Multichip modules (MCM) have been successfully built and operated. These use 4 single-photon counting MPEC 2.3 chips that are bump bonded to 1.3 cm × 1.3 cm CdTe or Si semiconductor pixel sensors. Single-chip detectors were built as well. The MPEC 2.3 chip provides a pixel count rate up to 1 MHz with a large dynamic range of 18 bits, 2 counters and energy windowing with continuously adjustable thresholds. Each MPEC has 32 × 32 pixels of 200 μm × 200 μm pixel size. For a MCM the 4 chips are arranged in a 2 × 2 array which leads to a 64 × 64 sensor pixel geometry. The MCM construction is described, and the imaging performance of the different detectors is shown. A newly developed USB readout system has been used.