I used GPFax on a stock A500, then later when upgrade with a GVP A530Turbo, under AmigaOS 1.3 up through 3.1. With it I used an Emerson 2400bps modem, then a 14.4 modem (can't remember the brand, but I think is was a Supra) In all configurations it worked great, with the exception of not being able to share the serial port device with Miami.
