I've read a few times that a powered USB hub is highly recommended due to the limited power output from the USB ports. I've never had an issue with my USB-CDRW, but then it has a power supply the size of a brick.
Well, it's even worse... I had severe problems with one of my test setups here, which turned out to be a phenomenon of the PSU aging. I had 4.8V on Zorro III, which is already hard on the limit, which went down to 4.3V with a fully loaded Prometheus board. This made the machine going weird.
On USB you have a power budget for distributing "+5V" to connected devices.
This budget assumes that you really have 5V to distribute, not 4.7V. In the end, when a device draws much power (like CDROMs) you may end up in a mess as the voltage goes below the limits.
A powered USB hub is highly recommended in such situations, as well as checking the PSU status with a voltmeter from time to time. An original Commodore PSU (like mine) get to its limits with a PicassoIV, CSPPC, 128MB memory, floppy, one UW SCSI drive, DENEB, Prometheus (including a Voodoo3 and some other cards) :-)
Michael
