When mixing wide and narrow drives the wide drives go first. A wide to narrow adapter that has high byte termination must be used. In this configuration the slowest drive does not bring the transfer rate for wide drives down to the speed of the slow drives since transfer rate is negotiated between target and initiator. Any perceived performance decrease is due to the fact that faster drives may have to wait for the SCSI bus while a slower drive is delivering data. This is one reason for decreased overall performance with slower drives on the SCSI chain. This same theory applies on an all-wide or all-narrow bus. The slowest drive (wide or narrow) does not dictate the individual transfer rates of the rest of the drives. Slower drives will force the faster drives to wait longer before they can transfer their data, thus having the effect of slowing down overall bus performance.