I’ve run a GPU enabled XenServer 7.0 with 768GB RAM without any issues (Cisco UCS). Although it does list Dell R720 & R730, unless you are experiencing that issue, I wouldn’t bother with it on any other Hosts.
Just out of interest, what CPU do you have installed? Can you give it’s full name? (EG: E5-2670 v4)
With newer Hypervisors you shouldn’t need to do this, but on one of your Hosts, in the BIOS can you try disabling “Memory Mapped I/O above 4GB” and see what happens? As said, you shouldn’t need to do it with newer Hypervisors. If it won’t boot afterwards or throws any errors, just set it back to how it was.
Power Supplies are fine, that’s what I expected.
Can you just confirm how you have the M60 powered up for me? Are you able to take a clear photo? (Feel free to PM me that if you’d rather not post it on here). It’s fairly strait forward, but mistakes can happen, I’ve been there. (JS if you read this, not a word! ;-) )
As your servers are pretty much unusable at the moment, if the BIOS change mentioned above doesn’t do anything, do you have time to remove 1 from the Resource Pool and start again? Reset R730 BIOS to factory default, clean install of XenServer (don’t add it back into the Resource Pool, keep it stand-alone), license XenServer (Enterprise or above), don’t use the memory workaround you mentioned above, fully update XenServer, install latest GRID drivers, build a clean Windows VM (from an .iso, not a pre-built template) with all Windows updates and install GRID drivers, don’t bother with Apps or running it through MCS, just see if the issue remains.
It’s strange you have this same issue on all of the R730s. It’s possible that 1x R730 or M60 may have had an issue if this were only 1 Host, but with it being on all of them, this is far less likely. There is obviously a common issue between them somewhere, something has been connected, installed or configured incorrectly.
How did you get on with Passthrough?