하드디스크 스펙을 보는데요

4.2.3 Generalized performance characteristics
Data buffer transfer rate to/from disc media (one 512-byte sector):

SCSI interface data transfer rate (asynchronous):
Maximum instantaneous one byte wide 5.0 Mbytes/sec [4]
Maximum instantaneous two bytes wide 10.0 Mbytes/sec [4]

Synchronous transfer rate Ultra320 SCSI
In low voltage differential (LVD) interface mode 5.0 to 320 Mbytes/sec

Minimum sector interleave 1 to 1
Minimum [3]* 43 MBytes/sec
Maximum [3] 78 MBytes/sec

여기서 one byte wide랑 two byte wide가 무슨 뜻인가요? ㅡㅡ?