Standards specify an USB port should supply at least 500 mA. Dekstops usually give way more than that and thus these drives work perfectly on dekstops (never encountered one where my 5400 rpm external drive failed). However, due to power limitation and battery preservasion almost all laptop give axactly 500 mA/port. (Not 100 as this wouldn't even be enough o run my dual optical mouse). I have experimented a lot and found that 20-30 Gb 4200 rpm work on the power provided by the USB ports on the 8100 and 8600. I have tested it on many other notebooks of friends and all those failed. The hard drive came on and shutted down half way due to power failure. Seems like dell laptops give a good ammount of USB power compared to other notebooks.

There are two solutions to make larger or faster external drives work on the USB port without extrenal power adaptor :

1 - There are USB cables that connect to two USB ports. One is a standard USB cable and another is a pass through that just takes power from the USB port and allows another USB devices that doesn't require a lot of power (like a mouse) to be connected. This way the hard disk has 500 mA + whatever is left on the other port. This kind of cable works beautifully with my very power hungry toshiba GAX4019 5400 rpm drive and my dual optical mouse (who eats 150 mA). These cables are however very difficult to come by (mine was included with the external casing) Anyone who knows a place to get them freely, please post as I would like one for my second HDD casing.

2 - Using a small 5 V battery pack. This provides the HDD with enough power to work on an USB port. Some drives allow the battery pack to be disconnected once they have booted, other more power hungry drives like my 5400 rpm shut down when you do this and drain the battery packs pretty quickly. I dunno A place where to find such batterys. I took a 5 v GSM battery and connected a fitting power cord to it, worjs like a charm as well but is less good than the cable solution.

With the 2.5" enclosure I have (TT-954U2F) I can use it without external power source, Just the USB connection (single USB connection). Though I'm not sure if that allows enough power to boot from the external HDD. I simply use it to store or back up files from my internal HDD (doc's, MP3, photos). It does come with a PS/2 with a pass through that plugs into the unit for additional power (though my 8500 dosen't come with a PS/2). It also come with a Firewire connection.

It's a good enclosure, I recommend it.

Message Edited by RojasTKD on 01-23-2004 01:14 AM