I have an old G-Tech Mini portable hard drive (FW800, bus-powered) that I don't need any more, so as an experiment I took the actual hard drive out and replaced it with a 512GB Crucial M4 SSD. I would like to use it as an external boot drive over FireWire 800 to speed up an old 2007 iMac.

So far, it seems to be running great! The drive shows up and is nice and fast. But I'm worried that this isn't a 'proper' hard drive enclosure - it could be that it was only designed to work with its original hard drive. I have no idea whether the SSD takes more or less power than the original drive. There is a very slight whining sound when the drive operates, but I can't remember if that was always there. The G-Tech drive was a model from about 5 years ago.

I know that with FW800 and without TRIM I won't be getting the best performance out of the drive, but I'm not worried about that. I just need to know that the chassis won't do any physical damage by delivering the wrong voltage or whatever. Am I doing any harm to the drive and/or enclosure?

2 Answers 2


The SSD draws a lot less juice from your power supply and doesn't produce as much heat as a spinning hard drive. You could say your enclosure is quite over-engineered for your SSD.

I would be concerned if you'd try the opposite (putting a spinning harddrive into a SSD enclosure).

That being said it would be better if you'd put the SSD directly into your iMac. Or swap the drives. It's not that difficult and you'll probably gain quite some speed.

  • I know that an SSD's average power draw is less, but I've had problems before with an enclosure because some SSDs have much greater momentary power draw, even though the average is lower. Could that affect things?
    – Ric Levy
    Nov 29, 2015 at 15:59
  • I'd find it hard to believe that silicon can draw more power than any harddrive engine. As somebody noted in another answer, Firewire can deliver up to 45 watts. The power adaptor for a Macbook Air is 45 watts and can charge the battery while you're using it. I admitted that - merely because of the battery presence - that doesn't proof anything about momentary power capabilities, it does put things in perspective. Bottom line, I rather think you just enlongered the predictive lifespan of your enclosure by putting in the SSD.
    – EDP
    Nov 30, 2015 at 9:26
  • The issue I experienced before was using a USB 3 enclosure through a converter to a thunderbolt port. A large capacity SSD wouldn't work properly, and after some investigation I discovered that the SSD had moments of brief power draw that were too much for Thunderbolt 1. I know that this was not an issue for USB 2/3, so I assume it's not an issue for FireWire 800 either. Thanks for your help!
    – Ric Levy
    Nov 30, 2015 at 14:12
  • One could say that on level of juice availability Thunderbolt was a step down from Firewire. If I'm not mistaken Thunderbolt has a max of 10W which is far less than the (theoretical) 45W for Firewire. Most Thunderbolt devices and definitely the hubs have external power supplies mainly because of that. The new Thunderbolt 3 is spec'ed just a tiny bit higher at a theoretical max draw of 15W.
    – EDP
    Nov 30, 2015 at 17:51

FireWire specifies a 30 volt and 1.5 amp bus (45 watts?! Holy Christmas!). In any case it appears the FireWire port has plenty of power for your drive, and Apple always was a fan of target disk and FireWire.

It does sort of beg the question as to why you're choosing to boot it externally and not mount it internally where you could get even better speeds from the SATA port, but all appears to be kosher.

  • Thanks, but I'm not really worried about the FireWire port itself - I'm worried about the actual enclosure. It was sold as a sealed portable hard drive, but I've taken it apart and put a different drive (the SSD) inside. Since it was never intended to have the drive swapped out, I want to make sure I'm not doing any harm.
    – Ric Levy
    Nov 29, 2015 at 7:34

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .