. Hmm... how easily we read into something that isn't there when we really know the difference.

[virtualstuff 770]

I thought it was tiny CIA agents inside my ATI card which moved the pixels around. I'll be very disappointed if I learn that this isn't the case, in fact I will feel that I have been misled, since it does say 'intel inside' on a sticker on my PC. The CPU is evidently something to do with a main highway in California, since apparently that is an i7. I do know my laptop is operated by two tiny US Marines from the intelligence staff inside the CPU, because that is an Intel Corp Duo according to the sticker on that one. They may possibly be assisted by a seamstress on amphetamines, as it does something called hyperthreading too, although she is apparently hampered by her reliance on public transport to get to work, because her efforts are supposedly constrained by bus speeds, and it is allegedly a hard drive too from what I have surmised. Sadly, I understand that she also has to spend much of her earnings on plumbing maintenance, since she needs pipeline burst cash.

 

Al

 

Lol that sums it up together nicely :-)