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PS/2 faster than USB, what about CPUs & OS?

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  • User profile image
    androidi

    I was reading a Kinect review and thought: I'd buy it if it has the latency of PC keyboard/mouse. Then I thought about, well USB can't possibly be faster latency wise since it's more complicated and general. Google found me this study that has timed PS/2 vs USB and PS/2 is indeed faster.

    http://superuser.com/questions/16893/do-usb-or-ps-2-keyboards-respond-faster

    http://brm.psychonomic-journals.org/content/34/2/250.full.pdf

    Now another interesting question would be, which CPU architecture has least latency and are there other things than that which PC buyer should look into when building low latency system? (for user input purposes such as gaming)

    Also, which OS is best for arcade gaming? How does Windows 7 end to end latency compare to XP? The issue here is that I noticed a huge drop in perf on XP when upgrading to a GPU that didn't have 2D chip/acceleration so going back to older OS with these new cards is no solution.

     

    I believe hardware testing sites should have a benchmark that looks at the whole system. By adding a microcontroller in-line with keyboard or mouse, one could time when the input arrive and at same time have light sensor attached to the CRT where the Windows Explorer will pop up. I can already tell that it will reveal Windows 7 to be much slower than XP since I can see that without any tools. - The unknown is the rest of the system so a lot of components from various vendors need to be tested.

  • User profile image
    W3bbo

    I believe hardware testing sites should have a benchmark that looks at the whole system. By adding a microcontroller in-line with keyboard or mouse, one could time when the input arrive and at same time have light sensor attached to the CRT where the Windows Explorer will pop up. I can already tell that it will reveal Windows 7 to be much slower than XP since I can see that without any tools. - The unknown is the rest of the system so a lot of components from various vendors need to be tested.

    This is just a trend we've been seeing ever since Windows XP hit the scene; fewer developers (and hardware designers) are paying much attention to latency, so the user-experience suffers.

    I think it's naive of developers to think that faster CPUs (and modern systems in general) means lower latency; it actually means faster throughput.

    I imagine a modern computer with modern hardware and operating systems will be considerably laggier compared to a typical late-1990s machine running Windows 98 or 2000:

    • As the links pointed out show, USB mice/keyboards have longer latency than PS/2
    • TFT panels have a much larger input-lag than CRTs, usually under 30ms, but sometimes as high as 80ms, then factor in pixel response-times too
    • Windows' is getting more complicated all the time, and recently things like GDI hardware acceleration have been removed. If you want to see real lag, check out SQL Server Management Studio 2008 R2 on Windows 7 with Aero enabled (the latest version as I write this). I'll put a lot of this down to sloppy WinForms code used in the product, but the fact is it's still there. Another example is Visual Studio 2008's Solution Explorer (and UI in general) flickering a lot when Aero is enabled.
    • Then you've got applications running on top of the system, usually WinForms is fast, but what of WPF? There's a lot of delay in many WPF programs I use, such as VS2010.
    • Finally, with the move to the cloud and non-local data storage, I expect cheap l'll applications will be built on the assumption that the data server is <50ms away and won't bother showing asynchronous loading dialogs.

    It's kinda sad when a 10 year-old computer gives a better and more fluid experience than a modern one.

  • User profile image
    JoshRoss

    I've never had any latency issues with Zork. But then again, it uses the most advanced graphics processor available, my mind. -Josh

  • User profile image
    Cream​Filling512

    Pretty sure USB is fine for human input devices, I wouldn't be concerned about latency below 100 ms.  If latency really matters, you need a real-time OS running with interrupts shut off.

  • User profile image
    androidi

    @CreamFilling512: "Pretty sure USB is fine for human input devices, I wouldn't be concerned about latency below 100 ms. "

    Just quoting for laughs. Like "640 KB is enough". Atleast with decently fast, low latency mass storage/network, that RAM can be "fine", rest can be streamed/uncompressed on fly.

    Try add some lag (90 ms?) to your mouse input. I claim that the more latency in the mouse input, the larger the icons/hit targets need to be to comfortably hit them, especially with some small laptop pad, since any error in the input and you need to do a second input. So maybe 100 ms is fine if all you need to do is few inputs and you do those from memory. That's a bit limiting if you're doing a lot of input partly from memorization and part from visual cues.

