I've been playing Quake 4 since it's release day, and I've noticed there's either a v-syncing or caching issue where the framerate seems to jump for a split second every second or so, I've been calling it a heart-beat all these years.
I first noticed it on my ATI X800 Pro many years ago, assumed it was some weird gpu thing and didn't think much of it. Later I got a GTX 460, while it was much smoother, this weird ticking still occurred. Now I'm using one of the fastest GTX 580s ever made, and seemingly no matter what I do to the settings, I can smooth it out a little, but that micro-stutter is still there every second or so.
Did anyone ever figure out what this was? I've seen this on Intel Cpus, AMDs...Laptops...Desktops...Xeons...Opterons...With SMP, without SMP....I'm not sure what could be causing it outside of just plain bad code that never got addressed.