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Computer Organization








A Brief History of Computer Organization


If computer architecture is a view of the whole design with the important characteristics visible to programmer, computer organization is how features are implemented with the specific building blocks visible to designer or constructor, such as control signals, interfaces, memory technology, etc. Computer architecture and organization are closely related, though not exactly the same.   

A stored program computer has the following basic units:

  • Processor-- center for manipulation and control

  • Memory – storage for instructions and data for currently executing programs

  • I/O system – controller which communicate with “ external” devices: secondary memory, display devices, networks

  • Data-path & control – collection of parallel wires, transmits data, instructions, or control signal

Computer organization defines the ways in which these components interconnected, and controlled. It is the capabilities and performance characteristics of those principal function units. Architecture can have a number of organizational implementations, and organization differs between different versions.  Such, all Intel x86 families share the same basic architecture, and IBM system/370 family share their basic architecture.

The history of Computer Organization: Computer architecture has progressed five generation: vacuum tubes, transistors, integrated circuits, and VLSI.  Computer organization has also made its historic progression accordingly. 

The advance of microprocessor (Intel)

  • 1977: 8080 – the first general purpose microprocessor, 8 bit data path, used in first personal computer
  • 1978: 8086 – much more powerful with 16 bit, 1mb addressable, instruction cache, prefetch few instructions
  • 1980: 8087 – the floating point coprocessor is added
  • 1982: 80286 – 24 Mbyte addressable memory space, plus instructions
  • 1985: 80386 – 32 bit, new addressing modes and support for multitasking
  • 1989 -- 1995:
    • 80486 – 25, 33, MHz, 1.2 M transistors, 5 stage pipeline, sophisticated powerful cache and instruction pipelining, built in math co-processor
    • Pentium – 60, 66 MHz, 3.1 M transistor, branch predictor, pipelined floating point, multiple instructions executed in parallel, first superscalar IA-32.
    • PentiumPro -- Increased superscalar, register renaming, branch prediction, data flow analysis, and speculative execution
  • 1885 – 1997: Pentium II – 233, 166, 300 MHz, 7.5 M transistors, first compaction of p6 micro- architecture, MMX technology, graphics video and audio processing
  • 1889: Pentium III – additional floating point instructions for 3D graphics
  • 2000: Pentium IV – Further floating point and multimedia enhancements
  • 1993 – 2000: Itanium /Itanium 2 – 733 MHz, 25 M transistor, 0,18 micron, 3 levels of cache, superscalar degree 6, first implementation of 64-bit Itanium architecture.

Evolution of Memory

  • 1970: RAM /DRAM, 4.77 MHz
  • 1987: FPM – fast page mode DRAM, 20 MHz
  • 1995, EDO – extended Data Output, which increases the read cycle between memory and CPU, 20, MHz
  • 1997- 1998: SDRAM – Synchronous DRAM, which synchronizes itself with the CPU bus and runs at higher clock speeds, PC66 at 66 MHz, PC100 at 100 MHz
  • 1999: RDRAM – Rambus DRAM, which DRAM with a very high bandwidth, 800 MHz
  • 1999-2000: SDRAM PC133 at 133 MHz, DDR at 266 MHz
  • 2001: EDRAM – Enhanced DRAM, which is dynamic or power-refreshed RAM, also know as cached DRAM

Major buses and their features: A bus is a parallel circuit that connects the major components of a computer, allowing the transfer of electric impulses form one connected component to any other.

  • VESA – video electronics Standard Association: 32 bit, relied on the 486 processor to function
  • ISA – Industry Standard Architecture: 8 bit or 16 bit with width 8 or 16 bits. 8.3 MHz speed, 7.9 or 15.9 bandwidth accordingly.
  • EISA – Extended Industry Standard Architecture: 32 bits, 8.3 MHz, 31.8 bandwidth, the attempt to compete with IBM’s MCA
  • PCI – Peripheral Component Interconnect: 32 bits, 33 MHz, 127.2 bandwidth
  • PCI –X: Up to 133 MHz bus speed, 64 bits bandwidth, 1GB/sec throughput
  • AGP – Accelerated Graphics Port: 32 bits, 66 MHz, 254,3 bandwidth

Major ports and connectors/interface:

  • IDE – Integrated Drive Electronics, also know as ATA, EIDE, Ultra ATA, Ultra DMA, most widely used interface for hard disks
  • PS/2 port – mini Din plug with 6 pins for a mouse and keyboard
  • SCSI – Small Computer System Interface, 80 – 640 Mbs, capable of handling internal/external peripherals
  • Serial Port – adheres to RS-232c spec, uses DB9 or DB25 connector, capable of 115kb.sec speeds
  • Parallel port – as know as printer port,  enhanced types: ECP – extended capabilities port, EPP – enhanced parallel port
  • USB – universal serial bus, two types: 1.0 and 2.0, hot plug-and-play, at 12MB/s, up to 127 devices chain. 2.0 data rate is at 480 bits/s.
  • Firewire – high speed serial port, 400 MB/s, hot plug-and-play, 30 times faster than USB 1.0

 Summary Table:




Instruction sets







micro coded




5 K- 500 K



Small on-chip



1 M – 64 M



Small on-chip



100 M - 5 B


Improved gate speeds and power/cooling

Small on-chip

 Computer technology has been through a significant progression:

Computer technology has been through a significant progression:

  • The logic: relay ΰ vacuum tubes ΰ single transistors ΰ SSI/MSI ΰ VLSI;

  • The registers: delay lines ΰ drum ΰ semiconductor;

  • The memory: delay line ΰ magnetic drum ΰ core ΰ SRAM ΰ DRAM;

  • The external storage: paper tape, cards ΰmagnetic drum ΰ magnetic disk


What will be the next technology driven, just like semiconductor and magnetic played in the past?

Last modified: 2004 December 5