3D Wars heeft een artikel in elkaar gezet waarin hij de SCSI interface vergelijkt met IDE. Hieronder vast een hap uit de intro, klik hier voor het hele artikel.
Ultra DMA technology has some very different methods in how it works with the system compared to the SCSI bus. Ultra DMA/66 still has an issue with the amount of data it can get to the processor. Any IDE channel has to share its bandwidth if there are two devices on it. Add to this the way the devices have to use interrupts to access the processor, and the drives must wait in line with other devices you are using at the time, so there is a analogy that imagine a ½ inch garden hose with an average amount of water coming out. Now attach a 2-inch fire hose with the same amount of water coming out. If you shut it off at the end of the hose, and let the pressure build before releasing it, then it can initially seem to be quite an impressive amount of water, but soon it will trickle down.
The difference with SCSI is that it has its own bus to operate on, and data can be transferred among multiple devices simultaneously for added bandwidth and performance. So when I spoke of RAID before, imagine writing to four drives at the same time, and not having to wait for the next interrupt to start again with the process like IDE has to. SCSI has the ability to perform input/output to all of its devices at the same time, so you may be using items like CD ROMs, CD Recordables, external storage devices (ZIP, Jazz drives and RAID enclosures), hard drives and internal ZIP/Jazz drives all at once. So in that regard the initial performance numbers now seem take on a different spin.