All that the presence of frost means is that the suction line or compressor is below freezing, and the moisture in the air has reached its dewpoint temperature and condensed. This condensed moisture has then frozen to ice because the temperature is below 32°F.
Figures 1 and 2 show frost coming back to a suction gas-cooled compressor and an air-cooled compressor, respectively. Figure 3 shows a frosted suction line filter and accumulator. In all three figures, the evaporators had over 9° of superheat and each compressor had over 25° of superheat.