INTEL387TMDX 查看數據表（PDF） - Intel

零件编号

产品描述 (功能)

生产厂家

INTEL387TMDX

Intel387™ DX MATH COPROCESSOR

Intel 

Intel387TM DX MATH COPROCESSOR

APPENDIX A

COMPATIBILITY BETWEEN

THE 80287 AND THE 8087

The 80286 80287 operating in Real-Address mode

will execute 8086 8087 programs without major

modification However because of differences in the

handling of numeric exceptions by the 80287 MCP

and the 8087 MCP exception-handling routines may

need to be changed

This appendix summarizes the differences between

the 80287 MCP and the 8087 MCP and provides

details showing how 8086 8087 programs can be

ported to the 80286 80287

1 The MCP signals exceptions through a dedicated

ERROR line to the 80286 The MCP error signal

does not pass through an interrupt controller (the

8087 INT signal does) Therefore any interrupt-

controller-oriented instructions in numeric excep-

tion handlers for the 8086 8087 should be delet-

ed

2 The 8087 instructions FENI FNENI and FDISI

FNDISI perform no useful function in the 80287 If

the 80287 encounters one of these opcodes in its

instruction stream the instruction will effectively

be ignored none of the 80287 internal states will

be updated While 8086 8087 containing these

instructions may be executed on the

80286 80287 it is unlikely that the exception-

handling routines containing these instructions

will be completely portable to the 80287

3 Interrupt vector 16 must point to the numeric ex-

ception handling routine

4 The ESC instruction address saved in the 80287

includes any leading prefixes before the ESC op-

code The corresponding address saved in the

8087 does not include leading prefixes

5 In Protected-Address mode the format of the

80287’s saved instruction and address pointers is

different than for the 8087 The instruction op-

code is not saved in Protected mode exception

handlers will have to retrieve the opcode from

memory if needed

6 Interrupt 7 will occur in the 80286 when executing

ESC instructions with either TS (task switched) or

EM (emulation) of the 80286 MSW set (TS e 1 or

EM e 1) If TS is set then a WAIT instruction will

also cause interrupt 7 An exception handler

should be included in 80286 80287 code to han-

dle these situations

7 Interrupt 9 will occur if the second or subsequent

words of a floating-point operand fall outside a

segment’s size Interrupt 13 will occur if the start-

ing address of a numeric operand falls outside a

segment’s size An exception handler should be

included in 80286 80287 code to report these

programming errors

8 Except for the processor control instructions all

of the 80287 numeric instructions are automati-

cally synchronized by the 80286 CPU the 80286

automatically tests the BUSY line from the

80287 to ensure that the 80287 has completed its

previous instruction before executing the next

ESC instruction No explicit WAIT instructions are

required to assure this synchronization For the

8087 used with 8086 and 8088 processors ex-

plicit WAITs are required before each numeric in-

struction to ensure synchronization Although

8086 8087 programs having explicit WAIT in-

structions will execute perfectly on the

80286 80287 without reassembly these WAIT in-

structions are unnecessary

9 Since the 80287 does not require WAIT instruc-

tions before each numeric instruction the

ASM286 assembler does not automatically gener-

ate these WAIT instructions The ASM86 assem-

bler however automatically precedes every ESC

instruction with a WAIT instruction Although nu-

meric routines generated using the ASM86 as-

sembler will generally execute correctly on the

80286 80287 reassembly using ASM286 may re-

sult in a more compact code image

The processor control instructions for the 80287

may be coded using either a WAIT or No-WAIT

form of mnemonic The WAIT forms of these in-

structions cause ASM286 to precede the ESC in-

struction with a CPU WAIT instruction in the iden-

tical manner as does ASM86

DATA SHEET REVISION REVIEW

The following list represents the key differences be-

tween this and the -003 versions of the Intel387TM

Math Coprocessor Data Sheet Please review this

summary carefully

1 Corrected typographical errors

2 Corrected clock ratio ‘‘PIN’’ name on Table 4 2c

to NUMCLK CPUCLK

A-1

41

Share Link: