Shading on PI vs. VGX

[devans at SNOWHITE.CIS.UOGUELPH.CA]

Hi!
  I saw some mention of this before, but didn't find a "real" answer.
  I've just begun dabbling in GL with our PI's (4D/25Gs) and wrote a simple
program wich drew a Gouraud shaded rectangle and rotated it.  Things worked
perfectly on the PIs, and the colours were nicely blended to give a "soft"
appearence.
  A while ago SGI Canada lent is a (2|3)40VGX (I say "2|3" because two of the
CPUs were 25MHz and two were 33MHz, according to 'hinv'.)  I recompiled the
same program, and it again worked (MUCH faster!!!! :-))
  BUT.....the shading was very different!  Instead of the soft "blending" I
got on the PI, thje VGX made the rectangle out of stripes (one corner was
green, one blue, one red and one black.)  The colours didn't really mix, and
they sort-of converged on the centre of the rectangle without mixing
together.
  The VGX is long gone now, and I don't recall which version of IRIX it had.
It had the X server, if that's any use......
  This isn't really a pressing problem, just a curiosity.

---->David
devans at snowhite.cis.uoguelph.ca