ever since 0.15 I experience "micro"-freezes, where the game runs smoothly for a few seconds with UPS=60/FPS=60, then both drop to around ~55-57, which causes the game to freeze for <1sec then it runs smoothly on the lower UPS/FPS for 1-2 sec and then they would return back to 60/60 without a freeze for a few seconds before going through the same process over and over again. This is also not happening for every game session, as in a few occasions this just would not happen in the same save. I tried to turn down the graphics settings, however a real difference is only observed for the lowest setting...
Here it is running on 60/60:

and here the drop

I noticed, that everytime the drop occurs, a spike in disk usage happens (C:\ is system, on K:\ factorio is installed, both SSD's):

both the spikes on C and K seem to correlate with the freezes...
cpu and gpu aren't fully under load as can be seen here:


however a 1-3% spike in the total cpu load can be observed when the freezes occur.
I have attached the save file and the log from the last session
my system:
Windows 7
Intel i5-3560 @ 3.4GHz
Nvidea GeForce 660Ti 2GB Ram
16GB Memory
this problem might be related to viewtopic.php?f=173&t=45236, but to me it seems different and none of the possible fixes I read in the forums worked (e.g. enabling/disabling vsync and so on)