Maximum number of block erupters raspberry pi can handle?

I'm trying to figure out where the bottle neck in terms of bandwidth would be.

Assume:

no other processes running on raspberry pi (700MHz processor, no overclocking)
no limit on internet up/down rates no limit on power of external USB hub (5V, 12A power supply)

What is the maximum data rate that the usb bus can handle? What is the maximum data rate a block erupter could ever need (I don't know how to convert Hashes/s to Bytes/s on the USB bus)

Are there tools I can use to grab these numbers (e.g. some utility like netcat?)

Can I put a 10-port usb hub in each of the two raspberry pi usb ports?

asic

tarabyte

Posted 2013-10-28T17:46:17.150

Reputation: 219

what USB hub are you using? – Phill Pafford – 2014-03-12T01:32:53.413

Answers

You can probably go up to the maximum of 127 devices if you really wanted (the USB2 limit), remembering though that the Ethernet adaptor is one, and each hub also counts in one. Word on the street also indicates a 49 Eruptor limit, though that's probably just a software limitation.

The transfer speed will never be an issue.

The CPU speed will never be an issue.

Anonymous

Posted 2013-10-28T17:46:17.150

Reputation: 211

Unfortunately, the rPi does not have a full USB firmware controller implementation and cannot handle multiple levels of hubs. Some single hubs exceed this by themselves (because they're internally implemented as more than one hub) and that's why "cascaded hubs" don't properly with the rPi (some ports are dead). – David Schwartz – 2013-10-29T01:44:11.990

I've not seen this. In my own testing I've gone a few levels deep and had no problems with all the devices. My Chinese USB drive RAID was dirt slow, but that's a whole other story. – Anonymous – 2013-10-29T01:53:36.063

so it looks like only 8 (4ports/hub * 2hubs/rpi => 8ports) :( – tarabyte – 2013-10-29T20:49:32.290

what USB hub are you using? – Phill Pafford – 2014-03-12T01:33:28.523

You should have no problem with 2x 10port hubs on a rasp-pi. I have tried a 49 port hub with full erupters and had several issues (using minepeon on the pi).

Also, I can easily run over 100 erupters using a single instance of BFGminer on a laptop with windows 7; I don't know how this would work on a rasp pi though.

I don't know about tools to get the numbers you are asking about, but hopefully some of this info will help a bit!

vnhyp0

Posted 2013-10-28T17:46:17.150

Reputation: 301

I have personally tried many erupters on a RPi. With 9 devices it was stable, with 21 devices it would have issues. After a couple days of random hangs, erupters stopping, and other nonsense I switched out the RPi for a netbook and haven't looked back.

ldm314

Posted 2013-10-28T17:46:17.150

Reputation: 1