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We are using Cables Unlimited USB-2925 USB-to-Dual-DB9 serial cables, which use the Moschip MCS7720 controller. We have downloaded the newest driver from, but that driver was last updated in 2005. It does not seem to be working with Macs running OS X 10.6 Snow Leopard.

Does anyone know of any updates for this driver, or are there any ways to get the driver to work with Snow Leopard?

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up vote 2 down vote accepted

There is a solution to force this exact cable to work with Snow Leopard while waiting for Moschip to update their drivers.

Be very careful while you are making this change. You will need to execute these commands as the root user.

  1. Install the latest driver from Moschip and reboot.

  2. Locate the file /System/Library/Extensions/MCS7720Driver.kext/Contents/Info.plist

  3. Open the file and locate the line that reads <integer>30496</integer>

  4. Change the number from 30496 to 30485. Save the file.

  5. Execute the command "touch /System/Library/Extensions".

  6. Wait a few minutes and plug in your USB cable. You should see a screen pop up that alerts you that two new network interfaces have become available. You'll note that they're named /dev/tty.USB-Serial0.0 and /dev/tty.USB-Serial1.1.

  7. You're good to go. If the software is ever updated by Moschip, it will likely overwrite this change.

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