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The AMD Am486 DX Processor
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The Am486 is a 80486-class processors produced by AMD in the 1990s. Intel beat AMD to market by nearly four years, but AMD priced its 40 MHz 486 at or below Intel's price for a 33 MHz chip, offering about 20% better performance for the same price. Early AMD 486 chips were drop-in replacements for their Intel counterparts, but later AMD clock-doubled 486s ran at 3.3 volts instead of Intel's 5 volts, which limited their suitability as upgrade chips until third-party voltage adapters appeared on the market.
While the Am386 was primarily used by small computer manufacturers, the Am486DX, DX2, and SX2 chips gained acceptance among larger computer manufactuers, expecially Acer and Compaq, in the 1994 time frame.
AMD's higher clocked 486 chips provided superior performance to many of the early Pentium chips, especially the 60 and 66 MHz launch products. While equivalent Intel 80486DX4 chips were priced high and required a minor socket modification, AMD priced low. Intel's DX4 chips had twice the cache of the AMD chips, giving them a slight performance edge, but AMD's DX4-100 usually cost less than Intel's DX2-66.
The AMD Am5x86 was an enhanced Am486.
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Enhanced Am486, built around the standard AMD 486 core, incorporated write-back cache and enhanced power management features. These characteristics made them a good choice for reduced power consumption desktop systems and for the portable market segment. With clock-tripled performance speeds up to 120 MHz, these 3-V CPUs offered great price/performance value for both desktop and portable computers by providing power management and write-back enhanced features at no extra premium.
The enhanced Am486 microprocessors featured enhanced power management features, including SMM and clock control. These enhancements allow reduced power consumption during system inactivity. The SMM function is implemented with an industry standard two-pin interface. In write-back mode, frequently used data is stored in the high-speed internal cache and accessed continually from within until the data is modified, thus increasing the performance of the CPU. |
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The AMD 5x86 Processor
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Introduced in November 1995, the AMD 5x86 is a standard 486 processor with an internally-set multiplier of 4, allowing it to run at 133 MHz on systems without official support for clock-multiplied DX2 or DX4 486 processors. Like most of the later 486 parts, the 5x86 featured write-back L1 cache, and unlike all but a few, a generous 16 kilobytes rather than the more common 8KB.
Since having a clock multiplier of four was not part of the original Socket 3 design, AMD made the 5x86 look for a two times setting from the motherboard and interpret that as four times instead. In other words, to use the 5x86 you want to set the motherboard to the 2x setting. This will actually cause the 5x86 to run at 4x.
The combination of best-in-class clock speed and the write-back cache allowed the 5x86 to equal or slightly surpass an Intel Pentium 75 MHz processor in business application performance. Also, because it was based on a pure 486 design, it was compatible with older systems, something its slightly faster rival, the Cyrix 5x86, had trouble with. |
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