Mouse and keyboard lag is quite a issue for fast first person shooter games. They tend to get so fast, that my poor PC cannot compete with most, yet still I wonder, if there are tools how to measure the input lag of devices like mouse and keyboard.

For a old-school machine, I use PS/2 ports for both, yet the MX510 Logitech mouse is by original a USB device, connected only by the adapter to PS/2. That make one wonder, if the adapter could not contribute some lag on it's own... (and I think the answer is a definitive yes, it have to)

So that is why I trying to push the PS/2 ports speed up:

...but w/o being able to measure how things get faster, I have no idea if this is helping or not. Default rate is 60, witch seems to be to be awfully low...

There is a great article about it at Anadtech: AnandTech | Exploring Input Lag Inside and Out
...with many hi-fremerate videos to catch the speeds precisely, however any software tools or anything that could be used to determine the lag was not used at all.

There do exist a latency analyze tools for system devices, like this one:

DPC Latency Checker

(showing example of what bad videoplayback is on JetWay V266B mobo (KT266A), because the stupid mainboard pull everything on IRQ7 - that it, on IRQ7 is - GFX card, Sound, NIC card and USB...! Even that FIVE other IRQ's are completely free: IRQ 3, 4, 5, 10 and 11 to be precise.

So, do exist something for the keyboard/mouse that could determine how difference is there between the USB and PS/2 mouse connection? Anyone have any slightest idea about this?