INTEL387TMDX データシートの表示（PDF） - Intel

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INTEL387TMDX

Intel387™ DX MATH COPROCESSOR

Intel 

Intel387TM DX MATH COPROCESSOR

2 0 PROGRAMMING INTERFACE

The MCP adds to the Intel386 DX Microprocessor

system additional data types registers instructions

and interrupts specifically designed to facilitate high-

speed numerics processing To use the MCP re-

quires no special programming tools because all

new instructions and data types are directly support-

ed by the Intel386 DX CPU assembler and compilers

for high-level languages All 8086 8088 develop-

ment tools that support the 8087 can also be used

to develop software for the Intel386 DX Microproc-

essor and Intel387 DX Math Coprocessor in real-ad-

dress mode or virtual-8086 mode All 80286 devel-

opment tools that support the 80287 can also be

used to develop software for the Intel386 DX Micro-

processor and Intel387 DX Math Coprocessor

All communication between the Intel386 DX Micro-

processor and the MCP is transparent to applica-

tions software The CPU automatically controls the

MCP whenever a numerics instruction is executed

All physical memory and virtual memory of the CPU

are available for storage of the instructions and op-

erands of programs that use the MCP All memory

addressing modes including use of displacement

base register index register and scaling are avail-

able for addressing numerics operands

Section 6 at the end of this data sheet lists by class

the instructions that the MCP adds to the instruction

set of the Intel386 DX Microprocessor system

2 1 Data Types

Table 2 1 lists the seven data types that the Intel387

DX MCP supports and presents the format for each

type Operands are stored in memory with the least

significant digit at the lowest memory address Pro-

grams retrieve these values by generating the low-

est address For maximum system performance all

operands should start at physical-memory address-

es evenly divisible by four (doubleword boundaries)

operands may begin at any other addresses but will

require extra memory cycles to access the entire op-

erand

Internally the Intel387 DX MCP holds all numbers in

the extended-precision real format Instructions that

load operands from memory automatically convert

operands represented in memory as 16- 32- or 64-

bit integers 32- or 64-bit floating-point numbers or

18-digit packed BCD numbers into extended-preci-

sion real format Instructions that store operands in

memory perform the inverse type conversion

2 2 Numeric Operands

A typical MCP instruction accepts one or two oper-

ands and produces a single result In two-operand

instructions one operand is the contents of an MCP

register while the other may be a memory location

The operands of some instructions are predefined

for example FSQRT always takes the square root of

the number in the top stack element

6

6

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