With all of the posts of crashes and the discovery that some of you have only 4 GB RAM, I thought of running a measurement check I have run before and posting the results here. It helps to illustrate how much RAM gets assigned by the OS to back up the virtual memory used by GC3 as it stands at build 0.71.1. Memory use optimization typically doesn't happen until shortly before release, so Stardock may be able to reduce this by some at that time.
Also note that my computer has plenty of spare RAM at 16GB, so I seldom, if ever, see any page thrashing. If you have less than 6GB then you will surely encounter the extreme delay that can occur with heavy page thrashing.
My configuration is:
Windows 8.1 with Stardock's "Start8", a sidebar manager (not available in Win8) with CPU and GPU usage and temperature monitors.
Intel I7-4770 at 3.40 GHz. (I don't use overclocking, in fact, if I read the Intel specs correctly, this chip does it automatically as needed.)
16GB RAM
2 TB hard drive (not a factor for these measurements).
NVidia Geforce GT 640 and 4GB RAM with "NVIDIA Geforce Experience". (I get automatic notification of driver updates, including Betas.)
EDIT: I am playing the game in windowed mode at a resolution of 1600*900.
I checked RAM usage by galaxy size and here are my results. The figures are all total amounts. All figures in the first table are just to the first turn. For each measurement, I exited the game and restarted it.
Idle OS + Steam + all the monitors I have running
2.41 GB
GC3 Start menu 3.69 GB -- added about 1.3 GB
GC3 Tiny galaxy 4.49 GB -- added about 0.8 GB
GC3 Small 4.53 GB -- another .04 over Tiny
GC3 Medium 4.56 GB -- another .03 over Small
GC3 Large 4.71 GB -- another .15 over Medium
GC3 Huge 4.92 GB -- another .21 over Large
GC3 Gigantic 5.28 GB -- another .36 over Huge
GC3 Immense 5.92 GB -- another .64 over Gigantic
Then I exited the game and reloaded a game in an Immense Galaxy I had in progress at turn 54 with what looks to me like about 15% of the galaxy explored, all opposing civs selected, all game variables at maximum ("star frequency = abundant", "planet frequency = abundant", etc), 16 colonies, 30 ships, 8 star bases and one shipyard, no mines, rally points, research just barely into the "age of war", and about a dozen custom ship designs.
GC3 Immense reload 6.06 GB -- another .14 over Immense turn 1. If this value scales like I am guessing it will, by the time I have explored the entire galaxy, colonized all of the colonizable planets, done all of the research, etc., I expect to see this value approach or exceed 7 GB, or another 1GB over that for turn 1. (Of course, this is just my guess.)
All of these figures are for this one time. I have seen variances before when I have ran this sequence repeatedly, so, as they say, your mileage may vary. I have seen it go as high as 7.6 GB when playing an immense galaxy.