Because of the low-power design of many Macintosh IIsi components, the computer should be able to handle cards requiring up to 20 watts. Although this exceeds the normal, single-slot, NuBus specification, there is adequate power available in Apple supplied configurations. However, if you use third-party internal hard drives or other components that draw additional power, the power available to the NuBus card may be lower.
All Macintosh IIsi configurations we ship can handle the 15-Watt requirement of a TokenTalk NB Card. It has been tested, and is fully supported with the Macintosh IIsi.