STM32F746NG Discovery RAM STemWin problem (add external SDRAM)

// Define the available number of bytes available for the GUI

//

#define GUI_NUMBYTES  (1024) *  150

U32 aMemory[GUI_NUMBYTES / 4];

/*********************************************************************

*

*       Public code

*

**********************************************************************

*/

/*********************************************************************

*

*       GUI_X_Config

*

* Purpose:

*   Called during the initialization process in order to set up the

*   available memory for the GUI.

*/

void GUI_X_Config(void) 

{

  //

  // Assign memory to STemWin

  //

  GUI_ALLOC_AssignMemory(aMemory, GUI_NUMBYTES);

}

// Define the available number of bytes available for the GUI
//
#define GUI_NUMBYTES  (1024) *  2048
#define GUI_BLOCKSIZE 0x80
//U32 aMemory[GUI_NUMBYTES / 4] __attribute__ ((section(".GUI_RAM")));

/*********************************************************************
*
*       Public code
*
**********************************************************************
*/
/*********************************************************************
*
*       GUI_X_Config
*
* Purpose:
*   Called during the initialization process in order to set up the
*   available memory for the GUI.
*/
void GUI_X_Config(void)
{
  //
  // Assign memory to STemWin
  //
static U32 *aMemory;
aMemory=(U32*)0xc0000000;//as GUI's RAM buffer
GUI_ALLOC_AssignMemory(aMemory, GUI_NUMBYTES);
GUI_ALLOC_SetAvBlockSize(GUI_BLOCKSIZE);

}

or add comment to main module
//  CPU_CACHE_Enable();