Which type of SCSI supports up to 7 devices?

Narrow SCSI is designed to support up to 7 devices on a single SCSI bus. This standard architecture typically employs an 8-bit data bus and allows for a maximum of 7 devices, plus one SCSI controller, making a total of 8 possible connections. Each device is identified by its own SCSI ID ranging from 0 to 6 for the devices and 7 for the controller itself.

In contrast, Wide SCSI utilizes a 16-bit data bus, which enables connection of more devices by effectively expanding the number of SCSI IDs used. Ultra SCSI refers to enhancements in speed and performance over traditional SCSI standards but doesn't specify a unique device limit, as it can still support the same number of devices as Narrow SCSI if it operates on a standard SCSI bus. Serial SCSI, on the other hand, introduces a different methodology that differs from the traditional parallel connection but is commonly used in more modern implementations and does not adhere to the traditional device limitations.