Bob Jones wrote:
You can set the internal precision of the x87 unit to 32, 64 or 80 bits, it just defaults to 80, and as there's little if any performance difference between the 3 modes, thats how it's usualy set.
Despite those settings, the fpu still holds intermediate calculations to 80 bits. The only way to get it to round to the lower precision is to write it out to memory then read it back in. This, of course, is disastrously slow.
There's no good reason to "dumb down" floating point results to lower precision unless you're writing a test suite.
