Computer System Architecture - Computer System Architecture

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1. Computer Architecture
Week 2

2. Computer Architecture
DEFINITION
Computer architectureis a set of rules and methods that describe
the functionality, organization, and implementation
ofcomputersystems.
The Differences:
Computer architecture = structure and behavior of the various
functional unit of the computer and their interactions
Computer organization = the way the hardware components are
connected to form a computer system

3. Von Neumann Architecture

4. Computer Architecture
Bus
CPU
RAM
Keyboard
Hard
Disk
Display
CD-ROM

5. RAM
•When you talk about the memory of a computer,
most often you’re talking about its RAM.
•If a program is stored in RAM, that means
that a sequence of instructions are stored in
consecutively addressed bytes in the RAM.
•Data values (variables) are stored anywhere in
RAM, not necessarily sequentially
•Both instructions and data are accessed from
RAM using addresses
•RAM is one (crucial) part of the computer’s
overall architecture

6. RAM
2
20
bytes of
RAM
(1 Mega-byte)
Write
Address
Data input Data Output
20 bits of
address
8 bits (1 byte)
of data

8. Computer Architecture
Bus
CPU
RAM
Input/
Output
Devices
Central Processing
Unit

10. The Bus
Bus
•What is a bus?
•It is a simplified way for many devices to
communicate to each other.
•Looks like a “highway” for information.
•Actually, more like a “basket” that they all
share.
CPU Keyboard Display

11. The Bus
Bus
CPU Keyboard Display

12. The Bus
Bus
•Suppose CPU needs to check to see if the user
typed anything.
CPU Keyboard Display

13. The Bus
Bus
•CPU puts “Keyboard, did the user type
anything?” (represented in some way) on the Bus.
CPU Keyboard Display
“Keyboard, did the user type anything?”

14. The Bus
Bus
•Each device (except CPU) is a State Machine
that constantly checks to see what’s on the Bus.
CPU Keyboard Display
“Keyboard, did the user type anything?”

15. The Bus
Bus
•Keyboard notices that its name is on the Bus,
and reads info. Other devices ignore the info.
CPU Keyboard Display
“Keyboard, did the user type anything?”

16. The Bus
Bus
•Keyboard then writes “CPU: Yes, user typed ‘a’.”
to the Bus.
CPU Keyboard Display
“CPU: Yes, user typed ‘a’.”

17. The Bus
Bus
•At some point, CPU reads the Bus, and gets
the Keyboard’s response.
CPU Keyboard Display
“CPU: Yes, user typed ‘a’.”

18. Computer Architecture
Bus
CPU
RAM
Keyboard
Hard
Disk
Display
CD-ROM

19. Inside the CPU
•The CPU is the brain of the computer.
•It is the part that actually executes
the instructions.
•Let’s take a look inside.

20. Inside the CPU (cont.)
Memory Registers
Register 0
Register 1
Register 2
Register 3
Temporary Memory.
Computer “Loads” data
from RAM to registers,
performs operations on
data in registers, and
“stores” results from
registers back to RAM
Remember our initial example: “read value of A from memory; read value
of B from memory; add values of A and B; put result in memory in
variable C.” The reads are done to registers, the addition is done in
registers, and the result is written to memory from a register.

21. Inside the CPU (cont.)
Memory Registers
Register 0
Register 1
Register 2
Register 3
Arithmetic
/ Logic
Unit
For doing basic
Arithmetic / Logic
Operations on Values stored
in the Registers

22. Inside the CPU (cont.)
Memory Registers
Register 0
Register 1
Register 2
Register 3
Instruction Register
Arithmetic
/ Logic
Unit
To hold the current
instruction

23. Inside the CPU (cont.)
Memory Registers
Register 0
Register 1
Register 2
Register 3
Instruction Register
Instr. Pointer (IP)
Arithmetic
/ Logic
Unit
To hold the
address of the
current instruction
in RAM

24. Inside the CPU (cont.)
Memory Registers
Register 0
Register 1
Register 2
Register 3
Instruction Register
Instr. Pointer (IP)
Arithmetic
/ Logic
Unit
Control Unit
(State Machine)

25. The Control Unit
•It all comes down to the Control Unit.
•This is just a State Machine.
•How does it work?

26. The Control Unit
•Control Unit State Machine has very simple
structure:
•1) Fetch: Ask the RAM for the instruction
whose address is stored in IP.
•2) Execute: There are only a small number
of possible instructions.
Depending on which it is, do
what is necessary to execute it.
•3) Repeat:Add 1 to the address stored in
IP, and go back to Step 1 !

