Differences between the 386 and 486
15.6 Differences From 8086 In general, V86 mode will correctly execute software designed for the 8086, 8088, 80186, and 80188. Following is a list of the minor differences between 8086 execution on the 80386 and on an 8086. Instruction clock counts. The 80386 takes fewer clocks for most instructions than the 8086/8088. There are several differences between the 8086 and the 80386. Two notable differences: 1.) the 8086 is a 16 bit computer, while the 80386 is a 32 bit computer, and 2.) the 8086 does not support.
The 80386 in80386 protected mode support all the software written for 80286 and 8086 to be executed under the control of memory management and protection abilities of 80386. The protected mode allows the use of additional instruction, addressing modes and capabilities of 80386.
* An 8 KB on-chip SRAM cache stores the most commonly used instructions and data (16 KB and/or write-back on some later models). The 386 had no such internal cache but supported a slower off-chip cache.Difference Between 8086 And 80386
* Tightly coupled pipelining allows the 486 to complete a simple instruction like ALU reg,reg or ALU reg,im every clock cycle. The 386 needed two clock cycles for this.
* Integrated FPU (disabled or absent in SX models) with a dedicated local bus gives faster floating point calculations compared to the i386+i387 combination.
* Improved MMU performance.
The 486 has a 32-bit data bus and a 32-bit address bus. This required either four matched 30-pin (8-bit) SIMMs or one 72-pin (32-bit) SIMM on a typical PC motherboard. The 32-bit address bus means that 4 GB of memory can be directly addressed.
The Intel project manager for the 80486 was Pat Gelsinger.
Difference Between 8085 And 8086 And 80386
In May 2006 Intel announced that production of the 80486 would cease at the end of September 2007. Although the chip had long been obsolete for personal computer applications, Intel had continued production for use in embedded systems.