Found reason for CTDs at ~2450 MB - It is Steam
Steam does provide two versions, the one is the official, the other is named "Beta - w/o support", made by community becausea bug in the original.
But but both don't work correctly, and this is because Steam made own dll.
The original Steam Civ4BeyondSword.exe has 12,528 size and gives CTD when Ram usage is at ~2,340 MB
The "beta" Civ4BeyondSword.exe has in additon a testapp2.exe of 11,374 size and a testapp8800.exe of 12,484 size and gives CTD at ~ 2,450 MB
Now I deleted the orginal Steam Civ4BeyondSword.exe and took the Civ4BeyondSword.exe of 2007 CD (works, Steam identifies if legal by own dll), and with the Steam Original files it gives CTD at 2,540 MB, and with files of "Beta" it gives CTD at 2580 - 2600 MB
So the package of the "Beta" but with the Civ4BeyondSword.exe of 2007 CD gives best result, and also with this the rising of used MB goes much slower than with the both other. I could run more than 200 turns before reach 2,580 while with same save and one of the original Steam exe I could do 40-60 only.
Also I got start the Civ IV now w/o Stream. The problem for Civ IV in Win10 is the d3d9.dll, which is DirectX 11 until Win7, while Win10 is DirectX 12 and Windows "gives" to the graphic card DirectX12, even if the application is set to Win7 in compatibility mode.
I found in my old file storage a d3d9.dll version working with Win10/64, that is file date Nov 20, 2010 file size 2,019 Version 6.1.7601.17514
Portable Executable 64 - 1.97 MB (2067456 bytes) - Saturday 20 November 2010, 15.26.01 - 6.1.7601.17514 (win7sp1_rtm.101119-1850)
(not yet played with it, only test if it starts)
but it was displayed as 5/5
