Re: PCI cards or hub?

On Mon, 5 May 2008 00:30:01 +0100, wildrover.andy@xxxxxxxxxxxxxx (Andy
Hewitt) wrote:
Jaimie Vandenbergh <jaimie@xxxxxxxxxxxxxxxxxxxxx> wrote:
On Sun, 4 May 2008 17:29:20 +0100, wildrover.andy@xxxxxxxxxxxxxx (Andy
Hewitt) wrote:

I need to plug in at least 6 extra USB devices. One of these is my UPS,
which obviously needs USB power after a power failure, so needs to be
plugged into the Mac directly really.

Wait, what? The UPS will be running of its own battery, as will
(presumably) the Mac. It certainly won't be pulling power from the Mac
via USB.

No, it'll need power to the USB just for communications, otherwise the
Mac doesn't know it's on UPS power does it.

Yes, it will - it's not a dead-man-switch connection, the UPS actually
talks data to the computer. Battery life, mains status, depends on
what the UPS mfr makes available.

If I stick it through a hub
that has its own power, it'll lose comms when the power to the USB hub
fails (the hub isn't on a UPS powered socket), and thus the G5 won't
know to shutdown before the battery runs down.

(I would recommend putting the USB hub on a UPS-powered socket, since
it hardly draws any juice and at some point you'll discover that
you've got your mouse and/or keyboard through it, thanks to Murphy)

The best way to ensure this, is to connect the USB link for the UPS to a
USB port that will stay live when only the UPS is powering the system -
i.e. a built-in USB port on the G5.

That's definitely true, but for not for the reason you have in the
first para.

Cheers - Jaimie
--
"I have an asteroid named after me. Isaac Asimov's got one too.
It's smaller and more eccentric." -- Arthur C. Clarke
.

Relevant Pages

  • Re: House Power Failures and Mac
    ... the Mac with a USB Cable, and it goes right into the Energy Saver under ... and it sees the UPS I have. ... I let it sleep all night usually and it's here I'm worried about a power ... protect only power ports as well as power backup power ports. ...
    (comp.sys.mac.apps)
  • Re: PCI cards or hub?
    ... It certainly won't be pulling power from the Mac ... No, it'll need power to the USB just for communications, otherwise the ... Mac doesn't know it's on UPS power does it. ...
    (uk.comp.sys.mac)
  • Re: Can PCs turn on/off their remote PCs?
    ... (at 120 volts) ... stuff enough inside of a Mac Pro to pull that kind of power. ... Turn on/off regulated 240 volt power to any selected outlet, ... Turn off/on raw unregulated power to the input of the UPS. ...
    (comp.sys.mac.advocacy)
  • Re: Recommendations for UPS for Mac OS X / Server
    ... I've decided it's time to bite the bullet and upgrade my UPS (when the ... power went out a couple of weeks ago I discovered the battery only had ... The USB ones apparently work well directly in OSX, ... scheduled battery test routines as well. ...
    (uk.comp.sys.mac)
  • Re: Kernel 2.6.19.2: Belkin UPS on Serial vs. USB
    ... on battery power: ... seconds) after disconnecting the UPS. ... so I chose to use USB. ... I think this is a userspace issue, as it's a userspace program that is ...
    (Linux-Kernel)
Loading