
 15. ⥪  ࠡ⪨ 権  饩
          窮
----------------------------------------------------------------

 ணࠬ⮢ ன⢮ ࠡ⪨ 権  饩
窮  i486(TM) ।⠢   ⥫
ॣ஢, ⨯   .  ⠫쭮 ᠭ 
᫮  ᬮ  26.  ⮩  뢠
⮫쪮 ᫮ ॣ  ⨯ , 室騥  ⥪
 i486.

15.1 ᫮ ॣ
----------------------------------------------------------------

᫮ ॣ  i486 :

- ᥬ ⤥쭮 㥬 80-ࠧ來 ॣ஢,
  ࣠  ॣ஢ ⥪.

-  16-ࠧ來 ॣ,  ᮤঠ:

   ﭨ  ࠡ⪨ 権  饩 窮.

  ࠢ饥 ᫮  ࠡ⪨ 権  饩
  窮.

   ਧ.

- ⥫ 訡, 騥 :

   16-ࠧ來 ॣ஢, ᮤঠ ᥫ 
  ᫥ 樨  ࠭.

   32-ࠧ來 ॣ஢, ᮤঠ ᬥ饭 
  ᫥ 樨  ࠭.

   11-ࠧ來 ॣ, ᮤঠ饣  樨 
  ᫥   ࠡ⪨ 権  饩
  窮,  ਭ饩   ࠢ.

 ᫮   i486 ᭮뢠  ᮤঠ
 ॣ஢  ࠡ⪨ 権  饩 窮.

15.1.1 ஢ ⥪  ࠡ⪨ 権 
       饩 窮
----------------------------------------------------------------

஢ ⥪  ࠡ⪨ 権  饩 窮
  㭪 15-1.   쬨 ᫮ ॣ஢ 
⥪  ࠧ 80 ⮢  ࠧ   ᮮ⢥⢥
७ ⢥ ⨯   i486.

᫮   ॣ  ⭮⥫쭮 ॣ
 設 ⥪.    ६  ॣ  設
⥪ 㪠  TOP (設 ⥪)  ᫮ ﭨ
 ࠡ⪨ 権  饩 窮. 樨 㧪
 ᥭ  ⥪ 㬥 TOP    㦠
祭   孨 ॣ.  ࠭ 
⠭  ⥪ ࠭ 祭  ⥪饣
TOP-ॣ,  ⥬ 㢥稢 TOP  .  ⥪
 , ॣ஢ ⥪  ࠡ⪨ 権  饩
窮    ࠢ  ॣࠬ  訬 ᮬ.

 ᫮   ࠧ ० 樨,
  ணࠬ    設 ⥪
  ஢ ।묨 ॣࠬ ⭮⥫쭮
設 ⥪ TOP. ᥬ ASM386/486 ন  ०
樨 ॣ஢, ᯮ ࠦ ST(0)   ST 
⮣, ⮡   ⥪饩 設 ⥪,  ST(i) 
⮣, ⮡ । i- ॣ  設 ⥪ TOP (0 <=
i <= 7). ਬ, ᫨ TOP ᮤন ᫮ 011B (ॣ 3 -
設 ⥪),  ᫥騩   ᮤন 
ॣ஢  ⥪ (ॣ 3  5):

FADD  ST, ST(2)

Ŀ
                                                               
                                                               
                      FPU                    
                                                       
                                                               
          79 78     64 63                              0  1  0 
     Ŀ  Ŀ 
  R0                                  
     Ĵ  Ĵ 
  R1                                                     
     Ĵ  Ĵ 
  R2                                                     
     Ĵ  Ĵ 
  R3                                                     
     Ĵ  Ĵ 
  R4                                                     
     Ĵ  Ĵ 
  R5                                                     
     Ĵ  Ĵ 
  R6                                                     
     Ĵ  Ĵ 
  R7                                                     
        
                                                               
     15                   0  47                              0 
     Ŀ  Ŀ 
                         
     Ĵ  Ĵ 
                            
     Ĵ   
                                                
                                         
                                                               


       㭮 15-1.  ஢ FPU  i486

࣠ ⥪   ⭮⥫쭮 設 ᫮
ॣ஢ ⥫쭮 頥 楤୮ ணࠬ஢, ⠪
  楤ࠬ । ࠬ १ ॣ஢
⥪.   ᯮ짮 ⥪  । ࠬ஢,  
ᯥ樠쭮 "饭" ⮬ ॣ஢, 뢠 楤
    ᯮ짮 ⥪.  ⥪ 
,  ணࠬ  㦠 ࠬ  ⥪ ।
⥬,  맢 - ணࠬ  ࠡ⪨ ᫥
⮢. ⥬ ணࠬ   ࠬ  ST,
ST(1)  ⠪ .  ⮬ TOP, ਬ,   뫠
 䨧᪨ ॣ 3   맮   䨧᪨ ॣ 5
 㣮.

