The ALTGX MegaWizard Plug-In Manager generates a clearbox.exe error when configuring PLLs for Stratix IV GX - The ALTGX MegaWizard Plug-In Manager generates a clearbox.exe error when configuring PLLs for Stratix IV GX Description In the ALTGX MegaWizard Plug-In Manager, on the Modes page of the Reconfiguration Settings tab, if you turn on Enable Channel and Transmitter PLL reconfiguration and Use additional CMU/ATX Transmitter PLLs from outside the Transceiver block , set How many additional PLLs are used to 2 or 3 , and then on the Main PLL page turn on Use central clock divider to drive the transmitter channels using X4/XN lines, clearbox.exe generates an error: clearbox.exe has encountered a problem and needs to close. We are sorry for the inconvenience . Resolution Before you turn on Use central clock divider to drive the transmitter channels using X4/XN lines , on the PLL 2 page , change What is the PLL logical reference index (used in reconfiguration) from 2 to 3 . Custom Fields values: ['novalue'] Troubleshooting novalue True ['PLL'] ['FPGA Dev Tools Quartus II Software'] novalue 10.1 ['Stratix® IV FPGAs'] ['novalue'] ['novalue'] ['novalue']