FSCALE
Usage: FSCALE dest,src Modifies flags: See below.
Truncates the value in the 'src' operand (toward 0) to an integral value and adds that value to the exponent of the 'dest' operand. The 'dest' and 'src' operands are floating-point values located in registers ST(0) and ST(1), respectively. This instruction provides rapid multiplication or division by integral powers of 2.
Scale Floating-Point Value by Power of Two
FSCALE ; D9 FD [8086,FPU]
FSCALE scales a number by a power of two: it rounds ST1 towards zero to obtain an integer, then multiplies ST0 by two to the power of that integer, and stores the result in ST0.
FPU Flags Affected C1 Set to 0 if stack underflow occurred. Set if result was rounded up; cleared otherwise. C0, C2, C3 Undefined.
Example:
fscale