1. Computer Architecture
ECE 4801
Berk Sunar

2. Outline Brief Overview How is a computer program executed?
Computer organization
Roadmap for this class

3. Things You Learn in this Course
How computers work; the basic foundation
How to analyze their performance (and how not to)
Key technologies determining the performance of modern processors
Datapath Design
Pipelining
Cache Systems
Memory Hierarchy
I/O
Multiprocessors

4. Instruction Set Architecture
Important abstraction
Interface between hardware and low-level software
Or features available to programmers
instructions set architecture (ISA)
e.g. does the processor have an multiply instruction?
instruction encoding
Data representation
I/O mechanism.
addressing mechanism
Modern instruction set architectures:
80x86/Pentium/K6, PowerPC, DEC Alpha, MIPS, SPARC, HP, ARM.

5. Computer Organization
Computer Organization is how features are implemented in hardware
Transparent to programmers
Different implementations are possible for the same architecture (affects performance/price)
Determines how memory, CPU, peripherals, busses are interconnected and how control signals routed.
Has HUGE impact on performance.
Performance of the organization is usually application dependent. (e.g. I/O intensive, computation intensive, memory bound etc.)

6. How to Program a Computer?
A simple but universal interface
Machine Code (binary images)
Assembly language
Uses mnemonics that map directly to ISA e.g. addw, lb, jmp etc.
More readable than machine languages
Error prone but excellent for low-level optimization
High-level languages
E.g. C/C++, Pascal, Fortran, Java, C#
Much easier to use and program
Promotes code portability
Not as efficient as custom assembly

7. Processing a C Program High-level language program (in C)
swap:
muli $2, $5, 4 add $2, $4, $2 lw $15, 0($2) lw $16, 4($2) sw $16, 0($2) sw $15, 4($2) jr $31
Assembly language program for MIPS
swap (int v[], int k){ int temp; temp = v[k]; v[k] = v[k+1]; v[k+1] = temp; }
C compiler
Binary machine
language program for MIPS
Assembler

8. Functions of a Computer
Data processing , e.g. sort entries of a spreadsheet
Data storage, e.g. personal files, applications, movies, music etc.
Data movement, e.g. play a music file, display a picture
Control, (applies to all examples above)

9. Functions of a Computer
source & destination of data
data movements
apparatus
Control
mechanism
Data processing
facility
Data storage
facility

10. Five Classic Components
Computer
Processor
Memory
Input
Datapath
Control
Output
System Interconnection

11. Motherboard USB 2.0 SIMM Sockets Processor PCI Card Slots IDE
Sound
Parallel/Serial
PS/2
connectors
SIMM
Sockets
Processor
PCI
Card
Slots
IDE
Connectors

12. Inside the Processor Chip
Instruction
Cache
Control
branch
prediction
Data
Cache
Bus
integer
datapath
floating-point
datapath

13. CPU Cache Memory Registers ALU Control Unit Internal CPU
interconnection
CPU

14. Memory Nonvolatile: Volatile How about solid state drives? ROM
Hard disk, floppy disk, magnetic tape, CDROM, USB Memory
Flash memory
Volatile
DRAM used usually for main memory
SRAM used mainly for on-chip memory such as register and cache
DRAM is much cheaper than SRAM
SRAM is much faster than DRAM
How about solid state drives?

15. DRAM and Processor Characteristics

16. Solutions to Memory Problems
Increase number of bits retrieved at one time
Make DRAM “wider” rather than “deeper”
Change DRAM interface
Cache
Reduce frequency of memory access
More complex cache and cache on chip
Increase interconnection bandwidth
High speed buses
Hierarchy of buses

17. Computer Networks Very essential aspect of computer systems
Communication
Resource sharing
Remote access
Ethernet is the most popular LAN
Range is limited to 1 kilometer
10/100 Mbit/s
Wide Area Networks (WAN)
Cross continents and backbone of the Internet

18. Roadmap Performance issues Instruction set of MIPS Arithmetic and ALU
Constructing a processor to execute our instructions (datapath design)
Pipelining
Memory hierarchy: caches and virtual memory
I/O