Computer Science · Ch 1 — Computer System
Microprocessors
Microprocessors
In earlier days, a computer's CPU occupied a large room or several cabinets. Advances in technology have shrunk that same functionality onto a single microchip. A processor (CPU) implemented on a single microchip is called a microprocessor — and since nowadays almost every CPU is built this way, the terms CPU and microprocessor are used synonymously for practical purposes.
What a microprocessor is
A microprocessor is a small-sized electronic component inside a computer that carries out the tasks involved in data processing as well as arithmetic and logical operations. A modern microprocessor is built on an integrated circuit comprising millions of tiny components — resistors, transistors and diodes.
Over time, microprocessors have evolved along three consistent trends:
- increasing processing capability,
- decreasing physical size, and
- reducing cost.
Currently available microprocessors can process millions of instructions per millisecond.
Generations of microprocessors
Since their inception in the early 1970s, microprocessors have passed through five generations, distinguished by their chip technology, word size, memory capacity, clock speed and core count. Table 1.2 summarises them:
| Generation | Era | Chip type | Word size | Maximum memory size | Clock speed | Cores | Examples |
|---|---|---|---|---|---|---|---|
| First | 1971–73 | LSI | 4 / 8 bit | 1 KB | 108 KHz – 200 KHz | Single | Intel 8080 |
| Second | 1974–78 | LSI | 8 bit | 1 MB | Up to 2 MHz | Single | Motorola 6800, Intel 8085 |
| Third | 1979–80 | VLSI | 16 bit | 16 MB | 4 MHz – 6 MHz | Single | Intel 8086 |
| Fourth | 1981–95 | VLSI | 32 bit | 4 GB | Up to 133 MHz | Single | Intel 80386, Motorola 68030 |
| Fifth | 1995 till date | SLSI | 64 bit | 64 GB | 533 MHz – 34 GHz | Multicore | Pentium, Celeron, Xeon |
(The examples column lists only a few prominent chips of each generation.)
Reading the table down any column shows the growth story: word size climbed from 4 bits to 64 bits, addressable memory from 1 KB to 64 GB, clock speed from the kilohertz range to tens of gigahertz, and the fifth generation added multiple cores on one chip. …
| Generation | Era | Chip type | Word size | Maximum memory size | Clock speed | Cores | Example* |
|---|---|---|---|---|---|---|---|
| First | 1971-73 | LSI | 4 / 8 bit | 1 KB | 108 KHz-200 KHz | Single | Intel 8080 |
| Second | 1974-78 | LSI | 8 bit | 1 MB | Upto 2 MHz | Single | Motorola 6800 Intel 8085 |
| Third | 1979-80 | VLSI | 16 bit | 16 MB | 4 MHz - 6 MHz | Single | Intel 8086 |
| Fourth | 1981-95 | VLSI | 32 bit | 4 GB | Upto 133 MHz | Single | Intel 80386 Motorola 68030 |