Another effect of downsizing is a reduction in the data transfer rate. First of
all, most laptop hard drives spin at a slower rate than those in a desktop
machine, which slows down the pickup or putdown of data. Secondly, the
data transfer is fastest at the outer tracks of a drive — tracks with the largest
circumference. Here size does matter — the tracks on a tiny drive are, well,
tinier than a bigger one.Remember, class, that you calculate the circumference of a circle by multiply-
ing its diameter by Π. The diameter of the platters for a 3.5-inch drive, once
you subtract the center spindle and leave a bit of space at the inside and out-
side as a buffer, is roughly 3 inches; say that the diameter of the platter for a
2.5-inch drive is about 2 inches. And, of course, you all can recite the value of
πto 20 places: 3.14159265358979323846. You did know that, right?Obviously, then, a 3-inch circle has a circumference of about 9.4 inches while
a 2-inch circle a mere 6.3 inches. So, even if you leave aside the difference in
rotational speed between a 9,600 rpm 3.5-inch drive and a 4,200 rpm 2.5-inch
device, there’s also the fact that the larger drive has a circumference about
50 percent larger. More circumference means the capacity for more data in a
particular track. At the same rotational speed, more data in a track means
faster throughput.Having a flash of memory..................................................................
Although it is always dangerous to announce that a technology has reached
its zenith or nadir, it does appear that hard drives are not likely to get much
smaller than the current miniature champions of 0.85 inches in diameter. The
problem is that even though engineers continue to increase the density of the
data squeezed onto a disk, the shrinking physical size of the platter keeps
chipping away at capacity.Tiny hard drives are expected to double in capacity to about 8–10GB by 2006,
using new technologies like perpendicular recording, which places sectors on a
more efficient slant instead of at a right angle to the core (outer) circumference.At the same time, makers of flash memory— like the tiny cards used to store
images on a digital camera and in cell phones — are finding ways to make their
nonmechanical RAM chips tinier and tinier and more capacious. And flash
memory offers faster access to data since it is a random access medium — the
controller can go directly to a particular memory location without having to
wait for a spinning platter to come into position under a read/write head that
has to make its own repositioning.116 Part III: Laying Hands on the Major Parts