Couldn't Bring MAX7219 under Control to Display 2?

1016 / 42 = 24.19
316 / 13 = 24.31

Pretty close.

Have you tried using the "LOAD" signal as a "ChipSelect", going low before clocking out the data, and then raising it afterwards?

Thus:

void clkIn(int x)
{
 digitalWrite(8, LOW);
 for (int i = 15; i>=0; i--)
  {
    digitalWrite(11, bitRead(x, i));  //D15 is shifted first
    //------
    digitalWrite(13, HIGH);//generating clock signal
   // delayMicroseconds(1);
    digitalWrite(13, LOW);
  }

  digitalWrite(8, HIGH);
 
}

That's how it works using SPI, if I'm reading the datasheet correctly.