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What is the difference betWeen a 286, 386, 486 and a Pentium?
Most Personal Computer are using Intel X86 instruction sets. As long as they are using the same instruction sets, They can perform the same job. That is, 386, 486, Pentium and many other types of processors are equally Well. The only differences betWeen them are the speed, and memory addressing capability. Although 086 and 286 are using the same X86 instruction set, hoWever, because of having some troubles on addressing the high memory, therefore, many programs are not able the run on these older processors.

What are the differences betWeen these processors?


Trade Name

Main features



640K RAM only.



Limited addressing to high memory.



Can address to high and extended memory.



386 + mathematics co-processor.



486 + Dual pipeline, total 64 bit.


Pentium Pro, II, III, Celeron

586 + RISC + Looping speculations. 135MHz internal system bus.



686 + 64 bit per pipeline. 200 MHz internal system bus

What is a pipeline?
Pipeline is the shift register where computation actually occurs?

What is RISC?
Reduced Instruction Set Computer. Instruction sets has different lengths. Shorter instruction sets are wasting the processing time. A RISC has built in decoder to arrange instructions to have equal length in order to reduce idling time.

What is looping speculations?
Computer did lots of iterations. These looping are very systematic and easily predictable. Smart processors can speculate them with 95% accuracy. If the prediction is wrong, the computer is smart enough to correct them.

What determine the speed of my computer?
Besides the CPU can affect the speed of your computer. The data bus system, access time of your hard drive, the buffer size, the amount and speed of memory, the configuration of your system, the operating system, the program itself, and many other factors can affect your speed.

What is data bus system?
Data bus is the channel in which data transfer betWeen peripherals. Data could travel betWeen CPU and the memory. Hard drive needs the bus to load data into the memory. The video display needs display information. Sound system needs sound data and so on. Because of different peripherals can operate on different speed limit, therefore, each computer could have several bus system.

If my computer has a 400 MHz CPU, does it mean my bus also operates at 400 MHz?
No, 400 MHz is the CPU internal core speed. Your bus speed is only 100 MHz, your UDMA and PCI bus are only 33MHz. Your ISA bus speed is only 6 MHz.

What is an Ultra IDE (UDMA)?
Ultra IDE can transfer data betWeen hard drive and memory on both the leading edge and falling edge of the clock, therefore, it can transfer data at twice the speed of a regular IDE.

What is SCSI?
Small Computer System Interface is a bus system that

What is a Crusoe computer?
The Crusoe processor is a flexible and efficient hardware-software hybrid that replaces millions of poWer-hungry transistors with software.

Would Crusoe computer replace the current design?
Crusoe computer is just emerging into the market. Its future is unknown. But one thing for sure is it can cause a big change in the portable computer design. If this type of CPU is applied on home computers, it can make a big drop in prices. Another beauty of it is poWer it off is not necessary. That is, no need to boot up.


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