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