I think we have some of these issues happening indistinctly on Windows and/or the 360. I get the impression not a lot of people are testing this on the 360 so I will research the console separately since I am programming for the 360 almost exclusively while others are already actively researching the Windows side and report back if I find something meaningful. I must confess I don't see many problems on the Windows side anyway outside of this frame correction and update timing issues. The XBox is handling that fine.

I wonder if some of what we see is related to the XNA refresh since the book was written for the 1.0 version of the framework. I doubt it but it is a possibility. I have had to correct program behavior in Visual Studio after installing it in Vista despite the Vista SP1 patch... so this is not far fetched...

After reading this blog post: http://blogs.msdn.com/shawnhar/archi...-gametime.aspx

I did a little experiment. One thing that stood out was when he says:
"We will call your Update method exactly 60 times per second
We will call your Draw method whenever we feel like it"

So, I just created a bool called drawCalled. I check for drawCalled in Update and only proceed if it is true (I reset to false). In Draw, I set drawCalled to true. It seemed to help quite a bit.

Note that I haven't experienced this issue on the 360, only on Vista.

I just tried a different experiment and it also worked pretty well (again based off what I read in that blog post).

In my Game class, I set IsFixedTimeStep equal to false and things run pretty good now.

-Mark

P.S. In my previous post, I think I meant to use this quote:

"We do the same thing in response to all four causes of slowness:

Set GameTime.IsRunningSlowly to true.
Call Update extra times (without calling Draw) until we catch up.
If things are getting ridiculous and we are too far behind, we just give up."

I was having the same problem with pong, then I changed this

float moveFactorPerSecond = 0.5f * (float)gameTime.ElapsedGameTime.TotalMilliseconds / 1000.0f ;

And now the ball moves right

The original was
float moveFactorPerSecond = 0.5f * (float)gameTime.ElapsedRealTime.TotalMilliseconds / 1000.0f;


Or simple change to

float moveFactorPerSecond = 0.5f * (float)gameTime.ElapsedGameTime.TotalSeconds;

And avoid dividing by 1000.0f to save some processor time (I think)