15.1.2  ﭨ  ࠡ⪨ 権  饩
       窮
----------------------------------------------------------------

  㭪 15-2 16-ࠧ來 ᫮ ﭨ
ࠦ ᯥ樠쭮 ﭨ  ࠡ⪨ 権 
饩 窮.  ᫮ ﭨ   ࠭ 
    FSTSW/FNSTSW, FSTENV/FNSTENV  FSAVE
/FNSAVE,  ⠪ ।  ॣ AX    FSTSW AX
/FNSTSW AX,   ࠡ⪨ 楫᫥ 権
஢ ᫮ ﭨ  ࠡ⪨ 権  饩
窮.

 B ( 15) 祭  ᫮ ⮫쪮  ᮢ⨬ 
ᮯ஬ 8087.  ࠦ ᮤঠ  ES ( 7 ᫮
ﭨ).

   ᫮  ࠡ⪨ 権  饩
窮 (C3-C0)  䫠  :  i486 
   ⮣, ⮡ ࠧ १ 䬥᪨
権. ⢨     ᫮ ਢ 
 15-1.   ᫮  ਭ樯 ᯮ 
᫮ ⢫.  FSTSW AX ࠭ ᫮ ﭨ
 ।⢥  ॣ AX,   i486
ᬠਢ   ᫮.  SAHF  ஢
C3-C0 ।⢥   䫠  i486  ⮣,
⮡  ᫮ ⢫.   15- 2 
ᮮ⢥⢨  ⮢ ⠬ 䫠  i486.

       㭮 15-2.  ﭨ FPU  i486

Ŀ
                                                               
                                                               
                FPU       
                                                              
                     
               ĳ--        
                                                       
                                                       
             15               7             0                  
             Ŀ                 
             BC TOP CCCESPUOZDI                 
              3     210SFEEEEEE                 
                              
                                                       
                                                       
                              
                            
                                      
                            
                            
                          
                           
                         
                        
                                                               
   ES    ,      
    .    .   
                                                               
         2-1.     
    TOP:                                       
    000 =  0 -                              
    001 =  1 -                              
             .                                                 
             .                                                 
             .                                                 
    111 =  7 -                              
        3.             
                                                               
                                                               


 12-14 ᫮ ﭨ 㪠뢠  ॣ  ࠡ⪨
権  饩 窮,   ⥪饩 設
⥪ (TOP). 祭 設 ⥪ ᠭ  ।饬
ࠧ  ॣ஢ ⥪.

㭮 15-2   䫠 ᪫祭   0-5
᫮ ﭨ.  7 -   㬬୮ ﭨ
᪫祭 (ES).  ES ⠭, ᫨  ᪨㥬
 ᪫祭 ⠭,  饭  ⨢ 砥.  0
-5 㪠뢠  , 㦨   ࠡ⪨ 権 
饩 窮     ᫮ ᪫祭  
,   ﭨ 뫨 ᫥ ࠧ 饭 
⠭.  ""     饭 ⮫쪮
 FINIT, FCLEX, FLDENV, FSAVE  FRSTOR.

             15-1.   ᫮

Ŀ
                                                           
            C0       C3          C2           C1    
                                                           
Ĵ
                                                            
 FCOM, FCOMP,                                               
 FCOMPP, FTST,              ࠭          
 FUCOM, FUCOMP,      ࠢ         ࠢ      O/U# 
 FUCOMPP, FICOM,                                            
 FICOMP                                                     
Ĵ
 FXAM                        ࠭            
                                                    O/U#     
Ĵ
 FPREM, FPREM1                    0=᮪饭    Q1       
                   Q2       Q0    祭        O/U# 
                                  1= 祭           
Ĵ
 FIST, FBSTP,                                                
 FRNDINT, FST,                                               
 FSTP, FADD,                                                 
 FMUL, FDIV,                                        㣫 
 FDIVR, FSUB                             O/U# 
 FSUBR, FSCALE,                                              
 FSQRT, FPATAN,                                              
 F2XM1, FYL2X,                                               
 FYL2XP1                                                     
Ĵ
 FPTAN, FSIN,                      0=᮪饭    㣫 
 FCOS, FSINCOS         祭        O/U# 
                                   1= 祭 (᫨ C2=1
                                                  ।)
Ĵ
 FCHS, FABS,                                                 
 FXCH, FINCSTP,                                              
 FDECSTP, -                                            
  ⠭, FX-                            
 TRACT, FLD, FILD                                    O/U# 
 FBLD, FSTP (-                                            
 .⢥)                                            
Ĵ
 FLDENV, FRSTOR            㦥          
Ĵ
 FLDCW, FSTENV,                                               
 FSTCW, FSTSW,                                    
 FCLEX                                                        
Ĵ
 FINIT, FSAVE                              


O/U#          ᫨   IE  SF ⠭  ᫮
              ﭨ, 뢠 ᪫祭 ⥪,   
               祭 ९ ⥪ (C1=1) 
              ⥫쭮 ९ (C1=0).

