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SRAM
Tutorial
Background
How
RAM works
RAM
holds code and data so that a computer's central processing unit (CPU)
can find and use it, kind of like the computer's storage space. The
space is divided into sections, so that information can be organized
and locatable, and a
unique, numerical address is added to each section. A
data bus helps move information in and out of the RAM storage and
an address bus allows the computer to specify in which location within
the RAM storage the information should be stored.
RAM
is usually organized in a grid configuration, where each bit is in
its own cell and each row and column has its own address.
SRAM
Definition
- Static RAM
SRAM is a type
of RAM that holds data, placed within its cells, until the values
are either overwritten or the power goes out. This
is opposed to DRAM, which allows the data to exit cells every few
milliseconds unless it is refreshed.
An SRAM bit is
made up of 4 to 6 transistors and is therefore very fast and power
efficient, with
access times in the 10 to 30-nanosecond range. Yet,
because it takes 4 to 6 transistors to make one memory cell, it's
expensive to produce. In comparison, DRAM only uses one transistor
per memory cell and has access times which are usually above 30.
Because of these
properties, SRAM is used to create a CPU's speed-sensitive cache,
while DRAM is used for the larger system RAM space.
Companies
Virage
Logic is a provider of embedded memory. The company's products include
embedded memory cores, software tools and custom memory design services.
Virage Logic's memory compilers are a set of application-specific memory
compilers used by system IC integrators to create silicon-proven memory
cores. The Custom-Touch ASAP product line offers access to a number
of embedded memory cores that are optimized for each application. Specifically,
the ASAP line offers five families of Custom-Touch Memory Compilers;
High Density, High Speed, Ultra Low Power, Register-File and ROM.
TSMC,
who is also mentioned in the article, is a semiconductor foundry that
provides process technology. The company operates two 300mm wafer fabs,
six eight-inch fabs and two six-inch wafer fabs. The company also has
capacity commitments at two joint ventures fabs (Vanguard and SSMC)
and at its wholly-owned subsidiary, WaferTech.
Terms
RAM - Random Access
Memory
Memory
chips which function as the computer's primary workspace (RAM is where
you store code and data so the CPU can work with it). The "random" means
that the contents of each byte can be directly accessed without regard
to the bytes before or after it. Other types of memory chips, including
ROMs and PROMs have this property as well, but only RAM chips require
power to maintain their content. Therefore, when using RAM users must
save data before turning off their computers.
DRAM - Dynamic RAM
The most common
type of computer memory, which usually uses one transistor and a capacitor
to represent a bit. The capacitors must be energized hundreds of times
per second in order to maintain the charges.
Compiler
Software
that translates a program written in a high-level programming language
into machine language. A utility known as a "link editor" then combines
all required machine language modules into an executable program that
can run in the computer.
Additional
sources of information*
Ars
Technica - RAM Guide
Marshall
Brain's HowStuffWorks - RAM
*The WAVE Report is
not responsible for content on additional sites 9/26/01 |
