I´ve been searching in the forum, but believe me, i didnt found the answer for my problem yet:

1) when running a level with just a ball and a camera, in fullscreen mode, and apply a force to the ball (phent_addcentralforce), the movement / displacement its not smooth. It seems the last frame of the ball movement its always visible. (the problem occurs in Techdemo camera movement also);

2) in fullscreen mode, the FPS [F11] dont exceed the monitor refresh rate (max refresh rate at 1280x1024 its 72 hz);

3) in window mode, the FPS its better (120 or more), however, its almost impossible play the game, because theres nothing smooth in that level;

4) with 70hz refresh rate, i obtain the best results, however still happens those "frames" or "jerks" in the game;

5) i made a test: with another monitor (Samtron CRT 75E), the problem its the same;

6) My system:
Athlon 1.15 GHZ
512 MB RAM
3dCard: Asus v9570 TD 128 MB Geforce fx 5700, BIOS: 4.36.20.21.00, updated drivers
Monitor: TFT Samsung synchmaster 172s, updated drivers
Directx 9.0c, dxdiag-directDraw test=OK, direct3D=OK
3dgs a6

7) well, sorry my english...but i need some help...thanks.

Not sure if this is the problem for you, but for me it was Vsync.
If you're using Nvidia Forceware drivers enable Vsync and see if that makes a difference. Then you can drop the refresh rate back down to 60 and it will still look the way it should without the jerks or waves.

Thank you for the reply Daedelus, but the problem its the same with Vsynch enabled...

If the engine is really spluttering like a car (if that's what describes it ) I'd have a look for viruses and other malware on the system. I once had this problem with several other game engines and I found out all the EXEs on my HDD were infected with a virus!

As for the Refresh-rate, I haven't got any clue why this popular bug exists in A6. It sure is a directX+nvidia cards issue, nevertheless in other engines, they must have found a workaround...

Well, i realy think theres a bug somehere. i made another test: installed a fresh A6 trial in another computer and the problem its equal, even with techdemo! i cant believe it! this other computer has winXP, Gforce fx 5200, AMD processor, 512 MB RAM, monitor Samtron CRT 75E.
By the way, i have no problems playing games in my computer, like pro evolution soccer (in fullscreen and window mode), fifa 2005, and all type of games are fine. Just with A6 i have problems, i just dont understand.
So please wheres the bug? Any clues?...
I think this way im not going to make no games at all in A6 engine...

Well, after hours testing, i think i found a way to workaround this problem, but with limitations. Including TIME_SMOOTH=0, FPS_MAX=70 (70hz its the monitor refresh rate), and FPS_LOCK=ON. with this code the movement appears to be smooth, but i cant change FPS_MAX to a diferent value.
I really appreciate someone please could explain to me why these situation occurs?

Well I'm only willing to leave the "it's all caused by a virus!" spree if you tell me you've also checked the key.exe file on your diskette for viruses since in my case, that was were the virus survived longest and it gave me real headache till I figured why even brand new A6 installations didn't actually solve it

In the performance & quality settings for your nvidia did you set up a custom profile to add v-sync to your game or did you use the global settings ID to set v-sync? I found that on my computer setting up a custom profile did not always work on some games including the 3dgs engine. Not sure if it's just my computer that does this, but I thought I would post it. My drivers are updated(need to update profile)