"Jerry W. Lewis" wrote...
....
WAG alert:
I am not aware of commercial MS languages offering access to the
processor's extended precision (at least not in recent memory), so
it is possible that this cross-platform consistency is due to some
non-standard software extended precision. If so, then this extra
precision on the mantissa and the unexplained limits for MOD may
all be related to fitting this hypothetical custom FP precision
into a convenient word size. It would be interesting to see other
examples that further define the size of the mantissa that MOD must
be using.
....

Warning - some cynicism to follow.

Microsoft's original commercial language was cassette BASIC. It morphed into
BASICA when Microsoft started selling operating systems. IIRC, BASICA had
only one floating point type, and it wasn't IEEE. A quick Google search
leads me to believe it was 4-byte/32-bit. Excel's MOD function dies at 2^27.

The cynic in me is tempted to leap to the conclusion that Microsoft used
it's BASIC/BASICA code in the original Excel for Mac 512Ks in the mid-1980s
and hasn't revised the code since. Surely that can't be?

End cynicism (and sarcasm).

Excel's MOD is clearly *NOT* IEEE-compliant. Why would they target a
non-IEEE virtual FPU?