[libre-riscv-dev] [isa-dev] Re: FP transcendentals (trigonometry, root/exp/log) proposal

lkcl luke.leighton at gmail.com
Sat Sep 14 23:25:41 BST 2019

On Saturday, September 14, 2019 at 10:50:15 PM UTC+1, MitchAlsup wrote:

> When you get a multi-generational customer, which has an existing 
> application;
> the first thing that customer will do is to run a sanity check of the new 
> HW implementation using a 
> "reference" benchmark. When any bit of the output of that program 
> mismatches any bit from the
> new implementation, the multi-generational customer will not be able to 
> rationalize that this new
> HW is acceptable or not. This leads to various consternation,..... This 
> happened to me at GOULD 
> S.E.L circa 1982 when the new, faster, HW had more accurate FP 
> implementation. 

rright.  ok.  so let me just check.  it's not the accuracy setting that 
you're objecting to / red-flag-raising, it's the "if less accurate is set 
you're allowed to be *more* accurate", is that correct?

i am reminded of a message by hendrik [allo similarly old person, told ya 
your input was valuable :) ] on iibre-riscv-dev a couple months back about 
how Ahmdahl got similar customer complaints, and had to have an OS patch 
providing *EXACTLY* bit-for-bit the brain-dead broken FP accuracy of the 
mainframe that Ahmdahl were copying.

is this what you're referring to, Mitch?



More information about the libre-riscv-dev mailing list