Soved: Unexpected SCK frequency with USBasp programmer

with an USBasp connected to the ISP pins of my ATtiny84a board first I loaded the bootloader and then a very simple sketch for testing only.
After both load operations "avrdude: set SCK frequency to 187500 Hz" was reported by the Arduino IDE 1.8.15.

For ATtiny I had selected 8 MHz internal. The sketch (just toggling two pins) works. But what is the meaning of "SCK frequency"?

Hopefully not the CPU clock, and SPI clock is called SCL.
In the final sketch a temperature sensor DS18B20 with onWire interface shall be used, and I hope it will be clocked with a higher frequency.

If somebody needs to see the sketch:

#include <DS18B20.h>
#include <Wire.h>

#error "Sketch was written for clockwise pin mapping!"

#define DS18B20_DATA_PIN  (A2)
#define TEST_PIN        (A3)
#define V_STEPS_MAX   (4)

uint8_t vstate;
float temp, old_temp;
uint16_t lcnt=0;
uint8_t selected;

DS18B20 ds(DS18B20_DATA_PIN);     // Pin mit Data-Anschluss, Tiny:A2, Mega:A6

const uint8_t temp_steps[V_STEPS_MAX] PROGMEM = {25, 28, 32, 36};  // °C
const uint16_t del_steps[V_STEPS_MAX] PROGMEM = {5500, 5000, 3500, 500};

void setup() {
  pinMode(A2, OUTPUT);  // PA2
  pinMode(8, OUTPUT); // PB2
  while(1) {

void loop()  {


It is the clocking frequency used by the USBasp programmer while communicating with the ATtiny84A microcontroller. It only applies to that process. It is not setting a clock speed that will be used by ATtiny84A for other processes.