A diagnostic for the magnetohydrodynamic (MHD) mode identification is being implemented on the Tokamak ISTTOK using the signals from the set of 12 equally spaced Mirnov coils. These poloidal magnetic field sensors have been recently installed inside the vessel and were designed for plasma shape and position equilibrium determination. The data acquisition and processing system is based on a locally developed galvanic isolated, eight channel fast PCI transient recorder module with a 2 Msamples/s sampling rate, 14 bit resolution, and a total memory of 256 Mwords. This module includes a digital signal processor and field programmable gate array allowing real-time determination of MHD modes using advanced identification algorithms, in a submillisecond cycle time. Poloidal m number and amplitude measurements are available in real time to feed event-driven active control systems. This solution enables high performance distributed computing, effective data reduction, and event detection at a relatively low cost.