饭    ᫨ १ 権 FPREM  FPREM1 ⮪,
                ⥫,  ᮪饭 祭.
              ᫨ ᮪饭  祭,   設 ⥪
              㤥 室  ⮪,  
              ᯮ짮  쭥襣 ᮪饭. 
               FPTAN, FSIN, FCOS  FSINCOS  ᮪饭
              ⠭  ⮬ 砥, ᫨ ࠭ 
              設 ⥪ ᫨誮 让.  ⮬ 砥
              室 ࠭ ⠥  設 ⥪.

㣫      ᫮ ﭨ ⠭  PE, 
              뢠, 뫮  ᫥ 㣫
              㣫 ᢥ.

     ᮤঠ । 祭.

 6  ⮬ 訡 ⥪ (SF).   ⫨砥
饭 , 騥  ᮡ ९ 
⥫쭮 ९ ⥪,  㣮 த 饭
.  SF ⠭,  9 (C1) । ९
⥪ (C1=1)  ⥫쭮 ९ ⥪ (C1=0).

     15-2. ⢥⢨  ⠬  FPU  IU

Ŀ
                                                              
           FPU                        IU             
                                                              
Ĵ
              C0                             CF               
                                                              
              C1                           ()            
                                                              
              C2                             PF               
                                                              
              C3                             ZF               



15.1.3 ࠢ饥 ᫮
----------------------------------------------------------------

 ࠡ⪨ 権  饩 窮 
ணࠬ⠬ ᯮ짮 ࠧ ० ࠡ⪨, 
롨 ।⢮ 㧪 ᫮    ࠢ饥
᫮.  㭪 15-3  ଠ  ஢  
ࠢ饬 ᫮.

訥  ⮣ ࠢ饣 ᫮ । ᪨஢
᫨⥫ ᪫祭.  0-5 ࠢ饣 ᫮ ᮤঠ
㠫 ᪨     ᫮ ᪫祭,
 ஬ i486,  ࠡ⪥ 権 
饩 窮. 訥  ࠢ饣 ᫮ ।
ࠬ ࠡ ன⢠ ࠡ⪨ 権  饩
窮, 騥  ᥡ:

- ࠢ 筮

- ࠢ 㣫

 ࠢ 筮 ( 8-9)   ᯮ짮 
⮣, ⮡ ⠭  筮 ७ 権
ன⢠, 祬 筮  㬮砭 (  64- ).
  ࠢ   ᯮ짮  ।⠢
ᮢ⨬  ࠭ ﬨ 䬥᪨ ஢,
   筮, 祬  i486 
䬥᪨ ᮯ 387.  ࠢ 筮
 ⮫쪮  १ ᫥ 䬥᪨
権: ADD, SUB(R), MUL, DIV(R)  SQRT.  㣨
樨  ࠢ 筮.

 ࠢ 㣫 ( 8-9) ।⠢ 
० 㣫  襣,  ⠪ ।⢥
㣫  ⨭ 祭. ࠢ 㣫
 ⮫쪮  䬥᪨ 樨 (ᯨ᮪
䬥᪨  䬥᪨ 権 ਢ   16).

15.1.4  ⥣ ன⢠ ࠡ⪨ 権  饩
       窮
----------------------------------------------------------------

 ⥣ 㪠뢠 ᮤঠ  ॣ 
ॣ஢ ⥪,    㭪 15-4.  ⥣
ᯮ ᠬ 㫥 ࠡ⪨ 権  饩 窮
 ⮣, ⮡ ⫨ ⮥  ⮥  ॣ஢.
 ணࠬ஢ ࠡ稪 ᪫祭  ᯮ짮
 ଠ  ⮣, ⮡ ஢ ᮤন ᫮
ॣ஢  믮 ᫮ ᪮஢ 
  ॣ. 祭 ⥣  ᫮ ⥣ ᮮ⢥
䨧᪨ ॣࠬ 0-7. ணࠬ  ᯮ짮
㪠⥫  ⥪ 設 ⥪ (TOP), ࠭  ᫮
ﭨ ,  ⮣, ⮡ ᮯ⠢  祭 ⥣
 ⭮⥫묨 ॣࠬ ⥪  ST(0)  ST(7).

Ŀ
                                                               
                                                               
                  
                  ( )*  
                      
                        
                                                       
                                                       
             15               7             0                  
             Ŀ                 
             X X  XR CP CX XPUOZDI                 
                            MMMMMM                 
                              
                                                       
                                                       
                           
                                          
                            
                            
                          
                           
                         
                        
                                                               
                                          
    00 -                     
    01 -    (  )      
    10 -    (  )          
    11 -  ( )                     
                                                               
                                            
    00 - 24  ( )                            
    01 - ()                                     
    10 - 53  ( )                            
    11 - 64  ( )                        
                                                               
  * -   "ࠢ ᪮筮"  ⠭  
        i486(TM).  প ᮢ⨬    
      ஬ 80287     ணࠬ஢;  
      , ᨬ   祭, FPU        
      i486(TM) ࠪ ᪮筮  䨭 ᫥         
      (    ᪮筮).                        
                                                               
                                                               


  㭮 15-3. ଠ ࠢ饣  FPU  i486

 祭 ⥣    믮
 FSTENV  FSAVE,  ᮮ⢥⢨  ⢨⥫
ᮤঠ   ⥪.   믮
㣨 ,  i486  ᫮ ⥣ ⮫쪮 
⮣, ⮡ 㪠,    ⥪  
.

