How Slots Machines Set Their Payout Percentages
The theoretical payout percentages of slots machines are set at the factory at the same time that the software is written. While changing this payout percentage is possible even after a slots machine has been installed in a casino, it is quite a difficult process that requires physically swapping out the software or firmware, which is generally stored on an EPROM. This software or firmware may also be stored in non-volatile random access memory or NVRAM–and increasingly in CD-ROMs or DVDs, depending on the capabilities of the particular slots machine and the local gambling regulations in place in that jurisdiction. In any case, it is still a time-consuming process even given the current technology, and as such this change is rarely done. In addition, certain jurisdictions such as New Jersey requires the use of EPROMs with tamper-evident seals that can only be changed with the presence of officials of the local Gaming Control Board. In still other jurisdictions, such as in Nevada for example, the slots machines are randomly audited to ensure that only the officially approved software is used.
