slow running arduino due.

bought arduino due, running 10 times slower. delay(1000); 10 seconds waiting. Would you please help?

Really strange !!

When you upload this snippet, what is the result you get in Serial monitor:

void setup() {

Serial.begin(250000);
Serial.print("Systemcoreclock = "); Serial.print(SystemCoreClock/1000000);Serial.println(" MHz");

// output:
//Systemcoreclock = 84 MHz

}

void loop() {
 
}