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Central processing units are the brains behind any computer system.Introduction and overview of the Intel 80486SX Central Processing Unit.
 
Complete guide to Central Processing Units
Introductions Principles Of The CPU Evolution Of The CPU Overclocking
CPU Cooling Chipsets and Bus Types CPU Connectors Conclusions
Previous Page: The 80386SX CPU Next Page: The 80486DX Processor
Quick Specifications:
Processor Label: 80486SX # Of Transistors: 1,180,235
Generation: 4th Generation Cache Memory: 8 kb
Release Year: Sep.1991 - Sep. 1992 Memory Bus Speed: 16mhz - 33mhz
Data Bus Width: 32 bits Clock Speed Range: 16mhz - 33mhz
Address Bus Width: 32 bits    
More Information:
The Intel 80486DX Central Processing Unit CPU

Although fourth-generation processors were more about refinement than redesign, the Intel 80486 (normally abbreviated as 486) was another major leap forward in the race for speed. The additional power available in the 486 fueled tremendous growth in the software industry. Tens of millions of copies of Windows, and millions of copies of OS/2, have been sold largely because the 486 finally made the graphical user interface (GUI) of Windows and OS/2 a realistic option for people who work on their computers every day.

The 486 is a family of processors, consisting of DX, SX, and a number of other variations. Four main features make 486 processors roughly twice as fast as an equivalent MHz 386 chip:

  • Reduced instruction-execution time— A single instruction in the 486 takes an average of only two clock cycles to complete, compared to an average of more than four cycles on the 386.

  • Internal (Level 1) cache— The built-in cache has a hit ratio of 90%–95%, which describes how often zero-wait-state read operations occur. External caches can improve this ratio further.

  • Burst-mode memory cycles— A standard 32-bit (4-byte) memory transfer takes two clock cycles. After a standard 32-bit transfer, more data up to the next 12 bytes (or three transfers) can be transferred with only one cycle used for each 32-bit (4-byte) transfer. Thus, up to 16 bytes of contiguous, sequential memory data can be transferred in as little as five cycles instead of eight cycles or more. This effect can be even greater when the transfers are only 8 bits or 16 bits each.

  • Built-in (synchronous) enhanced math coprocessor (some versions)— The math coprocessor runs synchronously with the main processor and executes math instructions in fewer cycles than previous designs did. On average, the math coprocessor built into the DX-series chips provides two to three times greater math performance than an external 387 math coprocessor chip.

The 486 chip is about twice as fast as the 386 at the same clock rate. You can see why the arrival of the 486 rapidly killed off the 386 in the marketplace. The die for the 486 is shown in Figure1.1

Figure 1.1 - 486 processor die. Photograph used by permission of Intel Corporation
 
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This document will outline the basic steps neccessary to install a CPU. You will learn why thermal grease is needed to disipate heat from within a system and how to install A CPU heatsink and CPU fan properly in a desktop computer.
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How To Troubleshoot A Bad Central Processing Unit (CPU)
This document will outline basic troubleshooting steps you can complete when you suspect your CPU fails or the system cannot boot at all or you see no video output when your computer is first powered on.
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