A SPP stands for "standard parallel port", EPP stands for "enhanced parallel port", while EPP is short for "enhanced capability port".
In theory, any parallel port device should work when plugged into a parallel port set to any of these three modes. But compatibility problems do arise. SPP is the slowest of the three, but it is the one most likely to be compatible. However, in the event of problems, you may have to try each mode until you find one that works.
Where compatibility is not an issue, avoid the standard port and opt for ECP or EPP. ECP is good for transferring large blocks of data and is the mode of choice for scanners and printers -- especially lasers, which receive a whole page of data through the parallel port before printing begins. EPP is most suitable when the direction of data travel switches often, as is the case with ZIP drives and parallel port hard drives.
- Roy Chambers