External HDD that's USB powered

Dell dimension 3100 / DV051
December 13, 2008 at 06:52:55
Specs: Windows XP Home Edit, Intel Pentium 4 CPU
I want to buy an external HDD but don't know whether to get one that's USB powered only or one that also includes a separate power supply. I read that a separate power supply would be a more powerful choice, making the hard drive run faster. On the other hand, I was told that the USB port can damage over time when using a USB powered external HDD. Should I buy an external HDD that also contains a separate power supply or is it ok to buy say a pocket HDD that powers straight from the USB port?


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December 13, 2008 at 07:17:54
Hello, I use one every day at work, (WD) that is USB powered. I have had this drive for 1 1/2 years with no concern. When using the drive I plug it in and it remains stationary throughout the day. I personally beleive that moving the drive when it is hooked up is what causes the most damage to the drive and the attaching cord. When shutting down for the evening I always allow the hard drive to "spool down" before moving it.

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December 13, 2008 at 07:23:14
I noticed that pocket / portable HDDs have a 5400 RPM (Revolutions Per Minute) and the external HDDs with separate power supply have 7200 RPM. Is this a big factor in choosing? Will my computer run much faster with a 7200 RPM rather than a 5400 RPM?


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December 13, 2008 at 07:45:21
The biggest factor would be the USB port on your PC. Older PC's and laptops, have USB 1st generation, newer PC's have USB 2nd generation ( much faster ). All of the hard drives offered today are USB 2, they are backwards compatable with USB 1, but will operate slower. The transfer rate would be slightly faster with the 7400 rpm HD, but unless your transfering large files the difference would be unnoticeable.

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Related Solutions

December 13, 2008 at 07:53:42

The rotational speed isn't a factor with USB drives because the bottleneck is the USB connection, not the drive transfer spped.

IMO 2.5" USB only units were originally designed to be portable. They do NOT perform as well as a 3.5" enclosure with an AC power supply.

All 3.5" enclosures are not created equal. Heat is the enemy of these devices. 2.5" USB drives rely strictly on passive cooling. The more expensive ones use an aluminium case to disapate the heat. Even those get hot because they are designed for intermittent use and folks have them running constantly.

I recommend a large External enclosure with a cooling fan included. The 3.5" drives are the same drives that are used internally. Ther is nothing wrong with using a 5400RPM drive as a backup drive, even internally.

Now, for the 64 dollar question. Why do you want an external drive? Do you use a laptop? Is your computer old and therefore size limited?

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December 13, 2008 at 12:02:43
I've never come across a USB connected external hard drive that does not require TWO power sources.
A single USB connection alone, which provides up to and including a standard 500ma max at 5v dc, probably cannot provide enough current for both the hard drive and the circuits in the external box.

Some mboards automatically generate a warning or overload message if you try ro draw more than 500ma from a USB port.

Either you get an external drive that also has an external power adapter connected to the external box (common for ones with 3.5" desktop sized drives), or you get one that has cables with TWO USB connections at the computer end, one cable only needs to have two wires for 5v power, or you can connect the one cable that requires only 2 wires to a power adapter meant to be used for providing 5v to a USB device, such as one for a MP3 player (common for ones with 2.5" notebook sized drives).

The hard drive alone can require far more than 500ma.

I have an IDE 80gb 3.5" drive that requires .72 amps (720ma) at 5v and .52 amps (520ma) at 12v, which is typical.
(even if the box without an external power adapter converted 5v to 12v 100% efficiently, which is impossible, the drive alone would require 1.968 amps at 5v)

I have a SATA 80gb 2.5" drive that requires .48 amps (480ma) at 5v - the circuits in the external box would have to draw 20ma or less, which is very unlikely.

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December 13, 2008 at 18:33:15

I want an external HDD because my computer is running slow due to the storage capacity being almost full. I have an 80GB Dell Dimension 3100. Plus, I want to start storing a lot of DVD movies and photos. I want to buy a 320GB - 1TB external HDD but can't decide on a pocket/passport HDD (USB powered) or the slightly bigger dimension external HDD with power supply.


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December 13, 2008 at 18:46:42

Does a higher RPM (Revolutions Per Minute) make my computer run faster like having more RAM? If I bought a 7200rpm over a 5400rpm, will there be much of a difference when actually using the computer. Sometimes my pc runs slow e.g. when I click on the 'start' button and then 'all programs', the icons might take a while to appear. Or if I click on 'my documents', there is an image of a torch that moves until the 'my documents' opens. Will a higher RPM show a difference in pc performance?


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December 13, 2008 at 18:51:34
So right now you have no backups and intend to store lots more stuff without any backups?

I suggest you install an internal drive as well as buying the external. If your computer can't accept a large drive, which is likely, you can add a controller card to allow any size drive.

If you don't I can almost guarantee you will be back here in the future asking for help with recovery.

If you want suggestions post back.

After looking up your computer I think you can install any size hard drive in there now.

