Hi, my old intel based MacBook with usb interfaces can power and use my portable dvd drive without having any issues. However, my m4 MacBook with usb c interfaces cannot. Despite trying various adapter cables (including Apple’s) the drive flashes its light continuously and the Mac doesn’t see it. It looks like the Mac can’t provide enough power.
My next move would be to buy a powered usb hub and connect via that.
There was an issue with M1 (?) iMacs that they could not export sufficient power for Apple Superdrives. I'm surprised if that persists. You can check the power requested and power available in the USB section under Hardware in System Information (Option-click the Apple menu). Since USB PD, via USB-C, can export crazy amounts of power, that shouldn't be the problem.
My M1 MBP happily powers a R/W BluRay drive so I'm slightly suspicious of your drive/cables. A powered hub should be an answer but it would good to understand why the Mac can't do it before spending more money.
And... how old is your drive? Perhaps it doesn't do PD so needs 2xUSB-A style power export. That was the iMac's problem, some obscure part of the standard that doubles the amount of power-export available wasn't implemented.
Here are some answers for Tony:
The external drive dates from 2014 but has never required a double USB input. I guess it pre-dates any PD standard (I assume PD equals Power delivery)
Plugging into the old Mac shows it requires 500 mA which should be easy Peasy for the new Mac
When I try to do the same measurement on the new Mac, it doesn’t even list the drive!
The cables are a 6” USB mini to USB (works fine on old Mac) in series with an apple USBC to USB adapter
Silly question: Sequoia will probably ask whether to allow the drive to connect. If you haven't seen that dialogue, is it hiding somewhere (I think macOS will remember the permission after you have given it once)?
Otherwise, it still sounds like a hardware (probably cable) issue since it doesn't appear in System Information. When you get to the next stage, as you said, 500mA should be available (that's the USB 2 maximum and very common).
Do you have other devices you can use to test the adaptor?
PD is Power Delivery, part of USB 3. I assume that by "USB" you mean the traditional rectangular USB-A connector.
More answers!
Yes, when I wrote USB, I mean USB – A
No, there are no dialogue boxes hiding anywhere.
I have tried mechanical hard drives , video decoders and thumb drives, and all work fine using the adapters.
When trying the DVD drive again on one occasion only the drive started rattling but failed to reach a stable state—-this says to me that is just not getting enough power to cover its start up power demands.
So it looks like it’s either a powered hub or a new DVD drive!
Insufficient power would explain the early failure to connect and hence not appearing in System Info so your conclusion is probably correct. Still a mystery why it worked on the older MacBook though.
Richard I 