I have run Blackmagic on USB 2, thumb drives, USB 3, and USB C devices to see if I’m getting my money’s worth. On an older MacBook Pro the rates I see are 500 MB/S both read and write, as you would expect. I have tried this on my older mackbooks with SSD and they do scale down as the device is older. On my 2016 MacBook Pro, I am seeing speeds like 1,000+ MB/s write, and 1100+ MB/S read. Since the “volume” is on your Startup Disk, you will see how fast it drive is. In Blackmagic select the disk image mounted.

Mount the volume (if it is not already mounted). Make it big enough for Blackmagic to work with (7+ GB) and name it what you will. Create a disk image (.dmg) using the disk utility specifying file->new image->blank image.

I found a workaround that will report the rates of the Startup Disk. When Blackmagic tries to read the Startup Disk, you get the message that the device is not writeable, hence you cannot rate the the transfer rates of the drive. Blackmagic is now faster enough to rate internal SSD speeds, even the Startup Diskīlackmagic has been updated to adequately report the speed of SSD devices.

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