I finally found on the net the following excellent Basic routine written by R. Broucke at the University of Texas, Austin, which has been tested on several 80's 8-bit PCs to compare their speed and accuracy, measuring the propagation error due to the lack of mantissa precision.
Great Cow BASIC is a set of open source BASIC programming tools for Microchip PIC and Atmel AVR microcontrollers:
Great Cow BASIC has been written with three main aims – to remove the need for repetitive assembly commands, to produce efficient code, and to make it easy to take code written for one chip and run it on another. It hides many of the more confusing parts of microcontroller programming, making it suitable for beginners and those who don’t like assembly.