Hardware Reference
In-Depth Information
picnic, and the resulting focus was on using DVD for movie rentals. For example,
standard features include real-time skipping of dirty scenes (to allow parents to
turn a film rated NC17 into one safe for toddlers), six-channel sound, and support
for Pan-and-Scan. The latter feature allows the DVD player to dynamically decide
how to crop the left and right edges off movies (whose width:height ratio is 3:2) to
fit on then-current television sets (whose aspect ratio was 4:3).
Another item the computer industry probably would not have thought of is an
intentional incompatibility between disks intended for the United States and disks
intended for Europe and yet other standards for other continents. Hollywood de-
manded this ''feature'' because new films are often released first in the United
States and then physically shipped to Europe when the videos come out in the
United States. The idea was to make sure European video stores could not buy
videos in the U.S. too early, thereby reducing new movies' European theater sales.
If Hollywood had been running the computer industry, we would have had 3.5-inch
floppy disks in the United States and 9-cm floppy disks in Europe.
Nothing stands still in the computer business, certainly not storage technology.
DVD was barely introduced before its successor threatened to make it obsolete.
The successor to DVD is
Blu-ray
, so called because it uses a blue laser instead of
the red one used by DVDs. A blue laser has a shorter wavelength than a red one,
which allows it to focus more accurately and thus support smaller pits and lands.
Single-sided Blu-ray disks hold about 25 GB of data; double-sided ones hold about
50 GB. The data rate is about 4.5 MB/sec, which is good for an optical disk, but
still insignificant compared to magnetic disks (cf. ATAPI-6 at 100 MB/sec and
wide Ultra5 SCSI at 640 MB/sec). It is expected that Blu-ray will eventually re-
place CD-ROMs and DVDs, but this transition will take some years.
As we mentioned at the start of this chapter, a computer system has three
major components: the CPU, the memories (primary and secondary), and the
I/O
(
Input/Output
) equipment such as printers, scanners, and modems. So far we
have looked at the CPU and the memories. Now it is time to examine the I/O
equipment and how it is connected to the rest of the system.
Physically, most personal computers and workstations have a structure similar
to the one shown in Fig. 2-29. The usual arrangement is a metal box with a large
printed circuit board at the bottom or side, called the
motherboard
(parentboard,
