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View Full Version : Help! Pathetic USB performance on iMac G5




bigwig
Jan 1, 2010, 10:18 AM
I have an external USB hard drive (WD Elements 1.5TB) and an external DVD drive (LiteOn iHAS422-08 in a Vantec NST-530SU enclosure) hooked up to the USB ports on the back. I can't seem to get more than 5Mb/sec out of them. That's USB 1.1 level performance from these USB 2.0 devices, even though I have no USB 1.1 devices hooked up to the machine (other than the keyboard). Bluetooth is off. I've tried completely powering down but that didn't change anything. What could be the cause of this problem?

iMac G5 Rev B
2GHz PPC
2 GB RAM
OSX 10.5.8



spinnerlys
Jan 1, 2010, 10:29 AM
USB 1.1 had a maximum transfer rate of 12Mbit/s, which would result in 1.5MB/s.

The older PPC Macs don't have very good USB drivers, so the slow speed is expected, but that slow is a bit harsh.

My iBook G4 could give me at least 10MB/s via USB 2.

Have you tried resetting the SMU or another USB port on that iMac?

bigwig
Jan 1, 2010, 10:43 AM
Have you tried resetting the SMCU or another USB port on that iMac?
How does one reset a USB port? I've tried different combinations of USB ports to no avail.

spinnerlys
Jan 1, 2010, 11:02 AM
How does one reset a USB port? I've tried different combinations of USB ports to no avail.

http://support.apple.com/kb/HT1767

But I don't know if that will help, and can also be the external HDD controller that misbehaves.

bigwig
Jan 1, 2010, 12:05 PM
Resetting the SMU made no difference. Argh!