That switch is the voltage switch, which is used to set the voltage level appropriate for the country where you are using the Macintosh Performa 6400 computer. This voltage switch MUST be set correctly to avoid damaging the computer.
The voltage switch can be set to 115 or 230 voltages. Use 115 for voltages between 100 and 130. Set the switch to show 230 for voltages between 200 and 270. Insert a screw driver in the slot to set the switch to the appropriate setting.
Below is a listing of the voltage requirements for some countries. Some countries use two standardized voltages (for example, either 100 or 220).If you are not sure which voltage you have, check with the electricity supply company before plugging in the Performa 6400.
| Country | Single Voltage |
| Japan | 100 |
| Algeria, Indonesia, Lebanon, Libya, Peru, S. Korea, Vietnam | 100 or 220 |
| Ecuador, Jamaica, Philippines, Taiwan | 110 |
| Bermuda, Canada, Puerto Rico, United States, Venezuela | 120 |
| Colombia, Mexico, Saudi Arabia | 127 |
| Brazil | 127 or 220 |
| Hong Kong | 200 |
| India, South Africa | 220-250 |
| Israel, Pakistan, Singapore | 230 |
| Australia, Kuwait, Malta, New Zealand, Northern Ireland, Papua New Guinea, Oman, Qatar, United Kingdom | 240 |
| Austria, Belgium, Denmark, Finland, France, Germany, Greece, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland | 220-230 |
| Bahrain, Chile, China (People's Republic), Czechoslovakia, Egypt, Greenland, Hungary, Iceland, Iran, Jordan, Liechtenstein, Nepal, Paraguay, Poland, Romania, United Arab Emirates, Russia and the Commonwealth of Independent States, Yemen, Yugoslavia | 220 |