Ŀ
                                                               
   15                                                      0   
   Ŀ   
   - - - - - - - -    
   (7)(6)(5)(4)(3)(2)(1)(0)   
      
                                                               
    :                                          
      00 =                                           
      01 =                                                 
      10 = :  (NaN, ),       
                                  
      11 =                                                
                                                               
                                                               


              㭮 15-4. ଠ  ਧ


15.1.5 ⥫ ᫮   
----------------------------------------------------------------

⥫     ࠡ  ணࠬ㥬묨
ࠡ稪 ᪫祭.  ॣ 㯭 १
ESC- FLDENV, FSTENV, FSAVE  FRSTOR. ᥣ, 
 i486 ᪮ ESC-,  ࠭ 
,  ࠭ (᫨ )   樨.

 ࠭  , 㪠⥫    室
    ଠ⮢,  ᨬ  ० ࠡ
 (饭 ०  ० ᮫⭮ 樨)  
ᨬ  ਡ ࠧ ࠭ (32  16 ⮢
࠭).  ० 㠫쭮  8086 ᯮ
ଠ ० ᮫⭮ 樨.

    㭪 15-5  㭪 15-8 
㪠⥫  ⠪,   ࠭ ᫥ 
FSTENV.

Ŀ
                                                               
             32-                 
                                                               
     31           23          15          7          0         
     Ŀ         
                     0H      
     ĳĴ         
                       4H      
     ĳĴ         
                        8H      
     ĳĴ         
              IP (㪠⥫ )          CH      
     ĳĴ         
                    CS       10H     
     ĳĴ         
                               14H     
     ĳĴ         
                     18H     
              
                                                               
                                                               


㭮 15-5. ᫮  饭   ⮡ࠦ
              ⥫   , 32-  ଠ

Ŀ
                                                               
         32-             
                                                               
  31           23          15          7                0      
  Ŀ      
                        0H   
  ĳĴ      
                          4H   
  ĳĴ      
                           8H   
  ĳĴ      
                 15..0  CH   
  Ĵ      
  0000      31..160  10.0 10H  
  ĳĴ      
               15..0   14H  
  ĳĴ      
  0000   31..16      000000000000    18H  
        
                                                               
                                                               


㭮 15-6. ᫮   ᮫⭮ 樨 
              ⮡ࠦ ⥫   , 32-ࠧ來
              ଠ

Ŀ
                                                               
             16-                 
                                                               
            15               7              0                  
            Ŀ                  
                            0H               
            Ĵ                  
                              2H               
            Ĵ                  
                               4H               
            Ĵ                  
              IP(㪠⥫ ) 6H               
            Ĵ                  
                        CS          8H               
            Ĵ                  
                            AH               
            Ĵ                  
                            CH               
                              
                                                               
                                                               


㭮 15-7. ᫮  饭   ⮡ࠦ
              ⥫   , 16- ⮢ ଠ


 FSTENV  FSAVE ࠭    , 
ࠡ稪 ᪫祭 । ⨤  ᪫祭,
஥  .

  㪠뢠   䨪,  ।
,    ⥬᪨ ᮯ 387  80287.
  ⫨稥  ᮯ 8087,  ண 
 㪠뢠 ⮫쪮   ESC-.

Ŀ
                                                               
         16-             
             8086           
                                                               
            15               7              0                  
            Ŀ                  
                            0H               
            Ĵ                  
                              2H               
            Ĵ                  
                               4H               
            Ĵ                  
                    15..0   6H               
            Ĵ                  
                                                  
                0  10..0 8H               
             19..16                                        
            Ĵ                  
                  15..0    AH               
            Ĵ                  
                                                  
                0   00000000000     CH               
             19..16                                        
                              
                                                               
                                                               


㭮 15-8. ᫮   ᮫⭮ 樨 
              ⮡ࠦ ⥫   , 16-⮢
              ଠ


 ,   ࠢ ஬ FINIT,
FLDCW, FSTCW, FSTSW, FCLEX, FSTENV, FLDENV, FSAVE  FRSTOR 
  㪠⥫ .  ⠪   ,
 祭 㪠⥫  ।, ᫨ । ESC-
   ࠭ . ⢥ ᪫祭
⠢ ⮫쪮  㯮 .

