Intel 80386DX

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Intel 80386DX

The Intel 80386DX was the first true 32-bit processor used on the PC platform. Its internal register size was increased to 32 bits, and its data and address buses were as well, doubling data path width to the processor and increasing addressable memory to 4 GB theoretical. The 80386 family of chips offered more performance than the 80286s they replaced, largely through processor speed increases. The 386 did not offer the very large improvements over the 286 that the 286 did over the 8088.

The 386DX's increased power and the improved processor modes it offered (including full protected mode and virtual real modes) spurred the introduction of GUI-based operating systems on the PC, such as Microsoft Windows (although they are still quite slow on 386 chips). The instruction set of the 386 has set the standard for what is now called "x86" and hasn't changed very much since it was introduced. The 80386DX was the first to use pipelining to allow much improved processor performance through the use of much higher clock frequencies.

Invented by Intel, the 386 was also "cloned" by AMD and Cyrix. These are very good copies with no real compatibility problems. Intel only produced the 386DX up to 33 MHz (presumably to prevent overlapping into the 486's performance range) while AMD and Cyrix produced a 40 MHz version as well. This latter chip produced very good performance (for the time), comparable to many lower-end 486s. They are still however obsolete by today's standards, of course.

Look here for an explanation of the categories in the processor summary table below, including links to more detailed explanations.

General Information	Manufacturer	Intel			Intel, AMD, Cyrix	AMD, Cyrix
	Family Name	80386DX
	Code name	--
	Processor Generation	Third
	Motherboard Generation	Third
	Version	80386DX -16	80386DX -20	80386DX -25	80386DX -33	80386DX -40
	Introduced	Oct. 1985	Feb. 1987	April 1988	April 1989	!?
	Variants and Licensed Equivalents	!?
Speed Specifications	Memory Bus Speed (MHz)	16	20	25	33	40
	Processor Clock Multiplier	1.0
	Processor Speed (MHz)	16	20	25	33	40
	"P" Rating	--
Benchmarks	iCOMP Rating	~29	~38	49	68	~85
	iCOMP 2.0 Rating	--
	Norton SI	~15	~20	~25	35	~43
	Norton SI32	!?
	CPUmark32	--
Physical Characteristics	Process Technology	CMOS
	Circuit Size (microns)	originally 1.5, now 1.0
	Die Size (mm^2)	!?
	Transistors (millions)	0.275
Voltage, Power and Cooling	External or I/O Voltage (V)	5
	Internal or Core Voltage (V)	5
	Power Management	None
	Cooling Requirements	None
Packaging	Packaging Style	132-Pin PGA
	Motherboard Interface	132-Pin Socket
External Architecture	Data Bus Width (bits)	32
	Maximum Data Bus Bandwidth (Mbytes/sec)	63.6	76.3	95.4	127.2	152.6
	Address Bus Width (bits)	32
	Maximum Addressable Memory	4 GB
	Level 2 Cache Type	None
	Level 2 Cache Size	--
	Level 2 Cache Bus Speed	--
	Multiprocessing	No
Internal Architecture	Instruction Set	x86
	MMX Support	No
	Processor Modes	Real, Protected, Virtual Real
	x86 Execution Method	Native
Internal Components	Register Size (bits)	32
	Pipeline Depth (stages)	4
	Level 1 Cache Size	None
	Level 1 Cache Mapping	--
	Level 1 Cache Write Policy	--
	Integer Units	1
	Floating Point Unit / Math Coprocessor	Optional 80387 Coprocessor
	Instruction Decoders	1
	Branch Prediction Buffer Size / Accuracy	None
	Write Buffers	None
	Performance Enhancing Features	None

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