Problems with USB 3.0 - not enough resources

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DaveB
Posts: 78
Joined: Sat Sep 05, 2020 10:32 am

Problems with USB 3.0 - not enough resources

#1

Unread post by DaveB »

Believe it or not - you can't run four USB devices on a single USB 3 hub without the possibility of running into problems.

I came across this when setting up my new PC. This has 2 x USB 3 on the front, 4 x 3.0 USB and 2 x USB 2.0 on the back that come off the motherboard. That is nowhere near enough for what I need - which is to run 3 x SDR and 3 x USB HDD plus a wireless keyboard/mouse and 64Gb USB stick for file history. So I added a PCIe 4 port USB 3.0 card.

In my initial setting up - I added the various devices and tested them one by one - only to get an error message saying there were insufficient resources to run the USB device - after adding another device.

I googled the error message and it turns out because of the way resources are allocated under USB 3 there a (to me) severe limits on how many devices will run together on one hub.

Let this link explain it https://helpdeskgeek.com/help-desk/how- ... indows-10/

The most recent problem I had was when I added a 4th SDR - just an RTL-SDR dongle. As soon as I started it up the audio on another SDR receiver that was running went 'choppy'.

I worked round the problem by re-arranging which devices go into which controller in order to spread the load. So the two SDRplay devices go into the USB 2.0 ports, the wireless keyboard dongle goes into a front panel USB 3 port (mostly because the mid-tower case blocks the signal if it is plugged in the back), and the other stuff is split between the USB 3 ports at the back.

Now I can run the three main SDRs at full bandwidth (#3 is an Airspy mini) and record the streams simultaneously without problems.

So if you get a problem with a 'bad' USB 3.0 port - it might be a lack of resources.

DaveB

Max
Posts: 858
Joined: Thu Aug 13, 2020 9:47 am

Re: Problems with USB 3.0 - not enough resources

#2

Unread post by Max »

Dave

You might want to look at something like this if you need more resources in future:

https://www.startech.com/en-gb/cards-ad ... exusb3s44v

Don't know where you are but in UK this is 85 GBP on Amazon.

73

Max

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KA1GJU
Posts: 264
Joined: Tue Aug 11, 2020 2:16 pm

Re: Problems with USB 3.0 - not enough resources

#3

Unread post by KA1GJU »

My Super Station #4 server runs 2 Airspy HF+'s, 1SDRPlay, 1 SDR-iq via a powered hub from one port. On the opposite side of laptop I have an IC-7100 remote base. No issues so far!

73 Kriss KA1GJU
73 Kriss KA1GJU Home of the KA1GJU Super Station SDRC Servers in NH, USA (FN42mw & FN43na)

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Simon G4ELI
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Re: Problems with USB 3.0 - not enough resources

#4

Unread post by Simon G4ELI »

Max wrote: Thu Nov 19, 2020 11:30 pm Dave

You might want to look at something like this if you need more resources in future:

https://www.startech.com/en-gb/cards-ad ... exusb3s44v

Don't know where you are but in UK this is 85 GBP on Amazon.

73

Max
Not cheap! I prefer a powered hub with a ~2m cable so I can get the devices away from the PC, but it is powered and up to full spec. per port.

An alternative is to slaughter all people/companies which make USP SDRs and don't off a 5v/12v input.
Simon Brown :shock:
www.sdr-radio.com

Do not send me direct e-mail, thank-you!

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PD3LK
Posts: 517
Joined: Thu Aug 06, 2020 10:36 am

Re: Problems with USB 3.0 - not enough resources

#5

Unread post by PD3LK »

works fine and cheaper (but do connect the card to the PSU)
https://nl.grandado.com/products/supers ... YcQAvD_BwE

DaveB
Posts: 78
Joined: Sat Sep 05, 2020 10:32 am

Re: Problems with USB 3.0 - not enough resources

#6

Unread post by DaveB »

I've got this one from Startech - PEXUSB3S4V USB 3.0 PCIe card at £27.66 from CCL computers. And it has been plugged into the PSU -I checked when the PC was delivered

The 'lack of resources' isn't to do with the power, despite the article saying plug power hungry devices into USB 2.0 ports - its to do with the limited number of 'endpoints' - at which point myknowledge stops. All I know is they explain some USB devices use lots of them, so not so many. So if you have 4 'endpoint hungry' devices plugged into one hub it will give problems. It also explains that a hub plugged into a USB 3.0 will only have the 'end point resources' of a single USB port.

