Space-time diagrams of MREF (panel a), M3 (panel b) and M2 (panel c) with the colours corresponding to the surface density at the respective locations and times. While a TI cycle develops within a 3000 yr time frame in the MREF and M3, the M2 model does not show signs of TI even after about 5000 yr and the disc has reached a quasi-steady state. The white contours indicate the positions of pressure maxima. Panel a1 shows the space-time diagram of the TI phase of the MREF model. The cyan contour line corresponds to the location of the inner edge of the dead zone at the midplane.