What is the penalty for stealthing at normal speed?

Question

In both Pathfinder and D&D 3.5e, the rules for stealthing (Stealth, Hide and Move Silently) state:

When moving at a speed greater than half but less than your normal speed, you take a –5 penalty. It’s practically¹ impossible to [use stealth] while attacking, running or charging.

However, none of the rules make any mention about stealthing at normal speed. It is neither impossible, nor is a penalty given. Is there any errata or obscure rule for either system which gives a more official ruling?

^{1 - Pathfinder rules say it's impossible, and D&D rules say it's practically impossible, imposing a -20 penalty.}

Answer 1

The specificity of the Pathfinder rules imply it's impossible to move your normal speed while stealthing, in addition to while attacking, running, or charging.

Note that Paizo is currently playtesting new Stealth rules that cover this situation:

You can move up to half your normal speed and use Stealth at no penalty. When moving at a speed greater than half and up to your normal speed, you take a –5 penalty.

Answer 2

I'd say okeefe is probably right about Pathfinder (though a cutoff between moving your speed and your speed-1 seems silly). My suggestion, would be to either continue the -5 at normal speed, or if you feel the need up it to a -10 penalty (double the 'slower' movement penalty, but half that of running).

Answer 3

Under PF for the Rogue class (page 68 of the Core rules): Fast Stealth (Ex): This ability allows a rogue to move at full speed using the Stealth skill without penalty.

As others have said, from greater-than-half-speed to less-than-full-speed, the penalty is -5. Personally, I have run it as -5 for (51% to 75%) speed and -10 for (76-100%) speed ... unless the character has Fast Stealth.