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how many amps in MBP USB ports?

Z

ZballZ

macrumors regular
Original poster
Nov 11, 2006
246
0
So, I am buying a external harddrive for my mac. Found a nice Western Digital model, the Passport. Comes in various colours, I'm getting a 250 GB.

Only thing is, there seems to be some issues since it is using power from the USB-port. I found a zillion posts online about this, some people say it is not a problem, others say that mac-usb-ports simply does not deliver enough amps, for the drive to function. Well, no problem, WD has a special Y-cable, connecting to TWO usb ports. Only thing is, there is only one usb port on each side of the mac, so the cable wont reach both ports anyway :eek:

The weird thing is, that the drive comes with different SPECs, when the color is different. The specs for THE RED version 250 GB, says it requires 650 milliamps to function - the black 250 GB requires 1000 milliamps. Seems very strange to me, since i figure it must be the same drive inside the casing.

Well, long story short - is there anyway to find out how many amps a MBP 15" delivers? Just wanna make sure before I order the drive. (and yes, I know, why dont I just get one with a power supply - well, too lazy to drag too much stuff around)

And, anyone in here that has the drive and knows if it runs or not? (I dont trust people outside this forum :) )

THX
ZballZ
 
Over here where I live, the black one is cheaper than the red one. Maybe the red one really draws less power and the extra cost is the premium for this? :confused:
 
tanjacob said:
Over here where I live, the black one is cheaper than the red one. Maybe the red one really draws less power and the extra cost is the premium for this? :confused:
Click to expand...

They seem to switch off week to week. I got a white one for cheap, then the next week, the black one was cheap. And we're talking a price difference of $70 just for the different colors!

I can't run mine from the left usb port i believe. I'm not sure if i'm still having issues. I'm just used to it by now I guess.:eek:
 
Could be. Other reason could be that BLACK was the original product, when they started doing the colours (RED, GREEN, PINK) it was only as a limited (thus more expensive) edition. For some reason, it doesnt seem like a limited edition anymore, cuz they keep producing them...

...and here (denmark) the price is pretty equal - only about 10-15$ difference, could just be the more expensive cover...
 
I have a 7K200 200Gb running in an Akasa Integral P2 eSATA enclosure.

It works perfectly over eSATA :)

Gets the full 60+ MB/s and seek times are all correct :)

7,200 RPM disks use the most current so yours will be fine.
 
I'd assume it would work (those Y cables are pointless anyways)

On the other hand the net data rate you'll get over USB will be well below of what a 5400 rpm disk can supply, so I wouldn't pick a 7200 model (or use eSATA like Concorde Rules does)
 
dont get it, nerdbert. If concord rules gets the full eSATA potential, running his 7200 disc on usb-power, why should a smaller drive, like 5400, get lower seek times when running on the same amount of mA?? (obviously slower cuz its a slower drive, but I mean relatively and power-related...)

And - if youre right - do you have any idea how much slower a 5400 would be running of the USB-power?

The seek times on the WD Passport seems pretty good - and since it doesnt even have a regular power supply, I guess the benchmarks comes from testing it running on the usb-power...
 
ZballZ said:
dont get it, nerdbert. If concord rules gets the full eSATA potential, running his 7200 disc on usb-power, why should a smaller drive, like 5400, get lower seek times when running on the same amount of mA?? (obviously slower cuz its a slower drive, but I mean relatively and power-related...)
Click to expand...

I think I didn't get it. I was under the impression that you wanted to not only power but also connect the hard-drive via USB. In that case a 7200 wouldn't make sense.

I wasn't aware that there are eSATA solutions which use the USB port for power supply. Sorry for the distraction.
 
No, youre absolutely right. I do want a drive that connects with only one usb-cable. So, youre saying that running both data and power thru that single cable will reduce the speed of the drive?

If i understand Concord Rules' setup correctly (i did check out that drive he mentions) he runs the data thru the esata, and power the drive by USB - and gets full speed this way. (although i dont get how he gets 60 MB/S on a 7200 drive, running only on 500 mA from the USB - when you argue that the 500 mA can barely power the 5400 drive...)
 