15.2 ᭮ ᫥
----------------------------------------------------------------

 ࠧ 뢠 楯樨 ᫨⥫쭮
ணࠬ஢,   騬   ਪ
⥬.  ⮬ ࠧ 뢠 ஥ ⥬ ᥫ,
ਭ  㫥 ࠡ⪨ 権  饩 窮
 i486,  ⠪ ࠧ ⨯ ᥫ,  
⢮  ᫨⥫ ணࠬ.  ᠭ
  ᯮ㥬 ਠ 㣫  筮
(⠭ ﬨ  ࠢ饬 ᫮)   筥
  ᯮ㥬 ⥩, ⠢ 
᫥ ࠧ. ᫮ ᪫祭,   
  믮   饩 窮, ਢ 
 ਠ   ﬨ,  ॠ  
᪫祭.

15.2.1 ⥬ ᥫ
----------------------------------------------------------------

⥬ ⢥ ᥫ,   ᯮ㥬  
᫥, ᪮筠   ஭.   孥 
 ࠭  ᥫ,    ᯮ짮 
,   筮 (⢠  ), 
 ॡ  ।⠢  ᥫ.  
 ⢥ ᫠ ᥣ  ᪮筮
⢮ ᥫ,     ⮣ ᫠. ஬
⮣,  ᪮筮  ᥫ  
⢥묨 ᫠. ਬ,  ᫠ 2.5  2.6
 ᫠ 2.51, 2.5897, 2.500001  ⠪ .

   ⥫쭮 뫮  筮, ⮡ 
㫨஢  ᥬ ⢥ ⢥ ᥫ,  
ࠪ⨪  . ,  ᨬ  
稭,  ࠭祭 ࠧ ॣ஢  ,
, ᮡ⢥,  ࠭稢 ⥬ ᥫ, ॠ㥬
 .  ࠭祭 ।  , ⠪ 
筮 ᥫ.  १ 砥 ⢮ ᥫ, ஥
 ࠭祭  ,   ᪮ 
࠭祭.  ᫥⥫쭮 ।⠢ ᮡ
⢮ ⢨⥫ ᥫ  ࠧࠡ⠭  ⮣, ⮡
ନ஢  பᨬ ⥬ ⢥ ᥫ,
  뫮  ᯮ짮  .

 㭪 15-9   ⥬ ᥫ  饩
窮  i486  ⢥ אַ ( ᭮
  ᫠,  ᠬ   i486
ᯮ ᫠  筮 ।⠢). 窨 㪠뢠
⢮ ⢨⥫ ᥫ, ஥  i486 
।⠢      १ ᫥.
ଠ ᫠   筮   ਬ୮
  +-2.23 x 10**(-308)  +-1.79 x 10**(308).  ⮬
祭 ।   砨,  ணࠬ
ᯥ祭 ॡ ࠡ  묨   १⮬ 
ࠬ ⮣ .  ࠢ ਢ  ᥫ
 IBM System 370*,  ⠢ ਬ୮  +-0.54 x
10 **(-78)  +-0.72 x 10**(76).

Ŀ
                                                               
                                                               
                                                               
                                     
  |       |   |       |  
  |     ()    |   |     ()    |  
  |      -5  -4  -3  -2  -1  |   |  1 2Ŀ 3   4   5       |  
  *) (***************** 0 ***************) (*  
                                   Ŀ               
           308         -308           -308          308   
   -1.79x10     -2.23x10      2.23x10      1.79x10    
                                                              
                                                              
                            Ŀ    
                                     +2                      
                               ***                 
                                                           
                                                       
                                    2.000000000000000     
                                    ( )     
                                  1.999999999999999      
                              16       
                                                             
                                
                                                               
                                                               
                                                               


          㭮 15-9. ⥬ ᥫ  筮

࠭祭 ࠭⢮  㭪 15-9  , 
 i486  ।⠢ 쭮  ⢥
ᥫ,   ,  ⮣ . ᥣ 
࠭⢮   ᥤ ᫠  饩 窮 
,  १ ᫥    ࠭⢮.
 ⠪ 砥,  ࠡ⪨   饩
窮 㣫 ⨭ १  ᫠, ஥  
।⠢. ⢥ ᫮, ஥ ॡ  ,
祬  ࠡ⪨ 権  饩 窮   (
 ᫮  20- ), ।⠢  ன ३
筮.   ⠪  ,  ।⠢ ᫠
ᯮ  ஢  ⢥ אַ. ᪨
⠪  ⢮ ।⠢ ᥫ   묨
 ᫥⥫묨 ⥯ﬨ  (  ⠪ 
⢮ ।⠢ ᥫ    2  4, ⠪ 
 65536  131072). , ﭨ  ।⠢묨
᫠   ᥫ, 稭  . , 
楫   +-2**(64) (ਬ୮ +-10**(19)) ।⠢
筮.

 ७   ࠡ⪨ 権  饩
窮  ᠬ  ࠡ⠥  ⥬ ᥫ,  
⢥ ⢮ ⥬,   㭪 15-9.
७ ଠ (뢠 ७ ⢥)
 ଠ  ।⠢ ᥫ ਬ୮
 +-3.37 x 10**(-4932)  +- 1.18 x 10**(4932),  筮
ਬ୮  19 ( 筮 ) .  ଠ ࠧࠡ⠭
 ⮣, ⮡ ।⠢ ⥫   筮
 ⠭  ஬ १⮢,   ਬ  
 筮 १.

