Intel 80287, 80286 manual Overview of Numeric Processing, Fxam StackO assumed Examine

OVERVIEW OF NUMERIC PROCESSING

DOUBLE-PRECISION

WHETSTONE PERFORMANCE

(KOPS)

( 80286/80287 )

200	.-------...../
	( 8086/8087)
100

STACK TOP POINTER'"

19801983 YEAR INTRODUCED

G30108

Figure 1-1. Evolution and Performance of Numeric Processors

Table 1-1. Numeric Processing Speed Comparisons

	Approximate Performance Ratios:
Floatlng'PolntInstruction	8	MHz 80287 to
	8	MHz Protected Mode IAPX using E80287

FADD ST,ST (Temp Real)	Addition	1:	42
FDIV DWORD PTR (Single-Precision)	Division	1:266
FXAM (Stack(O) assumed)	Examine	1:139
FYL2X (Stack(O),(1) assumed)	Logarithm	1:	99
FPATAN (Stack(O) assumed)	Arctangent	1:153
F2XM1 (Stack(O) assumed)	Exponentiation	1:	41

Ease of Use

The 80287 NPX offers more than raw execution speed for computation-intensive tasks. The 80287 brii:.g3 the f!!ncticn::!lity ~nd power of Accurate numeric computation into the hands of the general user.

Like the 8087 NPX that preceded it, the 80287 is explicitly designed to deliver stable, accurate results when programmed using straightforward "pencil and paper" algorithms. The IEEE 754 standard specifically addresses this issue, recognizing the fundamental importance of making numeric compu- tations both easy and safe to use.

For example, most computers can overflow when two single-precision floating-point numbers are multi- plied together and then divided by a third, even if the final result is a perfectly valid 32-bit number.

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