I am trying to drive a 6V DC motor with an L293D driver and ATmega8 without PWM. The problem is, I am getting a very low speed while connecting the motor via L293D driver.But, It rotates well when I provide direct 6V DC supply to the motor. 

I am using an external 6V source at the VS (motor supply) pin of the L293D but there is no improvement. The motor does not rotate until I turn the rotor by hand. What could be the problem? My code is here:

    DDRB = 0xFF;
    while(1)
    {
      PORTB = 0B00000010;
      _delay_ms(20000);
    }

My simulation design is here:
![Interfacing DC gear motor with Atmega8][1]


  [1]: https://i.sstatic.net/rY3DL.png