x86 vs i386 vs Other Processor Terms

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  • DevynCJohnson
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    • @devyncjohnson

    It may be helpful to know that 32-bit, x86, i386, IA-64, etc. do not quite mean the same thing. It may help to have a thorough understanding of these various processor terms and their meaning.

    32-bit and 64-bit

    Memory addresses, buses, registers, etc. can be one of many sizes. The sizes are measured in bits (a single binary digit of "0" or "1"). Many processors in the early 2000's are either 32-bit or 64-bit. A 64-bit processor can support much more resources than a 32-bit CPU due to the larger amount of accessible addresses that can be represented. For instance, 32-bit systems are limited to 4GB or RAM due to the fact that 32 bits (digits) of binary numbers can only reference up to 4 billion bytes (4GB). To calculate this limit, use the equation "2bits" or "2^bits". Therefore, we can see that 2^32 = 4294967296. Then, 4294967296 divided by 1000000000 (one billion) will convert bytes to gigabytes. Finally, the answer is 4.2GB.

    x86 and x86-64

    x86 refers to processors that are compatible with the Intel 8086 processor which is a 16-bit CPU. Any processor that is compatible with the 8086 (including 32-bit CPUs) can be referred to as an x86 processor. However, the term "x86" is often used to refer to 32-bit processors that are 8086 compatible.

    x86-64 is a 64-bit form of the x86 CPU structure. AMD64 processors and many 64-bit Intel CPUs are x86-64 processors.

    IA-32 and IA-64

    IA-32 (Itanium Architecture) is a term for 32-bit x86 processors.

    IA-64 (Itanium Architecture) refers to 64-bit processors that are compatible with the Itanium processor. Keep in mind that x86-64 and IA-64 are not the same thing. They are both 64-bit CPUs. x86-64 is a generic term for processors with the 64-bit extension to x86.

    i386 and Other Intel Processors

    The "i" stands for "Intel". So, "i386" refers to the Intel 80386 processor. The difference between the i386, i486, i586, and others lies in the performance and features. Obviously, the i586 is better (faster) than the i386. All of the i*86 processors are x86 CPUs. Therefore, they are all 32-bit processors.

    • Intel 80386 = i386
    • Intel 80586 = i586
    • x86 = i386, i486, and i586

    Typically, an operating system that is designed for the i386 processor (like Linux) will work on an i486 or i586. However, be aware that exceptions may apply to some systems.

    The Intel 8080 is an 8-bit processor and the Intel 8086 is a 16-bit processor.

    x87 and i387

    The x87 is a form of the x86 with additional float-point features. The Intel 80387 (0r i387) is a 32-bit processor with extra float-point features. The Pentium II, III, and 4 are examples of x87 processors.

    Further Reading

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