Well, it will be best to modify your mod "10000" unit to "1000 capital ship"... collision detection is something enough heavy in sins... a game with 8 player, having each 10000 unit who meet in a gravity wheel for a huge fight mean a very huge amount of collission detection to calculate... now, imagine that these 8x10000 unit are carrier... and that each carrier have two fighter squad... you need to add 8x2x10000 unit for the collission detection... total of 240000 unit !!!...
Same if all the unit are not visible on screen, not in the same gravity wheel but elsewhere in the galaxy, the game need to track them, calculate their trajectory, their stat, etc... huge work for the CPU...
The FPS drop when CPU is over used... the reason is directx... with directx, the way is "texture cached in ram" to CPU, CPU to GPU... when i play on linux, the game use opengl... with opengl, the way is "texture cached in graphic memory" to GPU, if GPU cannot make some work ( miss some hardware accelerated function ) the game fallback to CPU for process and send the processed data to the GPU... so, directx is perfect for low end card with not a lot of memory... in so case, the opengl fallback to CPU will add a huge latency... but if you have a top graphic card, with 1gb dedicated ram or more, opengl will be faster...
A other reason why i play on linux... in the BIOS of my motherboard, i have a option called "discrete MTRR allocation"... when enabled, it greatly improve the graphic performance of the computer when you have more that 4gb ram... problem is that it work on OS like Linux, Unix, Solaris, MAC, etc... but not on Windows... i have plenty of BIOS option on my computer who allow to improve my system but 95% of them are "not supported by Microsoft Windows OS"...
GPU was never a problem... you can have million poly on screen render in real time without problem... by example, 6.25 million poly with a nv9600gs256mb graphic card : http://www.love-from-russia.be/g4_swarm-6.25_million_poly.avi ... have push over 20 million poly on a nv8800ultra768mb ... so, "reduce the sight distance" will solve nothing...
Main memory can be a problem... game crash when it reach 2gb... on windows OS... on Linux, without modify the sins .exe, i can reach 3.9 to 4 gb before it crash... with modify the sins .exe ( setting the flag large address aware ), it crash around 11.5gb ram used... if you remain on Windows, sure that the TSOP mod help a lot... but not in the case of diplomacy since a huge chunk of the TSOP optimization was included in Diplomacy patch...
About CPU, i have two xeon quad core at 2.66ghz... when playing on windows OS ( xp pro x64 ), one of my core is used at 100%... when playing on linux, the game used 6% of the total power ( application jump from one core to the other for balance the "heating" )... when related to a single core, the game use only 48% of the core, and i am playing with the biggest mod who exist, 10 different race and pirates, all setting on very high, everything enable, random huge multistar map ( modified version with 10 star, 2 pirates base by star and 520 planet )...
Point is that "sins of a solar empire" was made for windows OS but it run better on other OS... officially, Stardock don't support other OS but it change nothing to the fact... a lot of the limit and lag are not due to the wonderfull iron engine but to the underlaying microsoft OS... well, need to say that the standart "wine" on linux don't improve a lot the game but a self compiled version optimized for your own hardware do it... if microsoft windows was distributed in a source form and compiled by the user for his own hardware, the OS will run better and will be smaller using less... improving the game performance at a similar level that with Linux...
