Intel 80486

The exposed die of an Intel 80486DX2 microprocessor.

The 486DX2 architecture.

Intel i486 (sering disebut 486 or 80486) adalah suatu 32-bit scalar Intel CISC microprocessors yang merupakan bagian dari keluarga prosesor mikroIntel x86. i486's merupakan penerus kesuksesan dari Intel 80386.Prosesor mikro 486 pertama kali diperkenalkan pada tahun 1989. i486 sering disebut tanpa tambahan kata depan 80, karena peraturan pengadilan melarang nomro trademarking (seperti 80486).Intel menghapus nama dasar penomoran dengan menganti i486 – sebagai Pentium processor.

Dari sisi penilaian perangkat lunak,dalam instruction set dari keluarga i486 sangatlah mirip dengan sebelumnya, Intel 80386, dimana hanya memberikan sedikit instructions tambahan.

Dari sisi penilaian perangkat keras, bagaimanapun, arsitektur dari i486 merupakan kemajuan besar.dimana terdapat satu kesatuan dari instuksi dan data cache dalam satu chip , suatu chip pilihan floating-point unit (FPU) ( DX model saja), dan suatu ditingkatkan bus dalam menghubungkan unit. Sebagai tambahan, di bawah kondisi-kondisi optimal, inti pengolah dapat mendukung suatu pelaksanaan instruksi dalam satu satuan putaran waktu (clock cycle) . Peningkatan ini menghasilkan suatu penggandaan performance dari Intel 80386 dalam wakut yang sama (clock rate). Bagaimanapun, beberapa model i486 low-end sangatlah lamban dibandingkan dengan kecepatan 386, terutama dengan 'SX' i486.

Perbedaan antara 80386 dan 80486

• Data/Instruction Cache -pada 8192-byte (8 kB) SRAM tertanam pada inti processor,dibuat untuk menyimpan penggunaan instruksi biasa.386 mendukung off-chip cache,tetapi ini sangatlah lambat.
• Pipelining - ini mengijinkan processor untuk melakukan LocateFetchExecute setiap putaran waktu (clock cycle). Pipeline merupakan penganti informasi pelaksanaan alur instruksi yang dibutuhkan dari dua putaran waktu sebelumnya.tempatnya haruslah diberikan pada fatch berikutnya,fetch haruslah diberikan pada pelaksanaan berikutnya.386 perlu melakukan instruksi secara terpisah.
• Peningkatan performance MMU
• Terintergrasi FPU- (hanya model DX saja) penambahan fungsi matematika.

486 mempunyai sebua 32-bit data bus dan sebuah 32-bit address bus.ini diperlukan bagi 30-pin SIMMs atau 72-pin SIMM. Pengalamatan bus 32-bit terbatas samapi 4 GB dari RAM.

Pimpinan project untuk 80486 adalah Patrick Gelsinger.

pada Mei 2006 Intel mengumumkan bahwa produksi dari 80486 akan berhenti di ahir bulan September 2007.[1] walaupun chip ini telah lama menjadi sangat penting untuk perangkat PC, Intel akan melanjutkan produksi untuk digunakan dalam embedded systems.

Model-model

An Intel 80486DX-33 microprocessor

There are several suffixes and variants including:

• Intel 80486SX - a i486DX with its FPU disabled, although the earlier variants were simply normal i486s with defective FPUs. In later versions, the FPU was removed from the die to reduce its area and thus reduce cost.
• Intel 80486DX - same as above, with a working FPU.
• Intel 80486DX2 - the internal processor clock runs at twice the clock rate of the external bus clock.
• Intel 80486SX2 - same as the i486DX2, but with the FPU disabled.
• Intel 80486SL - i486SX with power conservation circuitry. Mainly for use in portable computers.
• Intel 80486SL-NM - i486SX with power conservation circuitry; SL enhanced suffix, denotes a i486 with special power conservation circuitry similar to that in the i486SL processors.
• Intel 80487 - i486DX with a slightly different pinout for use in i486SX systems as a FPU.
• Intel 80486 OverDrive - i486SX, i486SX2, i486DX2 or i486DX4. Marked as upgrade processors, some models had different pinouts or voltage handling abilities from 'standard' chips of the same speed stepping.
• Intel 80486DX4 - designed to run at triple clock rate (not quadruple as often believed; the DX3, which was meant to run at 2.5x the clock speed, was never released).

Internal clock rates included 16, 20, 25, 33, 40, 50, 66, 75 and 100 MHz, although the 100 MHz versions could be somewhat unstable. The 486DX2 66 MHz was the most widespread high-end 486 chip, while more powerful iterations such as the OverDrive and DX4 were less used in favour of the succeeding Pentium. The only 486 that ran a 50 MHz bus, the 486DX 50 MHz chip, had compatibility problems with boards and components because of this high bus speed requirement. 486DX 50 MHz was a rather unpopular chip and was quickly replaced by the clock-doubled 486 DX2 chips which ran the bus at half of the CPU clock speed.

Persaingan lain

486 compatible processors have been produced by other companies such as IBM, Texas Instruments, AMD, Cyrix, and Chips and Technologies. Some are almost exact duplicates in specifications and performance, some are not. The 486 was, however, covered by many of Intel's 386 patents as well as some of its own. Intel and IBM have broad cross-licenses of these patents, and AMD was granted rights to the relevant patents in the 1995 settlement of a lawsuit between the companies.[2]

Dasar

With regards to the 486 system platform, early 486 machines were equipped with only 16-bit and 8-bit ISA slots. Later motherboards combined ISA with the high-speed VESA Local Bus (VLB), primarily for video cards and hard drive controllers. The final 486 boards came equipped with PCI and ISA, and sometimes VLB as well (though in this configuration VLB suffered performance-wise). Bus speed was determined by multipliers for ISA, but PCI and VLB bus clocks were often equal to the clock of the 486 bus (some boards had multipliers for these as well).

Later 486 boards also supported Plug-and-play, the Microsoft technology that began as a part of Windows 95 designed to make component installation easier for consumers.

Lihat pula

• List of Intel microprocessors
• Motorola 68040, although not compatible, often considered the Motorola equivalent to the Intel 80486 in terms of performance.

Referensi

Artikel ini berdasarkan bahan-bahan dari Free On-line Dictionary of Computing, yang diberi lisensi GFDL.

Pranala luar

• http://users.erols.com/chare/486.htm
• Intel 80486 images and descriptions at cpu-collection.de
• CPU-INFO: 80486, indepth processor history