CPUs have gone through many changes through the short years since Intel came out with the first one. IBM chose Intel’s 8088 processor for the brains of the first PC. This choice by IBM is what made Intel the de facto leader of the CPU market. It remains the leader of microprocessor development. It usually come out with the new ideas first. Then companies such as AMD and Cyrix come in with their versions, usually with some minor improvements, and slightly faster.
Intel processors have gone through five generations. A sixth is taking hold. The first four generations took on the “8” as the series name, which is why the technical types refer to this family of chips as the 8088, 8086, and 80186. This goes right on up to the 80486, or just 486. Then came along the Pentium. Intel went off and changed the name on this one. Some guys, though, call it the P5, or a 80586. Anyway, the higher the chip number, the more powerful the chip is, and the more costly.
Next is a list and brief description of the processors leading up to today’s fast computers. Knowing the internal workings of a CPU is pointless unless you plan on building one, so if you want more detailed info, download the data sheets on the processors. They’re in PDF format, so you’ll need the Acrobat Reader to read them.
The following chips are the dinosaurs of the computer world.
- Intel 8086 (1978)
This chip was skipped over for the original PC, but was used in a few later computers that didn’t amount to much. It was a true 16-bit processor and talked with its cards via a 16 wire data connection.
- Intel 8088 (1979)
This is the chip used in the first PC. It was 16-bit, but it talked to the cards via a 8-bit connection. It ran at a whopping 4 MHz and could address only 1 MB of RAM.
- NEC V20 and V30 (1981)
Clones of the 8088 and 8086. Supposedly about 30% faster than the Intel originals.
- Intel 80186
The 186 was a popular chip. Many versions have been developed in its history. Buyers could choose from CHMOS or HMOS, 8-bit or 16-bit versions, depending on need. A CHMOS chip could run at twice the clock speed and at one fourth the power of the HMOS chip. In 1990, Intel came out with the Enhanced 186 family. They shared a 1-micron core design and ran at about 25MHz at 3 volts.For more information on the 80186 Intel chip:
- Intel 80286 (1982)
A 16-bit processor capable of addressing up to 16 MB of RAM. This chip is able to work with virtual memory. What is that? See Memory. The 286 was the first “real” processor. It introduced the concept of protected mode. This is the ability to multitask, having different programs run separately but at the same time. This ability was not taken advantage of by DOS, but later Operating Systems, such as Windows, could play with this new feature. This chip was used by IBM in its Advanced Technology PC (AT). It ran at 6 MHz, but later editions of the chip ran as high as 20 MHz. These chips are considered paperweights today, but many still use them.
- Intel 386 (1988)
This chip started it all. With this chip, PCs began to be more useful than boat anchors. The 386 was the first 32-bit processor for PCs. It could, as a result, crunch twice as much data on each clock cycle and it could play around with 32-bit cards. It can talk to as much as 4 GB of real memory and 64 TB of virtual memory. This little badboy could also team up with a math coprocessor, called the 80387. It could also use processor cache, all 16 bytes of it.The reduced version of this chip is the 386SX. This is a low-fat chip, cheaper to make. It talked with the cards via a 16-bit path. 386s range in speed from 12.5MHz to 33MHz.386 chips were designed to be user friendly. All chips in the family were pin-for-pin compatible and they were binary compatible with the previous 186 chips, meaning that users didn’t have to get new software to use it. Also, the 386 offered power-friendly features such as low voltage requirements and System Management Mode (SMM) which could power down various components to save power.Overall, this was a big step for chip development. It set the standard that many later chips would follow. It offered a simple design which developers could easily design for.For a little more information on the 386:
- Intel 486 (1991)
This was the next generation processor. It brought the brains of a 386 together with an internal math coprocessor–plus it was much faster. This chip has been pushed to 120 MHz and is still in wide use today.The first member of the 486 family was the 486SX. It was very power efficient and performed well for the time. The efficient design led to new packaging innovations. The 486SX came in a 176 lead Thin Quad Flat Pack (TQFP) package and was about the thickness of a quarter.The next members of the 486 family were the DX2s and DX4s. Their speeds were obtained with speed-multiplier technology, which enabled the chip to operate at clock cycles greater than that of the bus. They also introduced the concept of RISC. Reduced instruction set chips(RISC) do just a few things, but really fast. This made this chip more efficient and set it apart from the older x86 chips. The DX2 offered 8 KB of write-through cache and the DX4 offered 16 KB. This cache helps the chip maintain its one clock cycle per instruction operation, through the use of RISC.It had SX and DX versions. Both were completely 32-bit, but the SX lacks the math coprocessor. Nevertheless, the SX version is roughly twice as fast as the 386. (Actually, the math coprocessor in the SX is there, just disabled for marketing purposes, I’m sure.)More information on the 486 processor:
- Intel486 Processor Reference Information
- For more technical design information on the chip, see Embedded Intel Architecture
- High Performance 486 Processors
- 486SX Datasheet
- 486DX2 Datasheet
- 486DX4 Datasheet
Intel brought the PC to the 64-bit level with the Pentium Processor in 1993. It has 3.3 million transistors and performs at 100 million instructions per second(MIPS).
The Pentium family includes the 75/90/100/120/133/150/166/200 clock speeds. It is compatible with all of the older OSes including DOS, Windows 3.1, Unix and OS/2. Its superscalar design can execute two instructions per clock cycle. The separate caches and the pipelined floating point unit increase its performance beyond the x86 chips. It has SL power management features and has the ability to work as a team with another Pentium. The chip talks over a 64-bit bus to its cards. It has 273 pins connecting it to the motherboard. Internally, though, it’s really two 32-bit chips chained together that split the work. The chip comes with 16 K of built-in cache.
This chip, although fast, gets really hot, so the use of a CPU fan is required. Rather recently, Intel has released more efficient versions of the chip that operate at 3.3 volts, rather than the usual 5 volts. This has reduced the heat somewhat.
Here are some extra little things:
The processor has a burst mode that loads 256-bit chunks of data into the data cache in a single clock cycle. It can transfer data to the memory at up to 528 MB/Sec. Also, Intel took it upon themselves to hardwire several heavily used commands into the chip. This bypasses the typical microcode library of commands. It also has a built-in self-test that operates upon resetting.
For more information on the processor, consult the following links:
- Pentium Processor Manuals
- Pentium Processor Performance Brief
- Application Notes
- Pentium Processor Performance Indicators
- In the News
- Pentium Pro Processor On-Line Introduction
Overdrive chips are generally known as turbochargers for older chips. They can be a cost-effective upgrade between your old chip and the new-fangled stuff. Intel is really the king of overdrives, having produced a line of them for the 486 machines and some for the Pentiums.
These chips basically allow the CPU to work at double the clock speed. Intel estimates that their overdrives can increase performance by 70%. They are not complete magic, though. The CPU still talks to its external cards at the same speed. So, in essence, you can have a fast thinking computer that talks real slow.
- The Dual 1 GHz Pentium III Myth - June 10, 2020
- Processor History - June 10, 2020
- SCSI - June 10, 2020