We demonstrate a compact, diode-pumped Nd:GdVO4 laser with a repetition rate of 9.66 GHz and 0.5-W average output power. The laser is passively mode locked with a semiconductor saturable absorber mirror (SESAM), yielding 12-ps-long sech2-shaped pulses. For synchronization of the pulse train to an external reference clock, the SESAM is mounted on a piezoelectric transducer. With an electronic feedback loop of only a few kilohertz loop bandwidth we achieved a rms timing jitter of 146 fs (integrated from 10 Hz to 10 MHz). This is an upper limit because it is mostly limited by the measurement system. The laser setup with a simple linear cavity has a footprint of only 130 mm x 30 mm.