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USB 2 PCI card needing power from the PSU?

P

PowerMacFan

macrumors member
Original poster
Oct 11, 2012
47
0
i ordered a 6 port PCI USB 2 card for my PowerMac G4 MDD it has the 360w PSU.

This USB card has 5 external and 1 internal port it also has a Floppy Power connector on it little did i know when i bought it is actually coming from China.

So here is the question. Do i need to hook Power to this USB card? I have never seen a USB 2 card with a power connector. What Purpose would a Powered USB 2 card offer over a usual USB Card? I already have a 3 port USB card in this mac which came with it but i need more ports and this USB card does not have a power connector.
 
each usb port draws power...beyond a certain number, the pci interface won't give you enough power so you need to connect to the system PSU. This is the same idea that the powered external USB hubs.
 
old-wiz said:
each usb port draws power...beyond a certain number, the pci interface won't give you enough power so you need to connect to the system PSU. This is the same idea that the powered external USB hubs.
Click to expand...

how much power draw will adding the USB card to the PSU take? i have wired both system fans to the 12v power fan header on the motherboard i will have 4 HDDs installed and i have a SuperDrive

I also plan on replacing the fans and also adding new ones 8 fans in all
 
PowerMacFan said:
how much power draw will adding the USB card to the PSU take? i have wired both system fans to the 12v power fan header on the motherboard i will have 4 HDDs installed and i have a SuperDrive

I also plan on replacing the fans and also adding new ones 8 fans in all
Click to expand...

Sorry, I'm not enough of an EE to have the answer..
 
Most USB-cards only have 5 or less ports, each of them designed for 500mA at 5V. Thats 2.5W per port and 12.5W for all of them leaving only 2.5W for the actual USB-chip to make the card comply with the 15W per card PCI spec.

6 ports would push it over 15W into the 25W spec but useing that may create other problems (like restricting the max power for other PCI-cards or even the AGP-card).
 
Bug-Creator said:
Most USB-cards only have 5 or less ports, each of them designed for 500mA at 5V. Thats 2.5W per port and 12.5W for all of them leaving only 2.5W for the actual USB-chip to make the card comply with the 15W per card PCI spec.

6 ports would push it over 15W into the 25W spec but useing that may create other problems (like restricting the max power for other PCI-cards or even the AGP-card).
Click to expand...

so psu connection is required?
 
I guess it would depend how much power each USB device is drawing. If the device is a 3.5" external hard disk with its' own power point connection, it should need any power from the actual USB bus. Likewise, a bus powered mouse would take up less power from the port than a bus powered 2.5" external hard disk.
 
Jethryn Freyman said:
I guess it would depend how much power each USB device is drawing. If the device is a 3.5" external hard disk with its' own power point connection, it should need any power from the actual USB bus. Likewise, a bus powered mouse would take up less power from the port than a bus powered 2.5" external hard disk.
Click to expand...

i have the meyboard/mouse using one of the integraded usb 1.1 ports and my webcam on the other.

i have a canoscon nu1220 usb bus powered scanner not sure what power that uses.

i have a 250gb hdd inside my old xbox 360 hdd case and use the original transfer cable to power it also have a masscool ide hdd enclosure used on occasions
 
so i have installed my USB card and thanks to my HDD caddy 2 more HDDs also added a TEAC CD-RW drive which is 100% Apple supported after making a power extension and power Y-Splitter i got the card plugged into power. However i had issues the 60mm fan in the back was powered by the 12v header on the motherboard by the AirPort Extreme slot. With the fan connected to this header the USB card refused to work when the Power was connected to it unplugging the fan fixed this issue any idea how a measly fan would cause this?
 
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