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COMPUTER HARDWARE 93
MEMORY CHIPS
Oh yes! Most computer memories actually contain memory chips. These are integrated
circuits that contain thousands or millions of individual bits that the computer can read
and write. A few different types of memory are available, and they all bring different
benefits to a robot project. It makes sense to know about the most popular types of
memory and what they can do for the robot project.

Flash Memory
Every computer needs a place to store its operating program. The program must not van-
ish when the power goes off. With current technology, almost every computer contains
some flash memory, which contains the initial software that the computer runs when it
boots up. The same flash memory can contain the bulk, or all, of the computer’s software
program. Flash memory’s primary advantage is that it retains its contents in the absence
of power, making it nonvolatile memory. We won’t go into the physics of it here.
Flash can be programmed when the robot is built and will retain the program through-
out the life of the robot. Most flash memory can be reprogrammed in the field if the
program must be changed. Beyond just storing the program of the computer, the flash
memory can be used to permanently store other data the robot may gather, almost like
a disk system.
One caveat, however, is that many types of flash memory can only be written to a
specific number of times before failing. The flash memory chip specifications will
detail how many times the flash can be written to. So if a need exists for nonvolatile
memory storage now and then, consider putting flash memory into the robot.
Sometimes this sort of memory can be added to a robot’s computer using Personal
Computer Memory Card International Association (PCMCIA) cards, which we’ll talk
about in a bit.

Static Memory
This is a type of volatile memory, which is relatively simple to use from an electrical
engineering perspective. It does not require complicated timing. However, static memo-
ries are generally smaller for equal dollars and have fallen out of favor. They generally
use two to four transistors just to store one bit of memory, whereas the cheapest
(Dynamic Random Access Memory [DRAM]) memories use just one transistor to store
a bit. One thing static memories are good at is battery backup. Static memories can be
made nonvolatile with the addition of a battery. They are often teamed up with lithium
or other such batteries that have a long shelf life. Some types of static memories consume