from Hacker News

Reverse Engineering the Constants in the Pentium FPU

by mef on 1/5/25, 7:34 PM with 23 comments

• by lifthrasiir on 1/6/25, 2:24 AM

  I guess the unused entries spell "bad FC" (for floating constant). Also I think constants 6 through 10 are relevant for the decimal-to-binary conversion or vice versa, as evident from the following observation:

      0x5c3bd5191b525a249 ~= 2^123 / 10^17
      0x470de4df820000000  = 2^13 * 10^16

• by garaetjjte on 1/6/25, 2:18 AM

  Fun trivia: for many years Intel documentation was wrong on error bounds in trigonometric functions: https://randomascii.wordpress.com/2014/10/09/intel-underesti...

• by kens on 1/5/25, 7:41 PM

  Author here for your Pentium questions...

• by cmpxchg8b on 1/7/25, 5:00 AM

  Ken, how has the technology for interconnects changed over the years? Seeing all of these disparate regions in 2D it really interests me on how they are routed.