 ࠪ᪮ 窨 ७, ⢮ ⢨⥫ ᥫ
 i486 筮   ⭮  ⮣, ⮡ 
࠭稢  設⢠ ਪ ணࠬ. 
ࠢ  設⢮ ஢,  訥 設,
 i486  祭  பᨬ ⥬
⢥ ᥫ.  ⮬, ,  ,   
筮 ।⠢   ୠ 䬥⨪ 
⢥묨 ᫠    ਡ.

15.2.2   ଠ 
----------------------------------------------------------------

 i486 ࠧ砥 ᥬ ⨯ ᫮   .
 ࠧ   :  楫, 㯠
 楫   ⢥.  ᫥ ࠧ
㤥  ଠ  ⮬,    ଠ ࠭ 
 ( ᥣ ᯮ  ᠬ 孥 ).

 㭪 15-10 ਢ ଠ  ⨯  
設⢮    ᥫ (   ᥫ)
 ஭ ࠬ.

15.2.2.1  楫
----------------------------------------------------------------

 ଠ  楫 ⮦⢫ ᢮ , 
ࠢ , ।⠢   ଠ.  
 ࠪ   ᫠: 0=⥫쭮, 1=⥫쭮.
⥫ ᫠ ।⠢  ⠭⭮ 樨
  筮 ⥬ ᫥ ( 楫 
 ⮫쪮  ଠ  i486  ⮣, ⮡  뫮
ᯮ짮   筮 ⥬ ᫥). ᫮
 ।⠢  ⥫  (  㫨).
ଠ 楫 ᫮   i486 ⮦⢫ 
16-ࠧ來 楫᫥ ⨯   ; ଠ
⪮ 楫 ⮦⢫  32-ࠧ來 楫᫥
⨯   .

   楫᫥ ଠ  ⮫쪮 
.  ᯮ짮 㫥 ࠡ⪨ 権  饩
窮  i486  ⮬᪨ ॢ  80-
 ७ ⢥ ଠ.   楫
 筮 ।⠢묨  ७ ⢥ ଠ.


Ŀ
                                                
   -               
       Ĵ
                     7 07 07 07 07 07 07 07 07 07 0
Ĵ
       4        Ŀ (   
     10  16    )                   
                     15     0                               
Ĵ
    9        Ŀ (  
     10  32    )   
                     31             0                       
Ĵ
     18       Ŀ(-
     10  64   
                     63                             0  2)
Ĵ
                     Ĵ
-   18       S  X d  d  d        d  d  d  d 
 BCD   10  18      17 16 15  * * * * * * 3  2  1  0
                     Ĵ
                     79                                    0
Ĵ
                     Ŀ                    
                     S.                    
    -38                                    
  10  24                     
                     31       23       0                    
Ĵ
                     Ŀ       
                                                
   -308       S                    
 10   53        
                     63           32                0       
Ĵ
                     Ĵ
--4932       S      Ŀ           
 - 10   64                             
                Ĵ
                     79             64 63                 0
Ĵ
                                                               
 (1) S =   (0 = ⥫, 1 = ⥫)      
 (2) d =   (  )                         
      n                                                        
 (3) X = ,   ;  
                   
 (4)  =                            
 (5)  =   ;      
         ,        - 
                                                          
 (6)   ( )              
     : 127 (7FH)                                        
     : 1023 (3FFH)                                      
      : 16383 (3FFFH)                   
                          s                                    
 (7)  BCD: (-1) (D  ...D )                          
                             17    0                           
                       s  E BIAS                               
 (8) : (-1) (2      ) (F F ...)                    
                                    0 1                        
                                                               
                                                               


             㭮 15-10. ଠ ᫮ 


15.2.2.2  楫
----------------------------------------------------------------

 楫 ࠭  㯠 筮 樨 
 묨 ࠬ, 㯠묨   .
᪫祭 ⠢ ⮫쪮 ᠬ  ,  ᮤন
  (0=⥫쭮, 1=⥫쭮). ⥫
᫠  ࠭  ଥ   筮 ⥬
᫥  ⫨  ⥫ ᥫ ⮫쪮 ⮬
. 騥  稭 ᫥.     
 0-9.

ଠ  楫  ⮫쪮  . 
ᯮ짮 㫥 ࠡ⪨ 権  饩 窮
 i486,  ⮬᪨ ॢ  80-ࠧ來
७ ⢥ ଠ.   楫 
筮 ।⠢묨  ७ ⢥ ଠ.

