The X7560 lacks the AES instruction and because of that it is very poor for mining and probably the reason for the aeskeygenassist error.

http://www.cpu-world.com/CPUs/Xeon/Intel-Xeon%20MP%20X7560%20-%20AT80604004869AA%20(BX80604X7560).html

The E7-4870 does have the AES instruction but it is not the optimal processor for mining on the DL580 G7. The best is the E7-8837.

http://www.cpu-world.com/CPUs/Xeon/Intel-Xeon%20E7-8837.html

The 10-core processors are worse hashing even if they have two more cores because the processor clock is much lower. The E7-8837 runs at 2.8 GHz on all 8-cores whereas the E7-4870 only runs at 2.53 GHz. I have verified that the E7-4870 is worse than the E7-8837 for mining.

This article explains why: They say L3 cache is king… Is it? http://www.cointainer.life/2018/03/10/say-l3-cache-king

On eBay I have been picking up sets of four E7-8837's for $40 or less.
https://www.ebay.com/itm/LOT-OF-4-Intel-Xeon-E7-8837-SLC3N-24M-Cache-2-66GHz-6-40GT-s-QPI-H567445/292670668001

Be sure to update the BIOS on the HP DL580 G7 before you put in E7-8837 processors. If you don't it will not even boot to the BIOS screen.
https://support.hpe.com/hpsc/swd/public/detail?sp4ts.oid=4142793&swItemId=MTX_0b8f3842a4cd4835b6dd193ee9&swEnvOid=4184

There are a lot of posts here about mining on a HP DL580 G7.

You may want to start on page 30 of this thread and read forward from there.

Selected posts that might be of interest to you:

https://bitcointalk.org/index.php?topic=1955358.msg33071070#msg33071070
https://bitcointalk.org/index.php?topic=1955358.msg36789923#msg36789923
https://bitcointalk.org/index.php?topic=1955358.msg36161105#msg36161105
https://bitcointalk.org/index.php?topic=1955358.msg33628607#msg33628607