André Pouliot wrote:
If we want to save resource we could expect all value to be normalized
even number that should be unnormalized. We could also expect when the
exponent is zero the value to always be zero it would diminish the
dynamic range but simplify a lot of the code and make corner case easier
to handle. Or we could stick to the spec of IEEE and augment the logic
to do so, it would take at least 1 or 2 more stage and at least 280 more
LUT(big mux for selecting the value to output as mantissa, doing the
same function in asic it would be a barrel shifter, custom made it would
be rather small and fast).
Remember that this is an FPU to implement a 2D/3D pipeline,
not a full maths coprocessor. Just throw away all the
complex edge cases in IEEE floating point and adopt the
following rules: all little numbers == 0, all really big
numbers == infinity.
Graphic programmers want speed, speed, and more speed, and
we *don't* want the graphics card grinding to a halt and
reporting exceptions. (Those programmers who do have a need
for precise calculations will use double precision on the
CPU anyway.)
--
Hugh Fisher
DCS, ANU
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