27. The Control Unit is a State Machine
Add
Load
Store
Goto
…
…
… …
… …
Add 1
to IP
Fetch
Exec Exec Exec Exec Exec

28. A Simple Program
•Want to add values of variables a and b
(assumed to be in memory), and put the
result in variable c in memory, I.e. c a+b
•Instructions in program
–Load a into register r1
–Load b into register r3
–r2 r1 + r3
–Store r2 in c

29. Running the Program
a
c
2
1
3
Memory
Load a into r1
Load b into r3
r2 r1 + r3
Store r2 into c
2005
2006
2007
2008
2005
Load a into r1
r1
r2
r3
r4
IR
IP
Logic
CPU
2
b

30. Running the Program
a
c
2
1
3
Memory
Load a into r1
Load b into r3
r2 r1 + r3
Store r2 into c
2005
2006
2007
2008
2006
Load b into r3
r1
r2
r3
r4
IR
IP
Logic
CPU
3
b
2

31. Running the Program
a
c
2
1
3
Memory
Load a into r1
Load b into r3
r2 r1 + r3
Store r2 into c
2005
2006
2007
2008
2007
r2 r1 + r3
r1
r2
r3
r4
IR
IP
Logic
CPU
3
b
2
5

32. Running the Program
a
c
2
1
3
Memory
Load a into r1
Load b into r3
r2 r1 + r3
Store r2 into c
2005
2006
2007
2008
2008
Store r2 into c
r1
r2
r3
r4
IR
IP
Logic
CPU
3
b
2
5

33. Running the Program
a
c
2
5
3
Memory
Load a into r1
Load b into r3
r2 r1 + r3
Store r2 into c
2005
2006
2007
2008
2008
Store r2 into c
r1
r2
r3
r4
IR
IP
Logic
CPU
3
b
2
5

34. Putting it all together
Bus
CPU
RAM
Keyboard
Hard
Disk
Display
CD-ROM
•Computer has many parts, connected by a Bus:

35. Putting it all together
Bus
CPU
RAM
Keyboard
Hard
Disk
Display
CD-ROM
•The RAM is the computer’s main memory.
•This is where programs and data are stored.

36. Putting it all together
Bus
CPU
RAM
Keyboard
Hard
Disk
Display
CD-ROM
•The CPU goes in a never-ending cycle, reading
instructions from RAM and executing them.

37. Putting it all together
•This cycle is orchestrated by the Control Unit
in the CPU.
Memory Registers
Register 0
Register 1
Register 2
Register 3
Instruction Register
Instr. Pointer (IP)
Arithmetic
/ Logic
Unit
Control Unit
(State Machine)

38. Back to the Control Unit
•It simply looks at where IP is pointing, reads the
instruction there from RAM, and executes it.
Memory Registers
Register 0
Register 1
Register 2
Register 3
Instruction Register
Instr. Pointer (IP)
Arithmetic
/ Logic
Unit
Control Unit
(State Machine)

39. Putting it all together
•To execute an instruction, the Control Unit uses
the ALU plus Memory and/or the Registers.
Memory Registers
Register 0
Register 1
Register 2
Register 3
Instruction Register
Instr. Pointer (IP)
Arithmetic
/ Logic
Unit
Control Unit
(State Machine)

40. Clock rate
•In computing, the clock rate or clock speed
typically refers to the frequency at which
the clock generator of a processor can
generate pulses, which are used to
synchronize the operations of its
components, and is used as an indicator of
the processor's speed.

41. Programming

42. The Instruction Set:
a Critical Interface
instruction set
software
hardware

43. Instruction Set Architecture
•A very important abstraction:
–interface between hardware and low-level software
–standardizesinstructions, machine language bit patterns, etc.
–advantage: allowsdifferent implementations of the same architecture
–disadvantage: sometimes prevents adding new innovations
•Modern instruction set architectures:
–80x86/Pentium/K6, PowerPC, DEC Alpha, MIPS, SPARC, HP

44. What is Computer Architecture?
Easy Answer
Computer Architecture =
Instruction Set Architecture +
Machine Organization

45. I/O systemInstars. Set Proc.
Compiler
Operating
System
Application
Digital Design
Circuit Design
Instruction Set
Architecture
Firmware
Datapath & Control
Layout
What is Computer Architecture?
Better (More Detailed) Answer

46. Forces on Computer Architecture
Computer
Architecture
Technology Programming
Languages
Operating
Systems
History
Applications