I don't know any suppliers in Australia, if that is where you live.

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December 13, 2008 at 19:48:35

Yes, I live in Australia. I didn't know that a computer can have a limit on a hard drive's capacity. Say I bought a 1TB HDD and my PC doesn't accept this large drive, must I buy a controller card? What is a controller card and how much do they cost?


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December 13, 2008 at 19:57:06
Your answer is yes, however as I read about your situation it sounds more like the existing drive is full and has little virtual memory remaining, that in itself will slow it down. Another area that does not get enough attention is the registry, it probably has alot of old unused entries that will slow down the fastest PC's, but that is a whole other topic. Does your PC have the max. amount of memory (ram) installed? If not that will speed it up more than the hard drive speed alone. You also mentioned that you were planning on storing DVD's on the external drive, that being said tells me that you should buy the largest hard drive that you can afford, as DVD's take up alot of space unless they are zipped (compressed), here again more time to zip and unzip large files. Hope this helps.

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December 13, 2008 at 20:24:59

I don't know how we can tell you if more RAM would help if we don't know how much you currently have.

If you install a 7200RPM drive internally it may have a slightly faster response time. The amount of cache is more important IMO.

I checked the Dell site and your computer came with an optional 250 GB SATA II hard drive. That means you will have no problem installing any hard drive size. You will need a SATA data cable and mounting screws in addition to the SATA II drive.

The link below are for SATA II hard drives. Newegg.com does not ship to Australia so this is for reference. Prices are US dollars.

You won't need a controller card.

I applied filters to show only SATA II drives and nothing smaller than 160GB. I showed only TWO brands that I recommend.

You can also buy a USB external enclosure and drive separately. That way you get the brand you want.

If you are interested in buying any of these items I suggest you start a new thread in the hardware section asking for recommended online or brick and mortar vendors in Australia.


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December 13, 2008 at 20:53:18
Mech1993 & OtheHill

Thank you so much for your help!!!


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December 13, 2008 at 23:05:37
"Does a higher RPM (Revolutions Per Minute) make my computer run faster like having more RAM? If I bought a 7200rpm over a 5400rpm, will there be much of a difference when actually using the computer."

Adding more ram doesn't make Windows run faster unless the amount you already have installed isn't adequate for the programs you use.
E.g. for XP 256mb is just barely enough for Windows to run at the speed it should, if you're not using integrated video. Many people get by fine with 512mb for most programs. Only demanding programs most people don't use, or high end games, might need more ram.
Ultimate Memory Guide
How Much Memory Do You Need? etc.

The difference between a drive that runs at 5400 rpm in comparison to one that runs at 7200 rpm is mostly the average seek time is proportionately faster on the faster drive (1.33 X in theory), but it's only a difference of milliseconds (thousandths of a second) at best.
The size of the buffer cache on the drive, and the maximum data burst speed the drive can achieve, is more important - e.g. up to 133mb/sec for an IDE drive, 150mb/sec for a SATA drive, or 300 mb/sec for a SATA-II drive.
If the buffer cache size and the max burst speed is the same, you will be hard pressed to notice much difference.

Freeing up space on your too full partition Windows boots from, usually C, definately makes a noticable difference in Windows performance.

Using a video card in a slot rather than integrated video allows your ram to use it's maximum bandwidth - sharing the ram with the video often halves it - and that makes a noticable difference, even with the same amount of ram, especially when your system is being more heavily taxed.

However - your mboard (see the specs below) has no PCI-E X16 slot for a PCI-E video card - it has just two PCI slots, and a PCI-E X1 slot.
You would need a recent chipset PCI video card, or a PCI-E X1 video card if they exist, for the video to be better than the onboard video.

Also, your power supply has only a 230 watt capacity (see the specs below). If you think you may add a PCI video card, check the specs of the particular card on the manufacturer's web site to see what minimum required power supply capacity is, and possibly the minumum amperage it must supply - you may need to get a better power supply as well.

I found the specs for a Dimension 3100 in Australia that has a 3ghz Pentium 4 cpu, Windows XP Media Center Edition 2005, a 160gb hard drive, and 512mb of DDR2-533 ram, but the configurations probably vary.

Make sure you back up your system, and make the Rescue Disk set you're supposed to make, with a program already put there by Dell in your Programs list somewhere, while Windows is still working so you can re-install your original Dell software including Windows if you need to.
If you have Windows XP Media Center Edition 2005, you will need the 2 disk OEM MCE set to load Windows MCE otherwise.

Technical Support for Dimension 3100/E310

System Configuration - enter your service tag to find your exact configuration.

Manuals, English

Service manual, HTML (PDF also available)

Specs, for the series:

Those appear to be identical to those found on the USA Dell site.

As OtheHill has already surmised, those specs confirm you can install any size of current hard drive.

If I were you I would install one internally - inside the case - rather than bothering with an external one at all, unless you have a specific reason you want it to be portable.

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