Amplitude, charge and recovery time for a single cell and real SiPMs for under- and oversaturation light intensities have been investigated. It has been shown that a SiPM illuminated by high intensity light flash (many photons/SiPM cell) is able to generate a signal with an amplitude that is higher then A1$\times$N, where A1 – one-cell signal amplitude for low light conditions, N - total number of cells inside the SiPM. This effect can be explained by creation of multiple avalanche starting points inside of a SiPM cell which leads to the development of multiple avalanches inside of the cell and thus to a higher discharge current with shorter pulse duration when compared with a case of a single avalanche per cell. It will be shown that under strong oversaturation conditions even the charge from SiPM cell is not remaining a constant and increases with increasing intensity of light. The later effect leads to longer cell recovery times for higher light intensities. Work has been supported by Megagrant 2013 program of Russia, agreement N14.A12.31.0006 from 24.06.2013

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