double rounding in x86

[Chris Hinds]

Samuel A. Figueroa <uunet!SLINKY.CS.NYU.EDU!figueroaauunet.uu.net> writes:

> Incidentally, on a Motorola 68K series chip, you also pay a price
> for "exact-bit agreement," though I don't know what that price is.  (On a 68K
> chip, you simply set the precision mode to the desired precision, and you're
> done.  Just sit back and relax, as each floating-point operation will now take
> more clock cycles than before.)

True statement for a 68681 or 68682. However, on the 68040 and 68060 the
penalties for emulation of a single-precision or double-precision machine
were eliminated. In other words, setting the rounding precision to single
or double does not degrade performance of native instructions or emulated
instructions.

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