We have constructed a modular detector for x-ray crystallography and made preliminary performance measurements. A single detector module consists of a large-area (100 X 100 mm square) fiberoptic taper with a phosphor x-ray converter deposited on the large end and a back-illuminated MPP-mode CCD bonded to the small end. Two or more of these modules can be used together to increase the detector area. The CCD can be operated at -55 degree(s)C when cooled with a two-stage thermo-electric cooler in a 1 atmosphere Xenon-filled chamber. The CCD readout noise is 9e- when read out at a rate of 100 kpixels/second.