PCI cards or hub?
in [UK Mac]
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From: Andy Hewitt on 5 May 2008 06:13 Jaimie Vandenbergh <jaimie(a)sometimes.sessile.org> wrote: > >> 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. So if I don't plug in the USB cable, my Mac will still know it's connected to a UPS? > > 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) Hmm, good point. > >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. I still don't see why not? -- Andy Hewitt <http://web.mac.com/andrewhewitt1/>
From: Andy Hewitt on 5 May 2008 07:11 Jaimie Vandenbergh <jaimie(a)sometimes.sessile.org> wrote: [..] > >So if I don't plug in the USB cable, my Mac will still know it's > >connected to a UPS? > > Let's start again... > > You have a UPS. You plug the Mac into the UPS power outlet. The Mac is > now protected from short-term mains outages. Yup. > You also connect the USB cable from the UPS to the Mac. The USB cable > allows the UPS to inform the Mac when the power is out, by sending a > data packet that the Mac is listening for. It also allows the Mac to > ask the UPS how much battery is available, and so on. This can be a > direct cable, or indirect through a hub. > > The mains power goes out. Yup. > If a hub was in use, and it was not powered from the UPS, the Mac will > now no longer be able to monitor/recieve info from the UPS - this > would generally be non-optimal but not fatal. So far. > If the USB comms between UPS and Mac are still in place, the UPS sends > a packet over USB to the Mac saying "I've switched to battery mode". > The Mac then does whatever comes naturally - usually this would be to > not worry until the UPS reports less than 10% battery left, at which > point to shut down. Right. So if the USB has lost communication, how does the Mac know that there's only X% of battery left, or that it's been running on UPS for X-minutes? I guess this might depend on the hub, and whether it'll transmit data without being powered. I don't think the one I have does so. > So at no point does the UPS require 5V@.5A from the Mac's USB cable to > function. Only the data transfer wires are used. > > I suppose the UPS *could* attempt to monitor when the Mac has powered > down by watching the USB 5V wire, but I've never seen one that did - > and the UPS doesn't care anyway. It wouldn't be reliable either, since > most mains-powered computers hold 5V on the USB power wire even when > they're nominally powered off. Erm, yes, actually I know the UPS doesn't care what's happening, it the Mac I'm interested in. How does it know what's going on if the USB link is dropped? Obviously it might know the power was restored if peripherals regained connection. -- Andy Hewitt <http://web.mac.com/andrewhewitt1/>
From: Graham J on 5 May 2008 07:38 "Andy Hewitt" <wildrover.andy(a)googlemail.com> wrote in message news:1igguvm.1yn6zjvy4q6sdN%wildrover.andy(a)googlemail.com... > Jaimie Vandenbergh <jaimie(a)sometimes.sessile.org> wrote: > > [..] >> >So if I don't plug in the USB cable, my Mac will still know it's >> >connected to a UPS? >> >> Let's start again... >> >> You have a UPS. You plug the Mac into the UPS power outlet. The Mac is >> now protected from short-term mains outages. > > Yup. > >> You also connect the USB cable from the UPS to the Mac. The USB cable >> allows the UPS to inform the Mac when the power is out, by sending a >> data packet that the Mac is listening for. It also allows the Mac to >> ask the UPS how much battery is available, and so on. This can be a >> direct cable, or indirect through a hub. >> >> The mains power goes out. > > Yup. > >> If a hub was in use, and it was not powered from the UPS, the Mac will >> now no longer be able to monitor/recieve info from the UPS - this >> would generally be non-optimal but not fatal. > > So far. > >> If the USB comms between UPS and Mac are still in place, the UPS sends >> a packet over USB to the Mac saying "I've switched to battery mode". >> The Mac then does whatever comes naturally - usually this would be to >> not worry until the UPS reports less than 10% battery left, at which >> point to shut down. > > Right. So if the USB has lost communication, how does the Mac know that > there's only X% of battery left, or that it's been running on UPS for > X-minutes? IT DOESN'T !! IT DOESN'T !! IT DOESN'T !! IT DOESN'T !! Hence the need to maintain the communication between the UPS and the Mac. Either power the USB hub from the UPS or connect the UPS signal cable DIRECT to a USB port on the Mac. -- Graham J
From: Andy Hewitt on 5 May 2008 08:18 Graham J <graham(a)nospam.zen.co.uk> wrote: > IT DOESN'T !! > IT DOESN'T !! > IT DOESN'T !! > IT DOESN'T !! > > Hence the need to maintain the communication between the UPS and the Mac. > Either power the USB hub from the UPS or connect the UPS signal cable DIRECT > to a USB port on the Mac. Yes, that's how I was understanding it. -- Andy Hewitt <http://web.mac.com/andrewhewitt1/>
From: Jaimie Vandenbergh on 5 May 2008 09:00
On Mon, 5 May 2008 13:18:13 +0100, wildrover.andy(a)googlemail.com (Andy Hewitt) wrote: >Graham J <graham(a)nospam.zen.co.uk> wrote: > >> IT DOESN'T !! >> IT DOESN'T !! >> IT DOESN'T !! >> IT DOESN'T !! >> >> Hence the need to maintain the communication between the UPS and the Mac. >> Either power the USB hub from the UPS or connect the UPS signal cable DIRECT >> to a USB port on the Mac. > >Yes, that's how I was understanding it. Jolly good, then all is well. Cheers - Jaimie -- My swerver room, my patch panels. By the time they figure out why none of the ports on their floor box work anymore I'll be done, dusted and down the pub with a pint of something brewed with yeast that was smarter than they are. -- Matt S Trout, asr |