A method of transferring data that does not require that the bus wait for a REQ-ACK handshake for each byte of data. Instead, the target is allowed to send a number of REQ pulses without waiting for return ACK pulses. This number of REQ pulses is called the "offset". Offset is the maximum number of unanswered REQ pulses that can exist at a given time and may be any number although it is normally something like 8. Offset eliminates the requirement to wait for an ACK for every REQ and avoids the effect of propagation delay in the SCSI cable. The result is a more efficient utilization of the SCSI bus bandwidth and gives a maximum data transfer rate of 5 Megatransfers/second for SCSI-1 NARROW, 10 Megatransfers/second for FAST SCSI and 20 Megatransfers/second for Ultra SCSI. All SCSI bus negotiations, even on a synchronous SCSI bus, are carried on asynchronously. On a synchronous SCSI bus, only the actual data transfers are accomplished synchronously.

This definition is in context to SCSI. See more contextual defintions for Synchronous (SYNC) Transfer.