[SOLVED] USB Bandwidth/Power concerns

Oct 14, 2018
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So I've been reading some stuff about USB bandwidth + power and have a few concerns. The only issue I've ever had was when I switched from HDMI to DP on my OG Vive since a gfx upgrade. I used to get a quick black screen flash while playing beat saber every few minutes. The solution was to go through Device Manager and uncheck "Allow the computer to turn off this device to save power" on every single device.

So everything was fine until I got a wireless keyboard. The wireless USB adapter would cause the weirdest issues and now that I found out more info about USB bandwidth and power consumption, had found that the wireless USB adapter for the keyboard uses 500ma! More than likely the source of all the strange issues once I got the new wireless keyboard. I solved this by plugging in the wireless adapter into a USB-C to USB adapter. I'm assuming the USB-C slot had a lot more bandwidth/on a different motherboard USB hub.

Now I've been researching a lot but not really getting much more info than actual USB bandwidth, which would be a slow thing not power issue. The most info I found is that each USB can provide 500ma and that most devices are only 90-100ma.

**My main concern is...** will Pimax cause any power issues and how can I figure out more about USB power consumption? I used USBDeview which is excellent, shows each USB and exact power usage but I don't know what device is on what motherboard hub or **how to find exact limits**. I have every single USB on my computer plugged directly into the back/directly into motherboard. No external hubs or anything. A few 5ft and 15ft USB extension cords. A total of 9 USB devices plugged in at all times.

I think the best solution would be something like this: https://www.amazon.com/gp/product/B00FPIMICA
Would this basically eliminate any power consumption issues? Just plug in any high usage devices in this bad boy?

Any ideas/suggestions/info?
 
The USB specs you are supposed to be able to rely on are that a single USB2 port can supply 5 VDC power at up to 0.5 A, whereas a USB3 port (and that includes the new type C port which is used only on USB3) can supply up to 0.9 A. On a mobo, EACH USB port can do this - there is no real "Hub" on a mobo. So if you are not using external hubs and using only the mobo ports on its front and back panels, those are the limits.

Regarding bandwidth (which you suspect probably is not involved here), the bandwidth of the new USB3 system is MUCH higher than the USB2 system. BUT that applies only if you are using a UBS3 port with a USB3 cable and a USB3 device on the end. Plugging a USB2 device into a USB3 port, or using the wrong cable there, will only yield USB2 bandwidth. Likewise, using a USB3 device even with a USB3 cable on a USB2 port also will give you only the slower speed. For example, when you used an adapter to connect the USB2 wireless keyboard system to a USB3 Type C port, you still get only USB2 bandwidth for that device, although its power source now can supply up to 0.9 A.

A further note on the use of external an Hub - which you are not doing right now. Regarding power, you really need to use a hub that has its own included power supply device able to provide all the power needed for all its output ports. For example, if you get a USB3 Hub with four USB3 ports, its power supply module should be able to supply at least 3.6A at 5 VDC. (Now, sometimes this gets confusing because the power module may have 12 VDC output and its specs are in terms of Watts. The Hub converts the power supplied. So four output ports at 5 VDC and 0.9 A each needs at least 18W, which is 1.5A minimum at 12 VDC.) IF you get a Hub that includes so-called high-power Changing ports, it power supply module should he capable of more to meet those higher output specs. On the bandwidth side, when you use a Hub ALL of its ports share the bandwidth of the ONE host port on the mobo to which the Hub is connected. Normally this is not a problem because often you are not using two or more high-bandwidth devices on the Hub at the same time, but it can be an issue in certain configurations.
 
Oct 14, 2018
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Got it, thank you.

Do you happen to know what motherboard USB hub maximum power is? or how to tell which usb cable shares which hub?
 
It differs by manufacturer and even motherboard.
There are specifications like USB 1.x and 2.0 should provide a 5V to power connected USB devices.
USB 2.0 100mA (500 mA max per hub) and USB 3.0 150mA (900 mA max per hub).

I have found some motherboards cannot deliver that amount and some others go out of specs by delivering higher current than the max specified.
I have a couple of USB 2.0 ports that deliver 500mA and the USB 3.0 delivers 1500mA.


 

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