I expect that Microsoft could get some angry customers if Excel's computations varied with the CPU it runs on. Imagine discussing a spreadsheet with a colleague and seeing wildly different data.
Some people would say "That's what you deserve if you use an ill-conditioned algorithm or have an ill-conditioned problem", but most would not even understand that statement.
But doesn’t that already happen? Didn’t we see that when the Pentium flaw was discovered? In fact, I thought there was an Excel spreadsheet you could download and run to test whether you had the flaw or not.
For this argument, the Pentium flaw is not the best example. As long as all CPUs were equally flawed, everything was fine, if you define 'fine' as 'we see the same results on all systems'.
I guess Excel will have the problem in some cases for rare CPUs. For 'common' ones, I expect that Excel contains workaround for errata that might affect its computations.
Well there's a difference between trusting the CPU to get arithmetic right and trusting the CPU to get sin(x) right (or to just know it gets it wrong but not caring).
Some people would say "That's what you deserve if you use an ill-conditioned algorithm or have an ill-conditioned problem", but most would not even understand that statement.