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Thread: USB bus speed

  1. #1
    150+ Forum Groupie mach7's Avatar
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    USB bus speed

    Hello...i have my main computer running my Captain and First officer instrument panels along with a whole bunch of plug and play units. I am finding that my engine gauges (mechanical gauges modified with USB servo motors run off OC Sioc boards) will "hang" up a bit during engine acceleration and deceleration.

    I am attributing this to a lot of traffic on the USB network.

    Can I use one of my client computers running an outside view using WideView to handle a couple of the plug and play units? Or do these items have to be driven off the server computer?

    If no...is there anyway to increase the USB speed?

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    150+ Forum Groupie mach7's Avatar
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    Re: USB bus speed

    The above question was asked due to the fact that my CPU usage went to 100% in the middle of taxiing out for take-off and i basically lost all of my plug and play devices...my go-flight MCP froze...and then only displayed a couple of digits...and my engine gauges began to stutter....i had to reset the entire system!

    I have since (hopefully) solved this issue by doing a couple of things.....first I deleted my virus protection software (not connected to the internet on this PC anyway) as I was suspicious that it might have tried to start a disk scan in the middle of my flight.

    Second...I set the affinity level on my performance task bar to spread the CPU usage over both cores..as everyone is painfully aware that Fs9 only takes advantage of one core...i found this neat trick online to fool it into using both cores;

    Select FS9 in windowed mode...

    CTRL+ALT+DEL to get to the performance tab...

    right click on FS9.exe....

    select 'set affinity'

    deselect CPU 1 and leave CPU 0 selected...

    enter 'ok'

    right click on FS9.exe again and repeat...(deselect CPU 0 and reselect CPU 1...then repeat and select both CPUs)

    This will allow FS9 to spread across both cores and will be confirmed by viewing the CPU usage.

    My system now runs at 52% in the 'windowed mode' and as high as 75% in the full screen mode.

  3. #3
    glider pilot Brodhaq's Avatar
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    Re: USB bus speed

    Hello! I have spent a LOT of hours by debuging USB wired instruments in our generic IFR trainer at our university this year... We use GOFlight units (3x radio, 2x buttons, 2x switches, 1x MCP) and 19 gauges from Simkits. I had various experience - from sometimes freezing and shuttering instruments up to completly crashing the USB bus (windows USB removed sound), or extreme CPU usage. The problem was caused by some system driver which was overloaded by "overaddressing" the USB devices. Windows can handle up to 128 devices on USB bus but no specification talks about the USB topology - the USB hubs and such stuff. We had modern high quality powered USB2 hubs and still problems. The solution? NEVER EVER connect one USB hub into another. It might work for 100 hours smoothly but one day the driver will fail - sometimes it will be seen as just freezing of gauges for few seconds, sometimes you will head the windows USB removed sound and the whole USB bus will go down until you restart your PC. Interesting fact: probability of hub overload increases with CPU overload (try setting all your graphics sliders to the right ) and with USB traffic (try doing some aerobatics which will cause the gauges to display rapid changes in attitude, speed, vertical speed and such).

    I tried monitoring USB traffic but no results seemed to be noticeable when my bus crashed - no peaks in traffic.

    My observations: software tweaking has almost unnoticeable effect, hardware topology has big effect but the best thing is to buy USB2 extension cards to your PCI slot which will provide you "new" USB ports. To every of "native" USB port on your computer (either on motherboard or on the PCI card) connect just ONE 7-port USB hub. It means you will always have 7times more USB ports than you have on your computer case. Do not try splitting the USB hubs further, it will bring just trouble.
    Another observations: some devices (Simkits gyro heading indicator for example) dont like USB3. We had 2 instruments connected to USB3 (I didnt notice they were USB3) and they showed random failures, delays and so. As soon as I connected them to USB2 ports they worked very well. And even if you connect the USB2 hub into USB3 port, the line will still be "bad" for some devices. However other might work well.

    Now I have about 8 USB ports on computer case and 7-port hub in each of them and there are NO failures, everything is stable. Good luck!

    Pavel

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    150+ Forum Groupie mach7's Avatar
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    Re: USB bus speed

    Pavel, this in invaluable information...thank you very much.;

    I have one question for you regarding your comment NEVER EVER connect one USB hub into another. On my current setup, I have two USB hubs, each connected to there own (separate) USB connection at the back of the computer. This should be OK correct?

    I am assuming in your statement you are referring to someone that plugs in one USB hub to there PC...then connects an additional USB hub to the first (already connected) USB hub (sort of daisy chains the two together) (?).

    Again...this is very good information..thank you very much

    -Jim

  5. #5
    glider pilot Brodhaq's Avatar
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    Re: USB bus speed

    Hello,
    exactly. Connecting as many hubs to PC is ok, but if you connect a hub into a previous hub it could cause trouble.

    Regars,
    Pavel

  6. #6
    150+ Forum Groupie mach7's Avatar
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    Re: USB bus speed

    Thanks Pavel...I'm golden then as I have two USB hubs...each with 7 devices connected, but connected to there own USB socket on my PC.

    Thank you again for the info and research

    -Jim