15.2.2.3 ⢥ ᫠
----------------------------------------------------------------

 i486  ।⠢ ⢥ ᫠ :

(-1)**(s)2**(E)(b(0)b(1)b(2)b(3)...b(p-1))

:

s     = 0  1
E     =  楫  Emin  Emax, ⥫쭮
b(i)  = 0  1
p     = ᫮  筮

  15-3 ਢ ࠬ    ଠ⮢
⢥ ᥫ.

 i486 ࠭ ⢥ ᫠  筮 ଠ 
६ ﬨ,  ࠦ   ᯮ樠
. ଠ ⮨  ᫥ :

- 騥  ᫠ 室   
  b(0)b(1)b(2)b(3)...b(p-1).

-  浪, e = E + ᬥ饭 冷, ᯮ 
      ( । 稭 ᫠).

- ⮢   㪠뢠  ,   ᫮
  ⥫  ⥫. ⥫ ᫠
  ⫨  ⥫ ⮫쪮    ᢮
  .

                 15-3. ࠬ ଠ⮢

Ŀ
                                       ଠ                 
        ࠬ        Ĵ
                                  ७ 
Ĵ
 ਭ ଠ        32            64         80    
 p ( 筮)           24            53         64    
 ਭ 浪         8            11         15    
 Emax                      +127         +1023     +16383    
 Emin                      -126         -1022     -16382    
 饭 冷         +127         +1023     +16383    


  15-4   ⢥ ᫮ 178.125
(筮) ࠭  筮 ⢥ ଠ. 
⠡ ਢ ண  権, 
ࠦ   ⮦ 祭  ⮣, ⮡   ᫮
  ॢ   ଠ  㣮. (࠭ 
몠 ᥬ ASM386/486  PL/M-386/486 ந 
樨,    ⢥ ᫮ ⠭,
। ணࠬ⮬.)    ,   
筨 ஡    . 筮
᫮ 1/10, ਬ,    筮 ࠦ  筮
ଠ (⠪  ᫮ 1/3    筮 ࠦ 
筮 ଠ).  ࠭ 砥 ⠪ 祭,
  பᨬ 㣫 筮 ᫠ 
筮 祭.

 i486 筮 ࠭    ଠ
ଥ.  砥,  , ᪫ 㫥 祭,
ᮤন 楫   ஡ :

1fff...ff

  砥 ।  . ᫮ ஡
⮢   ᮮ⢥⢨  ⢥ ଠ⮬: 23 
⮣, 52    63  ७ ⢥.
ଠ ⢥ ᫠ ⠪, ⮡   楫 
ᥣ  ࠢ 1,  i486 㭨⮦ 砫 㫨 
 祭 (X < 1).  ਥ ᨬ ᫮
 ,    ।⠢   
ਭ.  ,   ⮬   ଠ
 楫      ⢨⥫쭮 
࠭;  楫  䨧᪨ ।⠢ ⮫쪮 
७ ଠ.

᫨ ᬮ ⮫쪮    । 筮
窮,   ଠ ⢥ ᫠  
祭 訥 祬  ࠢ 1  訥 祬 2. 
     ᯮ  浪. 
  筮 筮 樨, ⥫ 冷 ᤢ
  ࠢ,  ⥫쭩 冷 ᤢ 
 , ⠢ 砫 㫨  室.
ᬥ饭 冷  㪠뢠,   ।
筮 窨  ⠪  樥 ॠ쭮 筮
窨. ⥬  浪 । 稭 ⢥
᫠.

            15-4.  ⢥ ᫠

Ŀ
                                                              
                         祭                      
                                                              
Ĵ
   筠                                                    
  筠      178.125                                     
Ĵ
   筠                                                    
  筠      178125E2                                   
Ĵ
   筠                                                    
  筠        10110010001E111                            
Ĵ
   筠                                                    
  筠        10110010001E10000110                       
(.冷)                                                
Ĵ
       饭 冷                 
   ଠ     Ĵ
(ଠ) 0      10000110      01100100010000000000000 
                                           1 ()      


 ⮣, ⮡  ࠢ ⢥ ᥫ
(ਬ,  ஢),  i486 ࠭ 浪 
ᬥ饭 ଥ.  砥,  ⠭  
⨭ 浪, ᠭ .     15-3,
祭 ᬥ饭 ࠧ筮   ⢥ ଠ.
 ࠭ ⠪, ⮡ 㤨 ᬥ饭 冷 
⥫쭮 祭.   ࠢ 
⢥ ᫠ ( ଠ  ) ⠪,  ᫨
  뫨 묨 楫묨  .  ࠧ, 
⭮ ࠢ ᥫ ᫥ ࠢ (稭  ᠬ 
 浪),   ⫨  । ⭮襭 
ᥫ, ⮬  室  ࠢ .
⨭ 冷 ᫠   ।  ⠭
祭 ᬥ饭  ଠ.

⮩   ⢥ ଠ  ⮫쪮 
. ᫨ ᫮, ।⠢     ଠ⮢,
㦠  ॣ  ࠡ⪨ 権  饩
窮,   ⮬᪨ ॢ  ७ ଠ,
 ᯮ   ७ 権.  
ࠧ   ॣ   ॢ  ⮩ 
 ⢥ ଠ  ࠭  . ७
⢥ ଠ   ᯮ짮 ⠪   ,
筮  ࠭ ஬ १⮢,  
  ॣ.

