(j3.2006) decimal floats
Sun Jan 13 11:49:58 EST 2008
On Sat, 12 Jan 2008, Craig Dedo wrote:
> Well, the most widely used chip of all, the Intel 80x87 and its
> successors, has two different radices. It has both binary floating point
> and Binary Coded Decimal (BCD) in hardware and has the hardware instructions
> to do arithmetic in both binary floating point and BCD.
> I strongly disagree about the suggested motivation for support for
> decimal floating point. It seems reasonable to conclude that the two
> radices address the needs of different markets. Thus, instead of being
> contradictory, they very much could be complementary.
I'm afraid not. The 387 can load and store BCD integers (not floats),
but the internal representation is always base two. A BCD load ends up
being about five times slower than a binary load.
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