My blender render view port are so slow in material mode but i don't know the reason

i working on a project for level map for small lowpoly city I have
143 material and i used 111 material from them but the problem is my
view port go so slow the program only use 65% of my ram and less then
50% of the cpu power my all textures are 1500px * 1500px and all my
materials are shadeless I don’t using any lights and I have only 5000
faces on this layer

so what’s the reason ? are the problem from blender our my pc can I do this task in blender our i need another software ?

Hi, Blender is limited here because of it support very old hardware.
This will change with Blender 2.8.
You can try different Window Draw Methode and change Image Draw Methode to GLSL in User Preferences > System.
Uncheck MipMaps can may help too.
You have to restart Blender after change a setting.