Latency compare USB to PS/2 ports?

Discussion in 'Hardware Discussion & Support' started by caps_buster, Sep 22, 2013.

  1. caps_buster

    caps_buster Just one crazy geek :)

    Oct 20, 2012
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    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?
  2. mkk

    mkk Well-Known Member

    Oct 9, 2003
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    For what I've seen and read there doesn't seem to be any major issues at the interface side . Although a pure PS/2 connection has the theoretical advantage you'll only see keyboards use that today, and not for the sake of reducing latency. Apart from the report rate (which many gaming mice can turn up towards 500 or even 1000 times a second) the sensor itself can be a cause for latency. Then there's always the corded vs wireless question.

    If you have a mouse that you suspect have internal or connection latency, you can compare two mice on your own system by this little practical test:
    If one mouse has significantly more latency than the other it will show over the course of a dozen or so test runs.

    All too oftenly over the last few years I've find instances where the input handling of a game has been the problem, much more often than the hardware.
  3. Matth

    Matth Flash Banner Hater

    Jun 22, 2002
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    I doubt that the PS/2 adapter is active, most USB + PS/2 dual mode mice will recognize the connection type and operate in the appropriate mode, and the wiring conversion is not necessarily standard, so make sure you kepp the device and its own adapter together.
  4. WxMan1

    WxMan1 Active Member

    Dec 26, 2007
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    I may not be current on the current stuff, but in the olden days latency pertained to how long any arbitrary device could hog the bus. In the olden days there were lots of issues pertainting to audio clipping and hanging / shredding display.

    In those days the default 'latency' of the AGP bus was 254. So all sorts of 'patch' were released to address that. One of the big ones implemented Oda's technique to alter the motherboard resource register.

    On my ancient PIII-1400S TUV4X platform supporting Win 2003 I've implemented PCI Latency Tool.

    I've set default latency - in BIOS - to 64, and have set AGP latency to 128.

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