After struggling with typical OOM (Out Of Memory) errors for a long time....I finally read about major problems.
Every FSX'er banging their head on the desk has experienced this.
It was an epiphany.
A eureka moment. That forgotten sock in the carburetor.
Here are some basic facts every newby should know:
1). FSX from 2006 is a 32-bit program and it can only utilize 4GB max memory internally.
(Prepar3d is 62-bit version which can use your computer hardware fully the way it's supposed to be.)
It doesn't matter if your computer has 500GB RAM. The software can only digest a small part of it.
Software memory is different from computer hardware memory.
2). FSX loads
all enabled scenery at the main menu and not just the location selected!
You must disable all other add-on scenery not being used for that specific flight!
a). After slimming down to only a few countries, the frame rate is now much faster for some reason.
b). The menu and flight now loads within a minute or so.
(Not 15-45 minutes as before.)
I've got about 6Tb of photo-scenery covering much of the world and had it all enabled previously.
I'm now using
https://www.disktrix.com/ultimatedefrag6.html which allows selected programs and files to be placed at the outside of the disk for faster read/write times. Seems to be working good.
c). FSX can now run 100% road traffic without studder. An FSX milestone. Traffic and shadows are well known framerate killers.
I'm now using ProcessLasso from
https://bitsum.com/ which allows programs to be prioritized for CPU usage. Background progs can be turned off or punted to the back of the line. Seems to be working good.
3). I just found out FSX does not un-load scenery from program memory!
(It keeps building up like a giant garbage pile.)
On the internet there are a lot of stories of crash-to-desktop when landing after long flights.
The new airport overloads the program memory, which was already full.
There is not a known solution for this
AFAIK.