Troubleshooting RAMPS 14

I am building a Laser cutter with CoreXY configuration using only X and Y axes. I managed to get the directions and homing Y before X OK. Only problem is, my max. speed seems to be about 1mm/sec, and whatever I do does not move axes in the correct speed. The scale - distance travelled seems OK.
I tried various selection of boards, as RAMPS 14 EFB, EEF, SF, no difference. Also in SF mode still demands thermistor, I would have thought the heating should be disabled?
Any suggestions please?

I just tried it with CoreXY commented out, as a normal X - Y system. Still the same 1mm/sec.

check your #define DEFAULT_MAX_FEEDRATE {300, 300, 5, 25} settings

also in eeprom which will override firmware settings (M503 to display them)

Yes, thanks, I have #define DEFAULT_MAX_FEEDRATE {300, 300, 0, 0}
And M503 displays it correctly.

What are your steps/mm ? if they are very large numbers you may just be exceeding the power of the controller (cant send enough pulses fast enough)

My setting as I am configuring it for laser cutting, no Z and E setting :

#define HOMING_FEEDRATE {60, 60, 0, 0} // set the homing speeds (mm/min)

// default settings

#define DEFAULT_AXIS_STEPS_PER_UNIT {80,80,0,0} // default steps per unit for Ultimaker
#define DEFAULT_MAX_FEEDRATE {300, 300, 0, 0} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {3000,3000,0,0} // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for Skeinforge 40+, for older versions raise them a lot.

#define DEFAULT_ACCELERATION 3000 // X, Y, Z and E acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION 3000 // E acceleration in mm/s^2 for retracts
#define DEFAULT_TRAVEL_ACCELERATION 3000 // X, Y, Z acceleration in mm/s^2 for travel (non printing) moves

// The speed change that does not require acceleration (i.e. the software might assume it can be done instantaneously)
#define DEFAULT_XYJERK 20.0 // (mm/sec)
#define DEFAULT_ZJERK 0.4 // (mm/sec)
#define DEFAULT_EJERK 5.0 // (mm/sec)