設⢮ ணࠬ த⮢  ᯮ짮 
ଠ  ࠭ ᫮ ⢥   १⮢.
 ।⠢    筮  祭
४ १⮢  묨 ⠬  ஭
ணࠬ. ⮩ ⢥ ଠ 室 
ணࠬ த⮢,  ᭥ ,  ᫥
,   ଠ    .  ⠪
ᯮ  ⫠ ⬮, ᪮ ஡
㣫   ॥  ⮬ ଠ. ७
⢥ ଠ 筮 ᯮ  ࠭
஬ १⮢, 稪 横  ⠭. 
ଠ     ⮣, ⮡ ࠤ 
१  ⢨ 㣫  ९/⥫쭮
९  ஬ ᫥.  ⮬  
筮  ଠ ⭠ 設
ப ॠ権.

15.2.3 ࠢ 㣫
----------------------------------------------------------------

 ७ ।⠢  ࠡ⪨ 権 
饩 窮  i486 ᯮ  ⥫
 ( ,  㣫   ), 
ਬ  㣫 ᥫ  ᮮ⢥⢨  ⨭
१⮬ ᪮筮 筮 ᫥.   
㯭  ணࠬ. ᥣ,   
।⠢ ⨭ १ ᪮筮 筮, 
ࠡ⪨ 権  饩 窮   ந
㣫. 㣫 ந  䬥᪨  
 ࠭,  ଠ    筮
।⠢ ⨭ १  ᪮筮 筮.
ਬ, ⢥ ᫮   㣫, ᫨ 
࠭   ⪮ ⢥ ଠ  
楫᫥ ଠ. ⨭ १ ᪮筮 筮
⠪   㣫  ᥭ  ॣ.

 ࠡ⪨ 権  饩 窮  i486
  ० 㣫, ⠭  
ࠢ 㣫 (RC) ࠢ饣 ᫮ (ᬮ 㭮
15-3).   ⨭ १ b,    
।⠢ 㦭 ⨯ ,  ࠡ⪨ 権 
饩 窮 ।  ।⠢ ᫠ a  c,
  筮 室  祭 ᫠ b   ஭
(a < b < c). ⥬  㣫 () b  a  c 
ᮮ⢥⢨  ०, ⠭   㣫, 
   15-5. 㣫   १ 訡,
   祬   ࠧ拉,  ஬ 
㣫.

                 15-5.  㣫

Ŀ
 ࠢ-                                             
   㣫        ⢨  㣫       
                                                      
Ĵ
    00     㣫   ।塞,  祬  b:  a 
           襣     c; ᫨ ᫮ ࠢ㤠   
                          ᥫ,  롮 ⭮ ᫠ (, 
                           ண 訩 騩  
                          㫥).                          
Ĵ
    01       㣫                                      
               ᭨           a                             
              ( -x)                                        
Ĵ
    10       㣫                                      
               ᢥ          c                             
              ( +x)                                        
Ĵ
    11       祭    襥  a  c              
              ( 0)                                         


 : a < b < c; a  c - ᯥ譮 ।⠢ ᫠;
                   b -  ।⠢.

- "㣫  襣" -  ० ⠭ 
  㬮砭  ਬ   ணࠬ த⠬; 
  ।⠢  筮  ᪨ ᬥ饭
  業 ⨭ १.

-  "祭"  "㣫  " ਬ 
  楫᫥ 䬥᪨ .

- "㣫   ஭"  "㣫  
  ஭" 뢠 ਥ஢ 㣫   
  ᯮ짮  ॠ樨 ࢠ쭮 䬥⨪.
  ࢠ쭠 䬥⨪ ᯮ  । 孥 
   ࠭  ⨭ १ 㯥
  ⮢  㣫 ஬ १⮢ ᫥.

ࠢ 㣫 ਬ ⮫쪮  䬥᪨
 (ᯨ᮪ 䬥᪨  䬥᪨ 
ਢ   16).

15.2.4 ࠢ 筮
----------------------------------------------------------------

 ࠡ⪨ 権  饩 窮  i486
  १  筮 64, 53  24  
,  ⠭   ࠫ 筮
(PC) ࠢ饣 ᫮. 砫쭮 ⠭ 筮, 
 ᠬ ᯮ㥬  ணࠬ த - 筮 64-
  , ।⠢塞 ७ ⢥
ଠ⮬. 㣨 ० 筮  易⥫묨 
ᮮ⢥⢨  ⠭⮬ IEEE  ।⠢ 
ᮢ⨬  ᯥ䨪ﬨ  
⬨᪨ 몮. 롮 襩 筮  
ᯮ짮 २⢠  ஡ ७ ଠ.
 롮 襩 筮, 㣫 ஡ 祭
 ᯮ㥬  ࠢ. ࠢ 筮
ਬ ⮫쪮   FADD, FSUB, FMUL, FDIV  FSQRT.

