Power without PSU????? Weird!!

[otheos]

This is one heck of a weird thing.

Last night I decided to power down my main box. No problem it went down and I switched off the aux fans (external power).

After about an hour my wife powered up her box to see her emails and I soon noticed my HD cages leds were lit and the northgate fans spinning. My box that I had powered down earlier!

I thought I had left WOL and it powered up for some reason, but no, it was still off. So I started looking, switched off the rear PSU switch, removed the cable, removed the aux power cable (for the fans) and the leds were still on, and the northgate fans spinning.

What the heck? There was absolutely no source of power to the box!! Or so I thought.

I was just about to start pulling my hair out when my wife powered down her box and all of a sudden my box's leds and fans stopped!!

Ok, here's the explanation: My wife's box has an external firewire DVD-R. The enclosure has 3 firewire plugs, one is connected to my wifes box, the other to my box. This way both boxes can access the DVD-R and on top have 400Mbit tcp/ip networking

Now it appears power from my wife's firewire comes to the DVD-R (which is switched off!!) and then to my box. Weird!!!

I don't like the idea as god knows what else might be getting power. I mean really the two IDE HDD cage LEDs were on (the HDDs were not spinning though) and the northgate fans. And both are plugged to the PSU not the motherboard. So how is the power from the firewire card making it through the PSU and to the calbes to the various devices, and what else could be getting power from it that shouldn't?

Is it dangerous? is it random? and how on earth does it work?

[hawkeye177]

ROFLMAO

Sorry i can't help ya.

[otheos]

Indeed funny, I had to sit down and have a drink to figure out what it was happening.

I need somebody really knowledgable to advise me as I think it's really complicated (power coming from the firewire down the PCI bus up the PSU cable and through to the power calbes to the fans and HDD cages??

[jtzou]

What I'm curious about is TCP/IP w/ Firewire. Never seen it before but wondered if it was possible. :P

[otheos]

It is possible and very fast. It's in the ieee1394 whitepaper but only WinME and WinXP support it natively. For Win2k that my wife uses you need software (falsly called "emulation" as TCP/IP is native to firewire) that you have to pay for (and this is outrageous but we live on earth so...).

For my box, linux ieee1394 tcp/ip works fine (and free).

It's very fast and the idea of sharing a DVD-R and have networking is nice What I like most, is burning a dvd-rw from my box, from data from wife's box, coming all through the same cable Nice!

[Peter M]

Well since there are power lines on the FireWire cable (for host powered devices), it looks like the designers of your computer's internal FireWire card forgot a separation circuitry to avoid flowback of power back into the (self powered) computer.

Having that symptom can severely toast things, since practically everything is powered off one card's narrow power traces.

regards, Peter

[otheos]

Thank you Peter, I will keep the firewire cable off when the system is powered down, but what about when it's powered up? I would gather power is still coming in then.

Thanks again.