So I whip out a FTDI-based multiport Serial USB Adapter.... [SB QUAR: Tue Feb 5 10:15:47 2013]

[Karl Denninger]

On 2/5/2013 10:44 AM, CeDeROM wrote:
> On Tue, Feb 5, 2013 at 5:27 PM,  <chrish at ultimatedns.net> wrote:
>> Understood. I was referring to the _computers_ power supply. :)
> Still it may be caused by some issued on the USB bus power management.
> Normally an USB port can supply 500mA of current. Above that port
> should be disabled by the host if I remember correctly. If there is a
> hub inside the serial port adapter it would be good to know it it is
> powered directly from the USB port or does it have its own power
> supply...
>
> There could be too much power drain from the USB port by external
> devices attached to the hub/adapter. But this would be rather obvious.
>
> There may be some misunderstanding between USB Host and the self
> powered USB device, so they cannot agree on the power supply level,
> which seems more probable :-)
The FTDI adapter has the provision for an external power supply (+5V)
but it does not require it unless you're running off an unpowered bus,
which is not normally the case.  500ma is quite a bit of available energy.

I suspect the issue is found in the KVM, which attaches as a "low" speed
device; I'm going to see if I have the same issue with other USB devices
connected while the KVM is on the box.

-- 
-- Karl Denninger
/The Market Ticker ®/ <http://market-ticker.org>
Cuda Systems LLC