Intel 8087
The first floating-point coprocessor in the x86 ecosystem, introduced by Intel. It uses an 80-bit extended-precision internal format, supports the IEEE 754 standard, and implements operations such as floating-point addition and subtraction through microcode control.
Timeline (last 90 days)
The 15-bit exponent of the 8087's 80-bit extended precision format uses a biased representation with an offset of 16383, covering a dynamic range of approximately 10 to the power of -4932 to 10 to the power of +4932.
The 8087 performs addition and subtraction internally in extended precision, rounding to single or double precision only when writing back to memory.
The 8087 supports four rounding modes: round to nearest, round toward zero, round toward positive infinity, and round toward negative infinity.
The 8087 uses the status word to record exception flags and the control word to determine whether to trigger interrupts.
The 8087 contributed the gradual underflow mechanism during the formulation of IEEE 754, namely outputting denormalized numbers rather than simply flushing to zero.
The 8087's addition and subtraction are driven by microcode sequences in the chip's internal ROM and are not a fully hardwired design.
The 8087 uses a stack-based register structure, with eight 80-bit registers forming a circular stack.
The 8087's subtraction shares the data path with addition through negate-and-add-one, rather than using separate circuitry.
When the exponent difference exceeds a certain threshold, the 8087 short-circuits the small operand to exit the logic early and save cycles.
All Facts (9)
The 15-bit exponent of the 8087's 80-bit extended precision format uses a biased representation with an offset of 16383, covering a dynamic range of approximately 10 to the power of -4932 to 10 to the power of +4932.
50%UnverifiedThe 8087 performs addition and subtraction internally in extended precision, rounding to single or double precision only when writing back to memory.
50%UnverifiedThe 8087 supports four rounding modes: round to nearest, round toward zero, round toward positive infinity, and round toward negative infinity.
50%UnverifiedThe 8087 uses the status word to record exception flags and the control word to determine whether to trigger interrupts.
50%UnverifiedThe 8087 contributed the gradual underflow mechanism during the formulation of IEEE 754, namely outputting denormalized numbers rather than simply flushing to zero.
50%UnverifiedThe 8087's addition and subtraction are driven by microcode sequences in the chip's internal ROM and are not a fully hardwired design.
50%UnverifiedThe 8087 uses a stack-based register structure, with eight 80-bit registers forming a circular stack.
50%UnverifiedThe 8087's subtraction shares the data path with addition through negate-and-add-one, rather than using separate circuitry.
50%UnverifiedWhen the exponent difference exceeds a certain threshold, the 8087 short-circuits the small operand to exit the logic early and save cycles.
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