  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. 
