Hi Hong,

the only way to return your 89C664 to life was to have access to a high cost professional universal programmer.

Unfortunately all Philips Flash devices have this dangerous feature.

So, if you can, maybe switch to the Atmels.
E.g. the T89C51CC01 can never be bring in such a state, since force PSEN to low cause always to enter the default boot loader.
Also the default boot loader can never be erased accidentally, since it can only be altered with a professional universal programmer, which apply 12V programing voltage.

So on 5V and with the serial interface you can do all crazy things, whithout any harm.

Peter