Power HD only with Firewire. Why no one doing it?

Posted:
in Current Mac Hardware edited January 2014
Firewire provide 45w, more then enough for 3.5" External HD. Yet i haven't seen any EHD that can do that yet. Why is that?

Comments

  • Reply 1 of 11
    royboyroyboy Posts: 458member
    Quote:
    Originally Posted by ksec View Post


    Firewire provide 45w, more then enough for 3.5" External HD. Yet i haven't seen any EHD that can do that yet. Why is that?



    Not sure I totally understand the question, but let me ask you a question about your question.



    Are you indicating that Firewire provides for 45 watts of power and that an external hard drive could be powered by Firewire and that the external drive would need no external power source?
  • Reply 2 of 11
    MarvinMarvin Posts: 15,273moderator
    You mean like the bus powered firewire mobile drives Lacie sell?:



    http://www.lacie.com/products/product.htm?pid=10819
  • Reply 3 of 11
    leonardleonard Posts: 528member
    I have LaCie's PocketDrive which also works off of the Firewire power, and it works great. It does come with a power adapter, but you don't have to use it. I use to use it for my Ibook, but now I use it as an emergency HD to boot off of.
  • Reply 4 of 11
    aquaticaquatic Posts: 5,602member
    That's a great question. I find the power brick for my drive a pain in the ass. Plus, it would be nice to use it when I'm on battery away from an outlet. I suppose sometime this year I may buy a FireWire-powered mobile hard drive. Still, it is odd there aren't more out there that just use FireWire's power.
  • Reply 5 of 11
    zandroszandros Posts: 537member
    I guess it's to make sure you don't toast anything when plugging in and unplugging peripherals.
  • Reply 6 of 11
    mrtotesmrtotes Posts: 760member
    Quote:
    Originally Posted by Marvin View Post


    You mean like the bus powered firewire mobile drives Lacie sell?:



    http://www.lacie.com/products/product.htm?pid=10819



    Well, Yes there are plenty of 2.5" bus-powered drives but the OP is asking about 3.5" (high-capacity/high speed) drives.
  • Reply 7 of 11
    MarvinMarvin Posts: 15,273moderator
    Quote:
    Originally Posted by mrtotes View Post


    Well, Yes there are plenty of 2.5" bus-powered drives but the OP is asking about 3.5" (high-capacity/high speed) drives.



    They are both 7200 rpm but for higher capacity and lower price, it might make sense to have 3.5 inch drives. I guess why they don't is simply because they are heavier and so less portable. Also, bus powered drives are more dangerous to use as they can blow your motherboard and you can damage the drive by unplugging it as that also powers down the device.
  • Reply 8 of 11
    jeffdmjeffdm Posts: 12,951member
    Quote:
    Originally Posted by ksec View Post


    Firewire provide 45w, more then enough for 3.5" External HD. Yet i haven't seen any EHD that can do that yet. Why is that?



    Where did you get that 45W figure? I'm pretty sure it is wrong, that's about as much as a notebook computer takes, add 45W and the battery would overheat or at least go twice as quickly.. I think it's more like 15W, and that's the real problem because a 3.5" drive can easily take 10W and that doesn't leave much for power conversion and the interface circuitry.



    Wiebetech had one, but it was discontinued:



    http://www.wiebetech.com/products/ultragbplus.php



    I think it was pretty expensive. They never sold the bare enclosure, but I think the enclosure worked to add over $200 to the cost of just a bare drive.



    Quote:
    Originally Posted by Marvin View Post


    You mean like the bus powered firewire mobile drives Lacie sell?:



    http://www.lacie.com/products/product.htm?pid=10819



    That's a 2.5" drive. Bus powered 2.5" external drives are common.
  • Reply 9 of 11
    pyr3pyr3 Posts: 946member
    Quote:
    Originally Posted by JeffDM View Post


    Where did you get that 45W figure? I'm pretty sure it is wrong, that's about as much as a notebook computer takes, add 45W and the battery would overheat or at least go twice as quickly.. I think it's more like 15W, and that's the real problem because a 3.5" drive can easily take 10W and that doesn't leave much for power conversion and the interface circuitry.



    IIRC, USB2.0 provides .5A in the spec and Firewire provides for 1.5A. And IIRC, most 100GB 2.5" hard drives (at the time that I was looking this up -- last summer) need a max of 1A. This is mostly used to spin up the drive from a dead stop. It takes less power to keep it going and work the heads to read and write.



    I've heard the some USB2.0 buses provide more power because they are tapped directly into some motherboard bus (or power source) but this is more of a case that the motherboard designers were too lazy to regulated the USB2.0 bus power. Supposedly you can shorten the life of your motherboard or risk damage to the computer by drawing too much power over the USB2.0 bus like that. And in any case, it's not a reliable metric to design against.
  • Reply 10 of 11
    i've been using bus-powered firewire drives for years and year. great stuff. just plug and go.
  • Reply 11 of 11
    mmmpiemmmpie Posts: 628member
    I cant find an easy spec, but the bottom line for 1394 power is pretty low ( i.Link provides no power ). Macs supply 18v on the firewire bus, I think that they can do a reasonable job of powering a 3.5" drive. But PCs dont have 18v power supplies, and it is likely that the best you will get out a firewire port in one is 12v. I would hazard a guess that the lack of standardisation makes it too much work, and that it is cheaper to include a chinese wall-wart instead.
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