1. Memory Holding area for data, instructions, and information
Consists of electronic components
store instructions waiting to be executed by the processor
data needed by those instructions, and
results of processing the data (information).
Stores both programs and data
CPU cannot hold permanently
Small chips on the motherboard or on a small circuit board attached with motherboard
Allows CPU to store and retrieve data quickly
More memory makes a computer faster 1

2. Memory Address Bit –smallest storage unit
Byte (character)– smallest addressable unit
Room vs House
Each memory cell has an address
An addresses is a unique number that identifies the location of a byte in memory. 2

3. Memory Size Byte is a basic storage unit in memory
Memory and storage devices size is measured in KB, MB, GB or TB 3

4. What Memory Stores? The operating system and other system software
Store Instructions waiting to be executed by the processor
Data needed by those instructions, and
Results of processing the data
Stores three basic categories of items:
The operating system and other system software
Application programs
Data being processed and the resulting information 4

5. Volatile memory Nonvolatile memory Types of Memory
Loses its contents when power is turned off
Example includes RAM
Nonvolatile memory
Does not lose contents when power is removed
Examples include ROM, flash memory, and CMOS 5

6. RAM Random Access Memory (RAM) Requires power to hold data
Data in RAM has an address
CPU reads data using the address
CPU can read any address
Teaching tip
One of the most commonly asked questions is “How do I speed up my computer”. The simplest answer is to add RAM. The Productivity Tip on page 200 provides some guidelines when to add RAM. 6

7. RAM main memory or primary memory
Misnamed as all semiconductor memory is random access
random access means individual words of memory are directly accessed through wired-in addressing logic.
Read/Write
Volatile
A RAM must be provided with a constant power supply. If the power is interrupted, then the data are lost.
Can only be used as temporary storage
Today, the use of semiconductor memory chips for main memory is almost universal.
Properties
exhibit two stable (or semi stable) states, which can be used to represent binary 1 and 0.
capable of being written into (at least once), to set the state. 7

8. Magnetoresistive RAM (MRAM)
RAM Chip sets
Static RAM
Dynamic RAM (DRAM)
Magnetoresistive RAM (MRAM)
Dynamic RAM (DRAM)
Static RAM (SRAM)
Magnetoresistive RAM (MRAM) 8

9. Static RAM Bits stored as on/off switches
Stores data without need of frequent recharging
No refreshing needed when powered
More complex construction
More expensive
Faster and more reliable
No need to wait to access data during processing
Fast memory Cache uses SRAM chips 9

10. Dynamic RAM Bits stored as charge in capacitors
presence or absence of charge in a capacitor is interpreted as a binary 1 or 0
Capacitors have a natural tendency to discharge.
dynamic refers to this tendency of the stored charge to leak away, even with power continuously applied.
Need refreshing or recharging even when powered
Need refreshing or recharging to maintain data otherwise lost
Less expensive
Simpler construction
Processor cannot access data during refreshing or recharging
Slower than SRAM 10

11. SRAM v DRAM Both volatile Dynamic cell Static
Power needed to preserve data (bit value)
Dynamic cell
Simpler to build, smaller
More dense (smaller cells= more cells per unit area)
Less expensive
Needs refresh
Larger memory units
Static
Faster
Cache (both on and off chip)
More expensive
Complex construction 11

12. Magnetoresistive RAM
Stores data using magnetic charges instead of electrical charges
Faster and more energy efficient
MRAM has similar performance to SRAM
Similar density(smaller cells per unit area) of DRAM but much lower power consumption than DRAM,
Much faster and greater storage capacity, ideal for portable devices 12

13. Non Volatile Memory ROM
Read Only Memory (ROM)
refers to memory chips storing permanent data and instructions
Holds data when power is off
Basic Input Output System (BIOS)
ROM BIOS are smaller set of instructions in ROM. These instructions tell the computer how to access the hard disk, find Operating system, loading operating system in RAM
Teaching tip
If you are in a computer lab, spend a few minutes exploring your BIOS. Demonstrate what happens when values are adjusted. Walk through a POST check. Unplug a device and generate POST errors. Be sure to reset everything before moving on with the lecture! 13

14. ROM Types Programmable ROM
PROM
EPROM
EEPROM
Programmable ROM
A PROM (Programmable Read-Only memory) chip is a blank ROM chip that can be written to permanently only once. If there is any error in writing the instructions that error can't be removed from PROM so chip become unusable
Written during manufacture or by user
Programmable (once)
Needs special equipment to program 14

15. Erasable Programmable ROM
An EPROM (Erasable Programmable Read-Only memory) chip is a blank ROM chip that can be written and erased with special devices using ultraviolet rays (UV).
Program and instructions Written during manufacture or by user
Erasable Programmable
User can write new program
Read “mostly” than write operation
Electronically Erasable Programmable ROM
An EEPROM (Electronically Erasable Programmable Read-Only memory) chip is a ROM chip that can be written and erased (data and instructions) using electrical pulses.
Electronically Erasable Programmable
User can write new program and can erase it if error comes
Read “mostly” than write operation
Takes much longer to write than read
Easy to modify 15

16. Semiconductor Memory Types
Category
Erasure
Write Mechanism
Volatility
Random-access memory (RAM)
Read-write memory
Electrically, byte-level
Electrically
Volatile
Read-only memory (ROM)
Read-only memory
Not possible
Masks
Nonvolatile
Programmable ROM (PROM)
Erasable PROM (EPROM)
Read-mostly memory
UV light, chip-level
Electrically Erasable PROM (EEPROM)
Flash memory
Electrically, block-level 16

17. Cache Memory
Small amount of very fast memory which stores copies of the data from the most frequently used main memory locations
Sits between normal main memory (RAM) and CPU
May be located on CPU chip or module
Used to reduce the average time to access memory.
The data that is stored within a cache
might be values that have been computed earlier or
duplicates of original values that are stored elsewhere
If requested data is contained in the cache (cache hit),
this request can be served by simply reading the cache, which is comparatively faster.
Otherwise (cache miss),
the data has to be recomputed or fetched from its original storage location, which is comparatively slower.
Hence, the greater the number of requests that can be served from the cache, the faster the overall system performance becomes.

