Under Linux, I have 6 Nvidia cards working. Not sure what is up with the Proliant G7 series. I have tried a DL360, DL380 and the DL580 and none of these will boot with more than 4 GPUs installed. Windows will lock up at loading screen.
Slap a USB stick with HiveOS on it and 6 get recognized easily.
I have a ML350P G8 that has taken 6 GPUs in windows easily.
Edit* Make that 9 1060s in one 580 in HiveOS.
I hit a wall at 9 cards on the 580 also, using SMOS. Spent countless hours getting 9 cards to work. In one way i love the HP servers, H/s on cryptonight is a bonus but as a gpu-mining platform they look good on paper but is in my experience not fun maintaining. Did anyone try to run Windows 10 on the 580 with success?
That is a problem with the HP server series like the G7 which are a bit old so HiveOS maybe does not have the best support for them. I will also blame HP or any other old server like Dell as I have tested HiveOS with 12 RX 580 cards in ASUS B250 Pro Mining and they worked out of the box perfectly without problems with a great hashrate of 360 Mhs.
The strong Xeon processors are good to mine Bytecoin or Monero.