SyncMaster 633NW FPS issues

[Serekos]

Hello folks at Linus TechTips, i make this because after making some testing i started noticing some weird stuff in my frame rate.

 

I have an old Samsung SuncMaster 633NW monitor with only a VGA output to put at my Graphis Card (Radeon HD 5750); this guy has been reliable for gaming at 720p as it is good for me with antialiasing and anisotropic filtering applied and med to high settings in games; the thing is i started noticing this with the first time i played Battlefield 3 on the system because despite the game setting automatic on high and the game ran choppy and slow, i started fraps and started analyzing different settings and the playable result was normal with some stuff on low wich was weird as the fps counter said the avg framerate was 55fps; then i made explosions, cranked up settings and realized that anything below 50 fps looked like that even with the counter saying 45 or 36 fps in that escene.

 

This problem has been repeated through: Max Payne 3, Dead Space 1, 2 and 3, DiRT 3, Darksiders 2, Far Cry 3, Warface; in other words, every single game i trow at it starts making choppy and the average value of 50 fps and below, my question is. Is the VGA port on the monitor responsible (as it depends on analog converters) or is it the graphics card?

 

I made some stability test on my gracphis (MSi Kombustor) and it went through it without hassle at stock speeds (i had it overclocked before and it began to overheat so i got back to stock, also made a dust cleaning) so my principal suspect is the Monitor.

 

Anyone else have any sugestions?

 

PD: Also noticed that for example in Max Payne 3 as i activated Vsync and locked at 30 FPS i ran good without sttutering, but when it got below it sucked; this applies to other games too.

 

Thanks for reading in advice.