Evolution of Cyg X-1 over the RXTE lifetime. Vertical lines represent the starting times of the RXTE calibration epochs used in this work: dashed line for epoch 3, dot-dashed line for epoch 4, and dot-dot-dashed line for epoch 5. The total ASM count rate is color-coded according to ASM-based state definition of Grinberg et al. (2013), which uses both ASM count rate and ASM hardness of a given measurement: blue represents the hard state, green the intermediate state, and red the soft state. ASM data points after MJD 55 200 are affected by instrumental decline (Vrtilek & Boroson 2013; Grinberg et al. 2013) and shown in gray. The soft photon index Γ₁ is shown only for those 1980 RXTE observations that were conducted in the B_2ms_8B_0_35_Q binned data mode, see Sect. 2.3. The rms is calculated in the 0.125–256 Hz range (Sect. 3.1), the time lags are averaged values in the 3.2–10 Hz range (Sect. 4.3).