Why when I use 2 GridSeed controlled by RaspBerry the hashrate become so slow?

[D4rkAng3l]

Hello to everybody,

I have the following situation that is going me crazy.

I have 2 GridSeed that I controll with a RaspBerry Pi (the GridSeed are connected to an USB HUB that is connect to my RaspBerry).

On the RaspBerry I use RaspBian and I have installed CPU miner.

To use both I use the screen linux command. So in the first screen I execute CPU miner for the firt GridSeed unit and in the second screen I execute CPU miner for my second unit.

It work...but the problem is that when I execute cpu miner for the second GridSeed unit the hashrate become very very slow (slower than the execution of a single gridseed, but both are working...I can see it in the program output).

Why? What could be the problem?