Trouble

Nucleo-F303K8 board can change a system clock setting using a hardware configuration as follows.

Trouble is that SB4=Short, SB6=open configuration cannot start HSE mode and stay in HSI mode.
............................Original...................................................................... Modified...........................

Solution

I'm not sure but need to modify following file.
\targets\TARGET_STM\TARGET_STM32F3\device\stm32f3xx_hal_rcc.c
During transient between HSIand PLL to HSE PLL, system needs to disable PLL.
Current control program cannot take over the system clock from HSI+PLL to HSE+PLL then return without successful condition.

Tentative solution

Start form HSI+PLL then set HSI without PLL (8MHz clock), after those step change to HSE+PLL

Permanent solution

I would like to ask ST team to improve this issue.
ST team point of view, this is not a bug but specification.
Because you can see following program.
When PLL is running, following program give up PLL setting.

HAL_StatusTypeDef HAL_RCC_OscConfig(RCC_OscInitTypeDef  *RCC_OscInitStruct)
{  
   ; // Omitted

  /*-------------------------------- PLL Configuration -----------------------*/
  /* Check the parameters */
  assert_param(IS_RCC_PLL(RCC_OscInitStruct->PLL.PLLState));
  if ((RCC_OscInitStruct->PLL.PLLState) != RCC_PLL_NONE)
  {
    /* Check if the PLL is used as system clock or not */
    if(__HAL_RCC_GET_SYSCLK_SOURCE() != RCC_SYSCLKSOURCE_STATUS_PLLCLK)
    { 
	   ; // Omitted

    }
    else
    {
      return HAL_ERROR;
    }
    return HAL_OK;
}

I hope they can put good code into line 18 to resetting PLL even PLL is running.
Thanks in advance.