Hello Vincent
According to Cisco documentation:
The move from Cisco Secure ACS to Cisco ISE is easy and costefficient.
Cisco ISE runs on the same Secure Network Server (SNS)
hardware platform as the Cisco Secure ACS. Migrate easily with existing
Cisco SNS 3515 and 3595 hardware. The Cisco ISE software is also
supported on VMware.
This was taken from the following documentation:
https://www.cisco.com/c/dam/en/us/products/collateral/security/identity-services-engine/at-a-glance-c45-733506.pdf
I hope this has been helpful!
Laz