Memories

                                                         


Memory:
 Memory means to remember something in its mind. Think of memory as a vast bank of switches with two positions: on or off. Off is given the value of "0"; on is given the value of "1."
Computer’s memories are given below:
Processor
RAM
ROM
Cache
Microprocessor:
As computer technology advances, your computer will react more slowly, taking more time to process events. Luckily, computers can be easily upgraded. Upgrading your CPU (Central Processing Unit) is one of the most beneficial and easiest things you can do to make your computer run lag-free.
Desktop Versions
Take out your old CPU. Open up your case, un-clip the Heat-sink off the retaining board, and pull the the heat sink off. Some heat sinks require a screwdriver or other proprietary tool to remove.
Open the lever on the side of the socket. Do this by pulling it out, and then pulling it up. Gently lift your old CPU off of the socket.
Take the new CPU out of the box. Line up the gold triangle on the CPU with the one on the socket, and gently let the CPU fall in place. Do not force the CPU. If it is lined up correctly, it will drop right into place.
Close the ZIF (zero insertion force) lever to lock the CPU. Take the included heat-sink and clip it on using the instructions. If your heats-sink doesn't have thermal paste or pads on it yet, apply a very thin layer of it. If the heat-sink includes a fan, plug it into its proper connector. Do not operate a CPU without thermal transfer material or a heat-sink in place.
  You have just installed your CPU! Power up and enjoy your upgraded computer.



Cache:
It is intelligent buffer. A cache contains the data accessed between a slower peripheral device (RAM) and the faster CPU. Cache is high-speed memory than RAM. But cache quantity is slow.
There are two types of cache.
L1 Cache
L2 Cache
L1 Cache:
               L1 Cache is made directly on the processor die. Therefore, the L1 cache always ran at the full speed of the chip that is CPU (microprocessor). It is also called internal cache.
L2 Cache:
               L2 Cache on the motherboard is called second level cache ran at the slow speed of the motherboard. It is also called external cache.
BUSES:
“A collection of conducting wires which is responsible for communicating signals from one place to another place in a computer system.”
 “A bus is a “highway” of digital signal it consist of a set of physical connection (printed circuit tracks and wires) over which the data and other information are moved for one place to another place”.
Address Bus:
The address bus requests the memory location from the memory or I/O location from an I/O device. If an I/O is addressed, address bus contains 16-bit I/O address. The 16- bit I/O address selects one of the different I/O locations.
Data Bus:
The data bus transfer the information between microprocessor and its memory an I/O locations. Data transfers vary in size depending upon the microprocessor.
Control Bus:
The control bus contains lines that select the memory or I/O and cause them to perform read or write the operations.
Understanding Expansion Buses
Expansion cards are integrated circuit card that plug into an expansion slots on a motherboard to provide access to additional peripherals or features (such as video, sound, image capture cards, etc.) not built into the board. Also referred to as an add-in-board. Expansion slot is a slot on the motherboard that physically and electrically connects an expansion card to the motherboard and the system busses.
Today  we use following buses which are use to transfer data:
PCI
AGP
PCMCIA
PCI:
The PCI bus specification was released in June 1992 as version 1.0 & since then have several upgrades.
The best features of the PCI slots are as bellow.
PCI cards do not have any jumpers, switches and are configured through the software.
PCI designs use special bus and chip set for advance bus mastering techniques. This allows to supports more than three PCI slots.
The PCI bus has its own set of Interrupts number for each slot, if a PC have more than four PCI slots,           some of them will be sharing interrupts and IRQ,s



AGP:
AGP version 2.0 was released in May 1998 and added 4X signaling as well as a lower 1.5v operation capability.
The latest version of AGP specification for PC,s is AGP 8X, which was announced in August 2000. It defines a faster 8x transfer mode for ever-greater performance than before. AGP command is found only on Pentium II and late computer systems The standard AGP 1x/2x, AGP 4x and AGP pro slots are compared to each other in the pictures.

AGP 4x and AGP pro can accept AGP 1x, 2x and 4x cards.
Heat Sink:
“To cool a system in which processor heat problem you can buy a special attachment for the CPU chip called a heat sink.”
When a computer system works, its processor consume power, therefore processor generate heat and this heat causes many problems for used to absorb heat on to the processor chip. Heat sink is made of a special metal, which carry heat away from the processor, data into fins. Fins that expose heat to moving air.
Types of Heat Sink:
There are two types of heat sink:
Passive Heat Sink:
The passive heat sinks for the socket processor showing a various attachment method and have no fan built into them.

Active Heat Sink:
The active heat sink for the processor have fan built into them.

The Motherboard:
The motherboard is usually the largest circuit board found inside the computer case. With out doubt, the most important component in a PC system is the main board or motherboard. Some companies refer to the motherboard as a system board or planar. The terms motherboard, main board, system board, and planar are interchange able. The function of the motherboard is to provide the connectivity for all devices (Input, Output, Storage), as well as for the CPU, RAM, and support ICs. It also defines the computer’s limits of speed, memory, and expandability.  Figure shows the Structure and connectors of the motherboard.