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This HTML version of the file intel.doc from the
PC Game Programmer's guide was produced by Zack T Smith. Fancy HTML modifications are copyright ©
2005 by Zack T Smith, all rights reserved.
This information is provided in the hope that it will be useful,
but without any warranty. It is provided AS-IS,
without even the implied warranty of fitness for a particular purpose.
B Instructions
BOUND - Array Index Bound Check (80188+)
Usage: BOUND src,limit
Modifies flags: None
Array index in source register is checked against upper and lower
bounds in memory source. The first word located at "limit" is
the lower boundary and the word at "limit+2" is the upper array bound.
Interrupt 5 occurs if the source value is less than or higher than
the source.
Clocks Size
Operands 808x 286 386 486 Bytes
reg16,mem32 - nj=13 nj=10 7 2
reg32,mem64 - nj=13 nj=10 7 2
- nj = no jump taken
BSF - Bit Scan Forward (386+)
Usage: BSF dest,src
Modifies flags: ZF
Scans source operand for first bit set. Sets ZF if a bit is found
set and loads the destination with an index to first set bit. Clears
ZF is no bits are found set. BSF scans forward across bit pattern
(0-n) while BSR scans in reverse (n-0).
Clocks Size
Operands 808x 286 386 486 Bytes
reg,reg - - 10+3n 6-42 3
reg,mem - - 10+3n 7-43 3-7
reg32,reg32 - - 10+3n 6-42 3-7
reg32,mem32 - - 10+3n 7-43 3-7
BSR - Bit Scan Reverse (386+)
Usage: BSR dest,src
Modifies flags: ZF
Scans source operand for first bit set. Sets ZF if a bit is found
set and loads the destination with an index to first set bit. Clears
ZF is no bits are found set. BSF scans forward across bit pattern
(0-n) while BSR scans in reverse (n-0).
Clocks Size
Operands 808x 286 386 486 Bytes
reg,reg - - 10+3n 6-103 3
reg,mem - - 10+3n 7-104 3-7
reg32,reg32 - - 10+3n 6-103 3-7
reg32,mem32 - - 10+3n 7-104 3-7
BSWAP - Byte Swap (486+)
Usage: BSWAP reg32
Modifies flags: none
Changes the byte order of a 32 bit register from big endian to
little endian or vice versa. Result left in destination register
is undefined if the operand is a 16 bit register.
Clocks Size
Operands 808x 286 386 486 Bytes
reg32 - - - 1 2
BT - Bit Test (386+)
Usage: BT dest,src
Modifies flags: CF
The destination bit indexed by the source value is copied into the
Carry Flag.
Clocks Size
Operands 808x 286 386 486 Bytes
reg16,immed8 - - 3 3 4-8
mem16,immed8 - - 6 6 4-8
reg16,reg16 - - 3 3 3-7
mem16,reg16 - - 12 12 3-7
BTC - Bit Test with Compliment (386+)
Usage: BTC dest,src
Modifies flags: CF
The destination bit indexed by the source value is copied into the
Carry Flag after being complimented (inverted).
Clocks Size
Operands 808x 286 386 486 Bytes
reg16,immed8 - - 6 6 4-8
mem16,immed8 - - 8 8 4-8
reg16,reg16 - - 6 6 3-7
mem16,reg16 - - 13 13 3-7
BTR - Bit Test with Reset (386+)
Usage: BTR dest,src
Modifies flags: CF
The destination bit indexed by the source value is copied into the
Carry Flag and then cleared in the destination.
Clocks Size
Operands 808x 286 386 486 Bytes
reg16,immed8 - - 6 6 4-8
mem16,immed8 - - 8 8 4-8
reg16,reg16 - - 6 6 3-7
mem16,reg16 - - 13 13 3-7
BTS - Bit Test and Set (386+)
Usage: BTS dest,src
Modifies flags: CF
The destination bit indexed by the source value is copied into the
Carry Flag and then set in the destination.
Clocks Size
Operands 808x 286 386 486 Bytes
reg16,immed8 - - 6 6 4-8
mem16,immed8 - - 8 8 4-8
reg16,reg16 - - 6 6 3-7
mem16,reg16 - - 13 13 3-7
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