DayZ standalone runs on Real Virtuality 3, the same engine ArmA games do. It is very CPU intensive game engine so no wonder people are having FPS issues with DayZ as it is currently in early access alpha and not optimized yet. Luckily there are things you can do to improve your FPS quite significantly, in my case it was from ~20fps to ~35 in cities and 50-60 out in the wilderness.
Here is a list of things you can try:
1. Install DayZ on SSD (Solid State Drive) most people don’t have SSD but HDD. You can check this by googling your hard drive details. To find out what hard drive you have, go to Control Panel -> Device Manager.
2. Go to “My Documents\Dayz” and open Dayz.cfg there with notepad for example, search for these two lines:
By default there are different numbers so set them to 1 as shown.
3. Go to “My Documents\DayZ Other Profiles \your profile\name.dayzprofile”. Open with notepad again and look for these lines located almost at the end of the file:
These are the settings I have, you can try to increase them if your FPS allows you to, or you can reduce the numbers if necessary.
4. For Steam users. Right click DayZ in Steam library choose properties -> set launch options under general tab. In launch options write -cpuCount=6 -maxMem=6144 -maxvram=3047. Again, these are my settings. Your computer may be different so set the numbers accordingly. I have six-core so my cpuCount is 6 if you have 4 core you just change the number to 4. Same goes for maximum memory and maximum video memory. I have 8gigs of memory and I want to leave 2gigs for everything else running in the background so I put maxMem to 6144. I have 3 gigs of video memory so I put 3047.
Hope this helps!