SCSI ans IDE
Serial Attached SCSI is running SCSI command set on the electric and physical lyers of Serial ATA. So call it “SAS”.
SCSI ans IDE:
1.Connecting ability: Ultra SCSI has 16bit host bus, and each SCSI channel holds 15 devices; IDE is also 16bit as SCSI,but only two devices would be supported. The length of ATA cable should not be more than 0.5m.
2.Adapter: In the early, ATA used PIO(Programmer Input Output) transfer mode, every I/O operation need CPU resource, so the processor is alway in a high working rate, even sometimes the whole system looks halt without no responding.With the development to Ultra ATA, DMA(Direct Memory Access) increases the performance, the system accesses interface device through DMA, not as former tools “CPU”. To SCSI, it has its own powerful adapter which need litter cpu resources.
3.ATA Channel: ATA Channel is not shared.The primary channel has he prior, for example, it is why we usually set the harddisk to “primary” or “slave” when having two. Note, whoever hold the ATA channel, the other one device could not access and only has to wait for the ending of the current one.