There are 54 BPM detectors around the ring and most of them are placed inside steering magnets because of quite limited space. The BPM detector is an electro-static type and it has four electrodes, and a pair of electrodes gives a good linear response with a diagonal cut shape to detect the charge center precisely. The signal processing units, which are equipped with 14-bit 40 MS/s ADC and 600 MHz DSP, have been developed. They are accessed via shared memory space and controlled by EPICS. Such a processing unit is capable of recording the full 25 Hz pulse data for the so-called 鈥淐OD mode鈥?(averaged beam position calculation) and it can also store the whole waveform data for further analysis, like turn-by-turn position calculation. The resolution was estimated to be for 鈥淐OD mode鈥?and to be 0.3 mm for the turn-by-turn mode with relatively low intensity of . The position accuracy is estimated to be about 0.5 mm using a newly developed Beam Based Alignment (BBA) method.