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E-29
INSTRUCTION SET SUMMARY
Table E-9. Encoding of 32-bit Address Mode (“mod r/m” Byte and s-i-b Byte Present)
mod r/m Effective Address
00 000
00 001
00 010
00 011
00 100
00 101
00 110
00 111
01 000
01 001
01 010
01 011
01 100
01 101
01 110
01 111
10 000
10 001
10 010
10 011
10 100
10 101
10 110
10 111
DS:[EAX + (scaled index)]
DS:[ECX + (scaled index)]
DS:[EDX + (scaled index)]
DS:[EBX + (scaled index)]
SS:[ESP + (scaled index)]
DS:[d32 + (scaled index)]
DS:[ESI + (scaled index)]
DS:[EDI + (scaled index)]
DS:[EAX + (scaled index) + d8]
DS:[ECX + (scaled index) + d8]
DS:[EDX + (scaled index) + d8]
DS:[EBX + (scaled index) + d8]
SS:[ESP + (scaled index) + d8]
SS:[EBP + (scaled index) + d8]
DS:[ESI + (scaled index) + d8]
DS:[EDI + (scaled index) + d8]
DS:[EAX + (scaled index) + d32]
DS:[ECX + (scaled index) + d32]
DS:[EDX + (scaled index) + d32]
DS:[EBX + (scaled index) + d32]
SS:[ESP + (scaled index) + d32]
SS:[EBP + (scaled index) + d32]
DS:[ESI + (scaled index) + d32]
DS:[EDI + (scaled index) + d32]
NOTE: Mod field in “mod r/m” byte; ss, index, base fields in “s-i-b” byte.
ss Scale Factor
00
01
10
11
x1
x2
x4
x8
Index Index Register
000
001
010
011
100
101
110
111
EAX
ECX
EDX
EBX
no index reg†
EBP
ESI
EDI
†
When index field is 100, indicating “no index register,”
the ss field must equal 00. If this is not true, the
effective address is undefined