Information Technology Reference
In-Depth Information
6.11.11
Which IRQ does an IDE connected disk drive normally use and what is the size of
its data bus.
6.11.12
A floppy disk ribbon cable has a cable twist to differentiate between the A: drive
and the B: drive. How does the ribbon cable that connects two IDE connected
drives differ. In addition, how many wires does the ribbon cable have.
6.11.13
Outline how three hard disks and a CD-ROM can be connected to the IDE bus.
What settings are required for the disks to connect properly? Which signal line
differentiates between a master and a slave?
6.11.14
How are I/O addresses used to communicate with hard disks. How is data trans-
ferred to and from the disk? What are the standard address ranges for the primary
and the secondary? If possible, check these on an available PC.
6.11.15
Which register is used to identify a hard disk error. Explain its operation.
6.11.16
Which is the IDE signal line that identifies if a slave device exists?
6.11.17
Prove that, 16-bit, 44.1 kHz sampled, stereo audio gives over 65 minutes for a
650 MB optical disk.
6.12 Notes from the author
The IDE bus. What can you say about it? Not much really. It has no future plans for glory
and is looking forward to a graceful retirement. It works, it's reliable, it's standard, it's
cheap, blah, blah, and relatively easy to set up. I've spent many a happy hour (not!) setting
the jumpers on CD-ROM drives and secondary hard-disk drives which I want to add to a PC
system. Luckily, these days, modern disk drives and BIOS cope well with adding and deleting
disk drives to systems.
On its negative side, IDE is not really that fast, but it really doesn't have to be, as disk
drives do not require high data rates. E-IDE improved IDE a great deal and only required a
simple change in the BIOS. In conclusion, SCSI is the natural choice for disk drives and al-
lows for much greater flexibility in configuration and also high data rates. But, it tends to be
more expensive, and we'd miss IDE, wouldn't we?
In Chapter 3, I voted the IDE bus as the third most helpful bus of all-time. It merited this
position as, over the years, it has quietly interfaced to disk drives, and has even supported
the addition of CD-ROM drives. By the flick of a BIOS chip, it supported large capacity disk
drives (EIDE). It also requires very little to set it up, as the BIOS tends is able to determine
the capacity of the disk drive, and properly set it up. At present, there are no real plans to
phase the IDE out, thus it is likely to stay a standard part of the motherboard.
Unix workstations and Apple computers have always used the SCSI bus, as it gives easy
external disk upgrades, but, as few users of PC require to add external disk drives to their
computer, there has never really been a great demand for SCSI-based disk drives for the PC.
IDE drives have two interrupts lines set aside for themselves, so why not use them to inter-
face to disk drives. The SCSI bus, though, now offers high data rates, improved connectivity,
improved command and message structure, and easy-of-upgrade. So why isn't it the stan-
dard bus for PC system. Well it costs more, doesn't it, and well, it isn't PC, is it? It's an Ap-
ple thing, isn't it. When has the PC ever done anything in the right way?
Search WWH ::




Custom Search