INTEL387TMDX データシートの表示（PDF） - Intel
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INTEL387TMDX Datasheet PDF : 41 Pages
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Intel387TM DX MATH COPROCESSOR
Intel386TM DX Microprocessor Registers
GENERAL REGISTERS
31
15
0
EAX
AX
AH AL
EBX
BX
BH BL
ECX
CX
CH CL
EDX
DX
DH DL
SEGMENT REGISTERS
15
0
CS
SS
DS
ES
FS
GS
ESI
SI
31
0
EDI
DI
EIP
EFLAGS
EBP
BP
ESP
SP
l
Intel387TM DX MCP Data Registers
l
Tag
l
Field
l
79 78 64 63
0
10
l R0 Sign Exponent
Significand
l
l
R1
l R2
l R3
l
l
R4
l R5
l R6
l
l
R7
l
l 15
0 47
0
ll Control Register Instruction Pointer (in i386TM DX CPU)
l Status Register
Data Pointer (in i386TM DX CPU)
l Tag Word
l
l
l
l
l
Figure 1 1 Intel386TM DX Microprocessor and Intel387TM DX Math Coprocessor Register Set
1 0 FUNCTIONAL DESCRIPTION
The Intel387TM DX Math Coprocessor provides
arithmetic instructions for a variety of numeric data
types in Intel386TM DX Microprocessor systems It
also executes numerous built-in transcendental
functions (e g tangent sine cosine and log func-
tions) The Intel387 DX MCP effectively extends the
register and instruction set of a Intel386 DX Micro-
processor system for existing data types and adds
several new data types as well Figure 1 1 shows the
model of registers visible to programs Essentially
the Intel387 DX MCP can be treated as an additional
resource or an extension to the Intel386 DX Micro-
processor The Intel386 DX Microprocessor togeth-
er with a Intel387 DX MCP can be used as a single
unified system
The Intel387 DX MCP works the same whether the
Intel386 DX Microprocessor is executing in real-ad-
dress mode protected mode or virtual-8086 mode
All memory access is handled by the Intel386 DX
Microprocessor the Intel387 DX MCP merely oper-
ates on instructions and values passed to it by the
Intel386 DX Microprocessor Therefore the Intel387
DX MCP is not sensitive to the processing mode of
the Intel386 DX Microprocessor
In real-address mode and virtual-8086 mode the In-
tel386 DX Microprocessor and Intel387 DX MCP are
completely upward compatible with software for
8086 8087 80286 80287 real-address mode and
Intel386 DX Microprocessor and 80287 Coproces-
sor real-address mode systems
In protected mode the Intel386 DX Microprocessor
and Intel387 DX MCP are completely upward com-
patible with software for 80286 80287 protected
mode and Intel386 DX Microprocessor and 80287
Coprocessor protected mode systems
The only differences of operation that may appear
when 8086 8087 programs are ported to a protect-
ed-mode Intel386 DX Microprocessor and Intel387
DX MCP system (not using virtual-8086 mode) is in
the format of operands for the administrative instruc-
tions FLDENV FSTENV FRSTOR and FSAVE
These instructions are normally used only by excep-
tion handlers and operating systems not by applica-
tions programs
The Intel387 DX MCP contains three functional units
that can operate in parallel to increase system per-
formance The Intel386 DX Microprocessor can be
transferring commands and data to the MCP bus
control logic for the next instruction while the MCP
floating-point unit is performing the current numeric
instruction
5
5
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