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gto47 · Apr 20, 2006, 09:57 PM

After the logic board failed on my G5, i picked up one of these new intel macs in the 20" variety. Since all of my data was on the two sata drives inside i bought two external enclosures so that i could continue using the drives. Sounds simple enough right? I went with the coolmax 3.5" enclusure which uses the prolific chipset. Its worth mentioning that prolific seems to be the only manufacturer of sata to firewire chips (most are usb2 only). Anyway if i plug in one drive it runs just fine. When I plug in the second both drives bounce and i get a device removal notice. Now i'm not doing anything special here, both are plugged directly into the two firewire ports on the back. What i think is that either a) the "8 watts shared" specification for the imac firewire is not enough or b) the integrated firewire bus in truth only 1 bus which is in some way inadequate for running the two drives. Both enclosures are powered of course. I'm pretty stumped. - I'm considering trying a powered firewire hub to see if that solves the problem.

mduell · Apr 20, 2006, 10:22 PM

3.5" drives idle between 5W and 9W, and draw a bit more than that on startup, so I'd guess it's the 8W shared limit; a powered hub may solve the problem.

Will C · Apr 21, 2006, 04:10 AM

Surely if external drives are powered (with external power supplies) then there should be no power drawn from the firewire ports of your iMac? or are you saying that both your drives are self powered?

mduell · Apr 21, 2006, 03:18 PM

Originally Posted by gto47

Both enclosures are powered of course.

I swear that said "Both enclosures are bus powered of course" last time I read it.

D'oh!

gto47 · Apr 26, 2006, 06:30 PM

I'm now on my second iMac, returned the first to the apple store because a) they didn't give me the 256vram on the first one & b)the first one had a slight screen defect. This new one still has the problem. I'm waiting on a hub, i'll let you guys know if that fixes anything. Just FYI the firewire seems to be about 4x the speed of the usb on these enclosures and the USB2.0 is a serious drag on the system during drive to drive file transfers.

gto47 · May 17, 2006, 04:56 PM

Still having problems after purchasing a powered hub. Hopefully others will let apple know of the problem as well. The usb interface seems to cause the finder to halt under heavy xfers. Waiting for a fix!

ghporter · May 17, 2006, 05:42 PM

One thing that USB beats firewire on hands down is device power management. A USB device must ask permission to power up, and if the controller doesn't have (or thinks it doesn't have) enough juice, it says "No." Firewire is not at all like that: you can plug enough stuff into a bus to pull it down into the dirt and will NOT get a notice that is what is happening. If both of your SATA enclosures are separately powered, this shouldn't be an issue, but obviously SOMETHING weird is going on.

SATA is supposed to be completely transparent, allowing you to simply plug and play without jumpers and the like. But how good is the controller at figuring out what's what? Have you tried plugging the two drives in differently? Different order, different port? They're fully powered on when you plug them in, right?

gto47 · May 18, 2006, 04:04 PM

Now it seems like its an issue with the drive enclosure. It doesn't seem like any mac can mount both drives simultaneously, hub or no hub. I still don't get it.

wowok1234 · May 19, 2006, 05:51 PM

The problem is that each firewire device has a unique ID, the GUID. This GUID is supposed to be different for all devices, but Prolific for some reason assigned the same GUID for some of their chips. When devices with same GUIDs are plugged into the same computer, the computer gets confused.

The Firewire section in system profiler will tell you the GUIDs for each device.

ghporter · May 19, 2006, 05:57 PM

Originally Posted by wowok1234

The problem is that each firewire device has a unique ID, the GUID. This GUID is supposed to be different for all devices, but Prolific for some reason assigned the same GUID for some of their chips. When devices with same GUIDs are plugged into the same computer, the computer gets confused.

The Firewire section in system profiler will tell you the GUIDs for each device.

Holy "Violate the whole standard," Batman! That's a really stupid thing for Prolific to have done-it BEGS for this sort of problem to occur. Or they never expected anyone to buy more than one of their product. Either way, it's stupid.

GTO47, PLEASE fill us in; do both of your enclosures have the same GUID? This sounds like a job for "Prolific Tech Support" to me! (Seriously, if that's the problem, they should make this right for you.)

gto47 · May 19, 2006, 10:30 PM

Sure enough the GUID is 0x50770E00071002 for both. Guess i'll have to call coolmax and see what they can do for me. I'm not sure if there is anything they can do if all the drives have the same id. Very annoying indeed!