It's not a power issue, but related to the net data rate you can archive over USB, which is around 30 Mb/s*

So the speedup you'll get from running a 7200 drive instead of a 5400 will be zero over USB, because 5400 drives are already faster than 30 Mb/s. The only difference you'll notice is the price.

If speed is important to you and you definitely want a 7200 drive I'd recommend a Firewire solution. You get 1,5 A over a 6-pin FW connector and don't have to mess with more than one cable. However, FW400 might be too slow for a 7200 drive - I don't have any numbers right now. I only remember that FW400 is faster than USB 2.0, even though the nominal rate is lower (400 Mbit vs 480 Mbit)


* Might be 35 Mb or just 25 Mb - it really depends on the SATA to USB bridge the device is using...

edit: Or you buy a eSATA card and use two cables. eSATA provides the best data rates right now. I wouldn't do that, but if speed is of high importance...
 
THX! Now I got it - I was all focussing on the power-thing...

USB will be fine then - i already have a 7200 external USB-2 drive - as long as it is a fast as this, it will do it for me. And as you're saying that the limitation is not the power, not the drive - but the USB - I guess it will be pretty much the same speed as my old one... Thx again...
 
ZballZ said:
And as you're saying that the limitation is not the power, not the drive - but the USB
Click to expand...

Sorry I have to clarify again: Those drives still suck more power when spinning up than the USB standard provides. But that doesn't mean the MBP's port can't deliver it. I guess it will be fine based on my experience with this issue and Concorde Rules has no problems with a 7200 powered by USB.
Just give it a try. The worst thing that could happen is that the computer powers off (and can be restarted after unplugging). Just send it back and buy a FW400 case for the hdd in case it doesn't work out...

ZballZ said:
Thx again...
Click to expand...

You're welcome :)
 
Yes, I use the USB connector to power it and eSATA to get proper transfer rates.

I flick the switch at the back and I can power + data over USB using a different cable.

I only got a 7K200 is because in a 130Gb lightroom library a quick seeking drive is whats needed.

5400 RPM drives have a slower seek time (the ms rating) and usually slower transfer rates but the 320Gb WD is quite close but slower in seeking.

Need 4GB RAM next to complete the transition.

I bought the 7K200 200Gb, eSATA enclosure and eSATA card for £150 ($300ish US).

Fastest external hard disk solution by far (A 64Gb SSD will be QUICK).

But whatever you do, it should be fine, unless there is some strange reason the WD uses more power :/

My next upgrade is a 250Gb 7200 RPM drive :)
 
Not enough amps to kill you, but enough to power most things. I wouldn't count on the Battery in the MB for long though.
 
The 250gb passport drive works perfectly with my MBP! If you live in Copenhagen and want to see for yourself, PM me :)

The eSata-USB solution sure seems like a sweet one for a quick on-the-go drive :p
 
PimpDaddy said:
The 250gb passport drive works perfectly with my MBP! If you live in Copenhagen and want to see for yourself, PM me :)

The eSata-USB solution sure seems like a sweet one for a quick on-the-go drive :p
Click to expand...

Yes - im in copenhagen. But i'll take your word for it :)
 
Papajohn56 said:
Not true. That's the minimum it must be, the MBA has one rated at much higher, so it can support the Superdrive
Click to expand...

500 mA is the maximum power output the USB standard allows. Of course nobody is preventing Apple from deliberately designing ports which can supply more. But at least on apple.com they seem to carefully avoid to call the MBA Superdrive a USB device - they use terms like "usb based" or "connects ... with a single USB cable"
 
I use a 160GB Iomega portable drive powered off USB and it works fine without any problems.

There is two USB cables I got with the drive, meaning you could power the device off another computer or USB socket and attach the other USB cable to the laptop.

Handy, but I ended up cutting off the spare USB cable for power supply, I never use it, never will and it just clogged up my desk space and laptop bag.
 
I've read the reviews of people who have issues with this drive and they all seem to be using USB 1.1 which doesn't deliver as much power as USB 2.0.
 
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