diskOscope hardware

What is the distribution of raw nibble values of the bitstream a Disk ][ controller would read from an ordinary DOS diskette?

What values would arise from a copy-protected game disk?  Or from a .DSK emulation of a diskette?

This little routine captures incoming nibbles and computes a moving-window histogram of their distribution.  The data usually stablizes after about 8 calls because it applies a base-2 logarithmic decay to the values after each iteration.