    The point here was, with every component in system starting to add little bits of latency here and there, it adds up for a human noticeable end-to-end latency.

  • User profile image
    dentaku

    Except when dealing with anything that makes sound where small latency is the most important factor. In that case, the difference between 18ms and 7ms is noticable.
    Musicians go to great lengths to get latencies as small as possible.

    , Cream​Filling512 wrote

    Pretty sure USB is fine for human input devices, I wouldn't be concerned about latency below 100 ms.  If latency really matters, you need a real-time OS running with interrupts shut off.

  • User profile image
    aL_

    100 ms is a really noticable lag.. especially for gaming. just think of it as playing a game at 10 fps Smiley

    as for usb though im not sure. 2002 is a pretty long time ago and controllers are constantly improving. also im not sure latency is really part of the usb spec, the time it takes for the mouse to register a click is one thing but the time it takes for that data to travel across the wire seems like it would be a question of bandwidth.. the mouse is sending data continuously after all, higher bandwidth means higher pollrate

    also, usb is used for things that require far higher bandwidth and far lower latency than hid devices such as harddrives or indeed audio devices Smiley

  • User profile image
    joechung

    I use USB keyboards and mice all the time.  Not sure why you think it is just for hard drives.

    As for bandwidth, wireless Bluetooth can handle HID fine so I'm sure wired USB can too.

    Anyways, the UI latency you've noticed is likely caused by application-level latency, not hardware-level or driver-level latency.  It's easy to see this if you play a game with light system requirements.

  • User profile image
    W3bbo

    , joechung wrote

    I use USB keyboards and mice all the time.  Not sure why you think it is just for hard drives.

    As for bandwidth, wireless Bluetooth can handle HID fine so I'm sure wired USB can too.

    Anyways, the UI latency you've noticed is likely caused by application-level latency, not hardware-level or driver-level latency.  It's easy to see this if you play a game with light system requirements.

    I remember there was a backlash from gamers as USB mice were introduced because of the way USB device polling worked. Apparently you can increase Windows' polling rate from the default of 125Hz (the DirectX mouse utility reports mine is 127Hz, oddly enough).

  • User profile image
    aL_

    @joechung:

    well yeah me too, i think you misunderstand me Smiley what i mean is that since usb is used for far more latency intensive stuff, handling hid devices should not be a problem, atleast not on the bus side of things.

    many higher end gaming mice allow you to increase the poll rate well beyond the 125 hz (mine goes to 1000hz). still 125hz only means an 8ms delay but is still noticable as pointer choppyness/inprecision

    That not an aspect of usb per-se but how the mouse driver is implemented. usb can handle that and far more. a hid packet is what? at the absolute max 1k? (probably far less in reality) that would make for a theoretical maximum of 60 mhz poll rate (minus 10-15% overhead of controller-device communication)

    as for latency in "new computers" i'd chalk that up to software more than hardware. Smiley

  • User profile image
    androidi

    There's a driver (usbhidf) that, with driver sig. enforcement disabled on 64 bit OS, may allow to greatly 'overclock' the mouse polling. TMNF that I play now and then is played with keys / pad though and on the more challenging/fast user made tracks just the any decent latency gets really noticeable (atleast if you can compare it on systems that have large difference there), which lead to asking what else could be looked at beyond using CRT. Now if I really really wanted to win I could cheat but that game is just too much fun to actually play, so next best thing is to improve the system latency. This game doesn't care about network latency btw.

  • User profile image
    magicalclick

    I would worry about about my GPU performance and my internet lag when gaming. Those are much more noticeable than a few feets of USB wire.

    Leaving WM on 5/2018 if no apps, no dedicated billboards where I drive, no Store name.
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  • User profile image
    PerfectPhase

    @aL_: Bandwidth and latency are not connected, it's possible to have high bandwith and high latency.  I have no point other than that, just thought I'd mention it Smiley

  • User profile image
    aL_

    @PerfectPhase

    i agree in the general sense, RDram is a great example of that. but there are many diffrent sources of latency, for a mouse there is the time it takes for the controller to send a packet to the mouse and for the mouse to respond, but there is also the rate at whitch this can happen. the latter is affected by bandwidth.

    i would note though that all usb controllers/drivers andusbchips in mice are not alike, simply switching to a new motherboard might significantly improve latancy Smiley

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