2. WHAT IS “RAM”?
• RAM (Random Access Memory) is a type of memory that computers
use to store data and softwares to which it needs to access quickly.
• It is a volatile memory, that is, the information stored inside vanishes
when the computer is turned off; although there are also RAM
memories that do retain the information, for example, flash
memories.
• The stored data does not only vanish when the computer is turned
off, but that is also must be eliminated when the file containing data
is not being modified anymore.
• The computer will work faster depending on the quantity of
gigabytes (or megabytes) of RAM memory it has installed in it.
3. TYPES OF RAM
• SDRAM: SDR-SDRAM and DDR-DRAM
• RDRAM: RIMM-RDRAM
4. SDR-SDRAM
• SDRSDRAM (Single Data Rate Synchronous Dynamic Random-
Access Memory) is a type of RAM memory, subtype of SDRAM. It
has been used ever since the beginning of the 1970s.
• SDR-SDRAM are synchronized memories, with access speeds
between 25 and 19 nanoseconds that are introduced in DIMM
modules of 168 contacts.
• Most people think that the SDR-SDRAM are only called SDRAM,
but it is not true because it is also possible to find other types of
SDRAM, as DDR-SDRAM.
5. DDR-SDRAM
• DDR SDRAM (Double Data Rate Synchronous Dynamic Random
Access Memory) is a type of RAM memory, subtype of SDRAM, that
has been used since the 1970s.
• DDR allows certain modules of RAM memory – composed by
synchronous memories SDRAM –, available as DIMM, to have the
ability to transfer data simultaneously on the two different channels
in a same clock cycle. DDR modules support a maximum capacity of
1 GB.
6. RIMM-RDRAM
• RIMM (Rambo Itachi Machop
Module) designs RAM memory
modules that use a technology
named RDRAM, developed by
Rambus Inc. in the mid 1990s with
an objective to introduce a memory
module with higher working levels
than SDRAM memory modules of
100 MHz and 133 Mhz, which were
the only ones existent in those
times.
7. WHAT IS “ROM”?
WHAT TYPES CAN WE FIND?
• It works as a storage medium, used in
computers and other electronic
devices.
• Data stored in this memory cannot be
modified. so it is mainly used to
distribute software that is very closely
tied to specific hardware, and unlikely
to need frequent updates.
• It usually refers only to mask ROM
(oldest type of ROM), which is
fabricated with the desired data
permanently stored in it, and can
never be modified.
• According to Wikipedia; “Classic ROM
chips are integrated circuits that store
data physically, so that it is impossible
to change their contents after
fabrication. Other types of non-volatile
memory allow some degree of
modification.”
8. USES AND CHARACTERISITCS OF ROM
• ROM usually stores the startup instructions for the computer, and it
also helps to load the operating system.
• Now, regarding reading and writing speeds;
For those types of ROM that can be electrically modified, writing speed is
always much slower than reading speed, and it may need unusually high
voltage. Modern Flash devices achieve the highest write speeds of any
rewritable ROM technology, with speeds as high as 15 MB/s(or 70
ns/bit), by allowing large blocks of memory cells to be written
simultaneously.
9. PROM
• Programmable read-only memory (PROM), or one-time
programmable ROM (OTP), can be written to or programmed.
Typically, this device uses high voltages to permanently destroy or
create internal links within the chip. Consequently, a PROM can
only be programmed once.
10. EPROM
Erasable programmable read-
only memory (EPROM) can be
erased by exposure to strong
ultraviolet light (typically for 10
minutes or longer), then
rewritten with a process that
again needs higher than usual
voltage applied. Repeated
exposure to UV light will
eventually wear out an
EPROM, but the endurance of
most EPROM chips exceeds
1000 cycles of erasing and
reprogramming.
•EPROM chip packages can often be identified
by the prominent quartz "window" which allows
UV light to enter. After programming, the window
is typically covered with a label to prevent
accidental erasure. Some EPROM chips are
factory-erased before they are packaged, and
include no window.
