Strange phenomena

[CS]

So, here is the situation ...

I am looking around in center of a textured cube.
Using ...

glRotatef(aX,1,0,0)
glRotatef(aY,0,1,0)

If aY is near of n*180 i get ~23 FPS
and if aY is near of n*180+90 i get ~93 FPS.

What is causing this?

Other info :
a) Evry side has the same mipmap texture.
b) If i disable texturing i get ~140 FPS at evry aY (and aX) value.
c) I have lighting enabled with one light at eye point

[CS]

I have run several times trough my code, but wasn't able to fix it (instead earned 21 extra FPS http://www.opengl.org/discussion_boards/ubb/biggrin.gif) - so my problem is still actual.

Can You help ?

[amerio]

Humm... Entering the "Twilight zone" ?
More seriously, we may help if you send in a larger piece of code. Might be a "newbie-only bug that can defeat a super-coder"...

You said you win some fps ? How ? (with
such a simple scene???)
Are you sure of your method of measuring fps ?

How do you draw the cube?
How do you set up your texture coordinates?
What hardware is this on?