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From: Thomas Koenig <tkoenig@netcologne.de>
Newsgroups: comp.arch
Subject: Re: Making Lemonade (Floating-point format changes)
Date: Tue, 21 May 2024 05:49:55 -0000 (UTC)
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BGB <cr88192@gmail.com> schrieb:

> Granted, they are not necessarily the option one would go if they wanted 
> "cheapest possible FPU that is still good enough to be usable".
>
> Though, the point at which an FPU manages to suck badly enough that one 
> needs to resort to software emulation to make software work, is probably 
> a lower limit.
>
>
> Luckily, "uses 754 formats, but with aggressive cost cutting" can be 
> "good enough", and so long as they more-or-less deliver a full width 
> mantissa, and can exactly compute exact-value calculations, most 
> software is generally going to work.

This will require extensive testing and possibly modification for
a lot of software ported to such a system.  This will drive up
the total cost, presumably far more than any hardware savings.

> But OTOH, if 1.0+2.0 gives 2.999999, that is, not good enough, so there 
> is a lower limit here.

An example of a more interesting question is

  if (a >= 0.) {
    if (b >= 0) {
      if (a + b < a) {
        printf("We should never get here!\n);
	abort();
      }
    }
  }