DaveB

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PD3LK
Posts: 517
Joined: Thu Aug 06, 2020 10:36 am

Re: Problems with USB 3.0 - not enough resources

#7

Unread post by PD3LK »

it's proberbly a lack of available interrupts, that's a hw limitation on the motherboard.

Max
Posts: 858
Joined: Thu Aug 13, 2020 9:47 am

Re: Problems with USB 3.0 - not enough resources

#8

Unread post by Max »

There are loads of perfectly satisfactory powered USB 3.0 hubs available, but the question was about throttled resources which on most hubs is one controller shared between all ports, so slowest device connected (USB 2.0 perhaps) can drag down performance of all the others. That's my understanding anyway. Joanne has written very clearly and at length about this elsewhere on the old IO Group. Sorry, I haven't the time to search for it.

The one I posted offers four totally independent and full USB 3.0 spec to each port (one controller per port), hence the price! "You pays yer money and you takes your choice" as we say here in the UK!

73

Max

jdow
Posts: 799
Joined: Mon Aug 10, 2020 8:17 pm

Re: Problems with USB 3.0 - not enough resources

#9

Unread post by jdow »

Sigh, Gigasigh.... When trying to calculate what your bus can handle in terms of devices calculate the TIME they take on the bus. An RTL dongle at 2.4 ksps is pulling down about 40 megabits per second of data. With overhead considered at USB2 speeds, all it can do, this comes closer to 45 megabits per second of 480 megabits per second capacity. Be generous and presume it uses 10% of the bus. Perform this calculation for all the other devices. Four rtl devices should work rather easily. I do that daily. An AirSpy HF+ has a higher bits per sample and lower sample rate. I'd expect it to be within the range of bus usage of the RTL dongle. A hypothetical front end that used 16 bit samples and 2.4 Msps would use about 20% of the bus. A single AirSpy R2 with 12 packed bits per sample eats over half the bus, and usually seems to cause USB2 buses to pack up and die. With unpacked samples it is up at the practical limit of the bus.

In other words each device uses X amount of TIME on the bus. Some at USB3 will work faster; but, the bus slows down when talking to the USB2 devices.

You also have power issues. And some #@$(&@)(#& a**hole invented an unpowered USB3 hub, as I found out for myself the painful way. They will NOT power many devices on their ports. RTL dongles allocate half an amp. (They actually use somewhat less.) Other devices ask for their power. Learn the numbers add them up. And use ppwered hubs anyway.

Now analyze your needs (and budget) and plans. If you have big plans for the future the StarTech four controller USB3 card is EXCELLENT. If you have more casual plans a really cheap USB2 plugin card with powered hubs can run your rtl dongles. I'd use a powered hub with a 3 amp or better power supply, though.

I am running an amazing collection if things on one USB2 bus using an array of hubs. 4 RTL dongles, two cheap USB audio dinguses, an RS485 device polling a GPS clock, and on and on. Not all of them are in use at any given time. But I've not run out of time yet. Power - powered hubs and distributing devices with malice aforethought solves that problem. For AirSpy 10 msps beasts I have a StarTech card, one port per AirSpy. Left over ports run backup disks etc.

{^_^}

DaveB
Posts: 78
Joined: Sat Sep 05, 2020 10:32 am

Re: Problems with USB 3.0 - not enough resources

#10

Unread post by DaveB »

Max wrote: Fri Nov 20, 2020 11:39 am There are loads of perfectly satisfactory powered USB 3.0 hubs available, but the question was about throttled resources which on most hubs is one controller shared between all ports, so slowest device connected (USB 2.0 perhaps) can drag down performance of all the others. That's my understanding anyway. Joanne has written very clearly and at length about this elsewhere on the old IO Group. Sorry, I haven't the time to search for it.

The one I posted offers four totally independent and full USB 3.0 spec to each port (one controller per port), hence the price! "You pays yer money and you takes your choice" as we say here in the UK!

73

Max
I'll keep in mind the possibility of the more expensive Startech hub if ever I have to upgrade to an SDR that has 20MHz or more bandwidth and run into problems. If I need more ports for USB 2.0devices I'll invest in a cheap backplane with 4 x USB 2.0 sockets and plug into the unused header on the motherboard.

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