18. Cache Operation – Overview
CPU requests contents of memory location
Check cache for this data
If present, get from cache (fast)
If not present, read required block from main memory to cache
Then deliver from cache to CPU
Cache includes tags to identify which block of main memory is in each cache slot
Multi Level Cache
Multi-level caches generally operate by checking the smallest level 1 (L1) cache first;
if it hits, the processor proceeds at high speed.
If the smaller cache misses, the next larger cache (L2) is checked, and
so on, before external memory is checked.
L1 holds recently used data
L2 holds upcoming data
L3 holds possible upcoming data

19. Multilevel Cache

20. L1 Cache L2 Cache Built directly in the processor chip.
Usually has a very small capacity, ranging from 8 KB to 128 KB.
The more common sizes for PCs are 32 KB or 64 KB.
L2 Cache
Slightly slower than L1 cache
Has a much larger capacity, ranging from 64 KB to 16 MB
Current processors include Advanced Transfer Cache (ATC), a type of L2 cache built directly on the processor chip
Processors that use ATC perform at much faster rates than those that do not use it
PCs today have from 512 KB to 12 MB of ATC
Servers and workstations have from 12 MB to 16 MB of ATC

21. L3 Cache L3 cache is a cache on the motherboard
Separate from the processor chip.
Exists only on computers that use L2 Advanced Transfer Cache.
Personal computers often have up to 8 MB of L3 cache;
Servers and work stations have from 8 MB to 24 MB of L3 cache.

22. The Bus
A bus allows the various devices both inside and attached to the system unit to communicate with each other
Electronic pathway between components
Two main buses: Internal (or system) bus and External (or expansion) bus.
Internal or System bus:
resides on the motherboard and connects the CPU to other devices that reside on the motherboard
has three parts: the data bus, address bus and control bus
External or Expansion bus:
connects external devices, such as the keyboard,
mouse, modem, printer and so on, to the CPU.
Cables from disk drives and other internal
devices are plugged into the bus.
Bus width is measured in bits
Speed is tied to the clock 22

23. Bus Interconnection Scheme
A system bus consists of a
Data bus,
Address bus
Control bus.

24. Data Bus
is a computer subsystem that allows for the transferring of data
from one component to another on a motherboard or system board
This can include transferring data to and from the memory, or from CPU to other components
Each one is designed to handle so many bits of data at a time.
The amount of data a data bus can handle is called bandwidth
A typical data bus is 32-bits wide(transfer 32 bit data at one time)
Newer computers are making data buses that can handle 64-bit
Address Bus
is a series of lines connecting two or more devices that is used to specify a physical address.
When a processor needs to read or write to a memory location,
it specifies that memory location on the address bus (the value to be read or written is sent on the data bus). 24

25. The width of the address bus determines the amount of memory a system can address.
For example, a system with a 32-bit address bus can address 232 (4,294,967,296) memory locations.
If each memory address holds two bytes(32-bits), the addressable memory space is 4 GB.
Control Bus
A control bus is (part of) a computer bus, used by CPUs for communicating with other devices within the computer.
While the address bus carries the information on which device the CPU is communicating with and
data bus carries the actual data being processed,
Control bus carries commands from the CPU and returns status signals from the devices
e.g. if the data is being read or written to the device the appropriate line (read or write) will be active 25

26. Ports and Connectors
A port is the point at which a peripheral attaches to or communicates with a system unit (sometimes referred to as a jack)
A connector joins a cable to a port 26

27. Ports and Connectors 27

28. Ports and Connectors
On a notebook computer, the ports are on the back, front, and/or sides 28

29. Serial and parallel ports
Serial Port:
Transfer data one bit at a time
Also known as COM (communication) ports
Lower data flow than parallel
Requires control wires
Universal Asynchronous Receiver/Transmitter(UART) converts from serial to parallel
Don’t require fast data transmission like mouse and keyboard
Parallel Port
Transfer data many bits at a time
Extending The Processors Power
Connect to printers or modems
Parallel ports move bits simultaneously
Made of 8 – 32 wires
Internal busses are parallel 29

30. Serial Communications
Universal Asynchronous Receiver/Transmitter (UART) is a type of "asynchronous receiver/transmitter", a piece of computer hardware that translates data between parallel and serial forms. 30

31. Parallel Communications
a parallel interface can handle a higher volume of data than a serial interface
more than one bit can be transmitted through a parallel interface simultaneously 31

32. Bays
A bay is an opening inside the system unit in which you can install additional equipment
A drive bay typically holds disk drives 32

33. Power Supply
The power supply converts the wall outlet AC (Alternating Current) power into DC power
Some external peripherals have an AC adapter(Converter), which is an external power supply 33

34. Machine Cycle 34

35. Machine Cycle Pipelining
Processor begins fetching a second instruction before it completes the machine cycle for the first instruction 35