Necessary to disable "Above 4G Decoding" for View with vGPU?

Hi All,

I am reading through the GRID deployment guide for View 6.2 at the following link:

On page 17, it gives the BIOS recommendations for several server manufacturers. It advises to disable the "Above 4G Decoding" for SuperMicro. This was necessary for XenServer 6.2 where Dom0 was 32bit. In the 64bit Dom0 of XenServer 6.5, it is not necessary to disable this setting. The vmkernel is 64 bit so I want to know if it is really necessary to disable this setting?

On our test SuperMicro, disabling this setting generates an “Insufficient PCI Resources Detected” warning. All the SuperMicro support articles advise to enable “Above 4G Decoding” to resolve this warning message. The BIOS is at the latest version and SuperMicro is straight from the factory and we’ve used this same model for GRID on XenServer 6.2 and 6.5 without issue.

If you have experience with the "Above 4G Decoding" setting for vSphere 6 and View with vGPU, please advise.



Hi Richard,
What happened when you did leave it enabled? Did you discuss with SMicro?

I’m running into exactly the same issue. Did you go back and enable that setting? Do your GRID cards still work fine for vGPU?

Hi All,

I have been pulled onto some other urgent issues but I’ll post my results when I get back to this project.



Any info you could provide would be great. I’m dead in the water at the moment. If this doesn’t work with Supermicro for some reason I need to know so I can move on. Much appreciated.

Found the issue:

MMIO above 4GB not supported. Supermicro has to find a way to allow the server to fully boot if "Above 4G Decoding" is changed to disabled.

here is the answer from supermicro:
vGPU requires above 4g decoding to be ENABLED, while vDGA requires it to be DISABLED