Pegasus R4 can not be mounted/not displayed

  • Last Post 26 February 2018
Cornelius Fischer posted this 22 February 2018

Hi all

since upgrading from OSX 10.12.6 to OSX 10.13.3, the kernel extension PromiseSTEX.kext does not load on booting my MacPro. When using the trick below (from another thread), I can manually load the extension and bring my Pegasus R4 back online.

Unfortunaly, when my MacPro goes to sleep, the kernel extension again gets lost, and therefore also my Pegasus R4 gets lost.


I'm running my Pegasus R4 with the latest firmware 5.04.0000.61 and the Promise Util with 4.02.0000.10

My subsystem details can be found here (can not attach the file..)


I'm desperately looking for help to solve this issue, as I can't work like that.


Thanks for any adivse in permanently solving my issue.



Hi Philippe,

Have you tried loading the kernel extension?

sudo kextload /Library/Extensions/PromiseSTEX.kext

Then you can verify in the Terminal by querying the bundle ID:

kextstat | grep com.promise.driver.stex

The output should be:

47 0 0xffffff7f80f73000 0xb000 0xb000 com.promise.driver.stex (5.2.10) D5918F4B-6516-32DF-855F-E4CBE26067CD <46 12 5 4 3>

If you get the above, that means you loaded it successfully. You should also refresh System Information after you've done the above. You should see that the PromiseSTEX is loaded.

kextload man page
kextstat man page





Venkatachalam Settu posted this 26 February 2018

Hi Cornelius,

You can call technical support at 408-228-1500 or reach out through support case at

Thank you.