There are 3 related motor driver chips that work with the Handy Board: The SGS-Thomson L293D and L293B, and the Texas Instruments SN754410NE.
The L293D and L293B motor driver chips are closely related. The L293D chip is rated for 600 mA per channel, while the L293B is rated for a whole 1A per channel.
However, the L293D includes spike-protecting diodes on the motor outputs while the L293B does not. This means that the L293B may not simply be substituted for the L293D in motor control applications.
It is possible to wire two of these chips in parallel (e.g., two L293D's or one L293D and one L293B) to gain increased current-carrying capability. This readily done by plopping one IC on top of the other and individually soldering each matching pin together.
Another way to achieve greater power-handling capability on the Handy Board is to use the Texas Instruments TI SN754410 Quadruple Half H driver, which combines the protective diodes of the L293D chip with the greater current capacity of the L293B chip. The SN754410 is a plug-and-play replacement for the L293D.