8 MHz core. Most instructions execute in one or two cycles. Adequate for metering loops reading ADC, updating LCD, toggling PWM. Not for high-speed DSP or control loops above a few kilohertz.
The official TI product status for the MSP430F4260IRGZT is listed as Active, but the evidence also carries an EOL-hot flag. This mismatch is common for parts approaching end-of-life where the manufacturer has not yet issued a formal PCN. If production continuity is critical, ask about the lead time and whether a last-time-buy lot is advisable before the next PCN cycle.
The Flash memory retains data across the full range; the internal oscillator stays within a few percent of 8 MHz over temperature, though an external crystal can be added if tighter timing accuracy is needed.