USB endpoints limitations... - Page 1
Forum section: electronics / projects

author: technix
author_rank: Super Contributor
timestamp: March 19, 2018, 06:22:49 pm
content: Have anyone of you ever ran into the USB endpoint limitation of your motherboard?I have most of my debug probes living on my desk, all plugged in by default. Now from time to time I see the operating system popping up a small prompt saying that the device have not enough resources. Have any of you ran into such problems?My motherboard is based on the Intel Z97 chipset. It appeared that this chipset in question have a limit of 96 endpoint on its internal USB 3.0 XHCI controller.

author: fourtytwo42
author_rank: Super Contributor
timestamp: March 19, 2018, 06:29:32 pm
content: I think mentioning your OS might be helpful

author: ogden
author_rank: Super Contributor
timestamp: March 19, 2018, 06:36:21 pm
content: Quote from: technix on March 19, 2018, 06:22:49 pmHonestly it is very unusual to hit 96 endpoint limitationHow many USB devices and endpoints you have? Motherboard model? Do you use external USB hub(s), are they powered? It could be so that you are hitting not endpoint, but USB power limitation.

author: ataradov
author_rank: Super Contributor
timestamp: March 19, 2018, 06:42:13 pm
content: It is not endpoint limitation, but rather bandwidth limitation. Host has to reserve a certain amount of bandwidth for control and isochronous endpoints, so even if you don't send any data, the bandwidth is allocated and wasted.

author: technix
author_rank: Super Contributor
timestamp: March 19, 2018, 07:33:35 pm
content: Quote from: fourtytwo42 on March 19, 2018, 06:29:32 pmmacOS High Sierra.Quote from: ogden on March 19, 2018, 06:36:21 pmIhave close to 20 devices on there, on a Gigabyte GA-Z97M-D3H motherboard. I have quite a few hubs but all of them are externally powered, except the one built into the Apple USB Keyboard.Quote from: ataradov on March 19, 2018, 06:42:13 pmFor a USB 2.0 capable controller with a lot of USB 1.1 devices attached, it is hard to run out of bandwidth.

author: tszaboo
author_rank: Super Contributor
timestamp: March 19, 2018, 07:50:29 pm
content: Then again, you should be lucky that your system works at all, since you violated the EULA and hacked it together.

author: ataradov
author_rank: Super Contributor
timestamp: March 19, 2018, 07:56:53 pm
content: Quote from: technix on March 19, 2018, 07:33:35 pmI'm not sure how the bandwidth is actually allocated by the OS. If macOS has something like dmesg, then run it. Linux is very explicit in what kind of resources it is running low on.

author: technix
author_rank: Super Contributor
timestamp: March 20, 2018, 05:49:11 am
content: Quote from: NANDBlog on March 19, 2018, 07:50:29 pmQuote from: blueskull on March 19, 2018, 07:59:58 pmI do have multiple macOS licenses in the first place, owning two MacBook Pros. This problem applies to both the hackintosh and the Macs given the same chipset series. It also applies regardless of OS - actually macOS handles it a lot better than Windows.

author: technix
author_rank: Super Contributor
timestamp: March 20, 2018, 06:20:02 am
content: Quote from: ataradov on March 19, 2018, 07:56:53 pmAFAIK the debug probes runs the endpoints dry fast. I have five of them attached: a MiniPro TL866A, an ST-Link v2, a PICKit 3, an Atmel ICE and a J-link v9 clone.

author: Bassman59
author_rank: Super Contributor
timestamp: March 20, 2018, 06:21:24 pm
content: Quote from: blueskull on March 20, 2018, 05:56:31 amYou are quite the moral relativist, aren’t you.