mtu size set 9600

In Cisco ethernet mtu 9600, connect to mikrotik x86 pc 1000 mbps but through put getting 100mbps what should i set mtu

The MTU depend on x86 Hardware used, and if it is fully MikroTik compatible.

The max MTU for MikroTik are 10226 on CCR series.
http://wiki.mikrotik.com/wiki/Manual:Maximum_Transmission_Unit_on_RouterBoards