 The 170 shipped with an additional 2 MB RAM card already installed, so it was less of a problem; however, 4 MB was the minimum recommended RAM size for use with System 7 and not practical for use with a RAM Disk, a battery power-saving feature.Though released at the same time as the PowerBook 140 and PowerBook 100, both the 140 and 170 were designed entirely by Apple, while the 100 was being miniaturized by Sony from the full-sized Macintosh Portable.As a result, the 170 represents the very first PowerBook created by Apple, with the 100 actually representing the first design improvements, though its internal architecture is the oldest in the series.