This table shows the Cisco high-scale Controllers comparison at a glance:
coming to the 8510 controller it has 2 Connectivity(2*10g) ports which is equal to 20g so it can support that it can support 6000 APs.
| 8500 | 7500 | 5500 | WiSM2 |
|---|
| Deployment type | Enterprise Large campus + SP Wi-Fi | Central site Controller for large number of distributed, controller-less branches | Enterprise Campus and full service branch | Enterprise Campus |
| Operational Modes | Local mode, FlexConnect, Mesh | FlexConnect only | Local mode, FlexConnect, Mesh | Local mode, FlexConnect, Mesh |
| Maximum Scale | 6000 APs 64,000 clients | 6000 APs 64,000 clients | 500 APs 7000 clients | 1000 APs 15,000 clients |
| AP Count Range | 300–6k APs | 300–6k APs | 12–500 APs | 100–1000 APs |
| Licensing | Right to Use (with EULA) | Right to Use (with EULA) | CISL based (unchanged) | CISL based (unchanged) |
| Connectivity | 2x10G ports | 2x10G ports | 8x1G ports | Internal connections to the Catalyst Backplanes |
| Power | AC/DC dual redundant | AC dual redundant | AC (redundant PSU option) | AC/DC Catalyst chassis redundant PSU option |
| Maximum Number of FlexConnect Groups | 2000 | 2000 | 100 | 100 |
| Maximum Number of APs per FlexConnect Group | 100 | 100 | 25 | 25 |
| Maximum Number of Rogue APs Management | 24,000 | 24,000 | 2000 | 4000 |
| Maximum Number of Rogue Clients Management | 32,000 | 32,000 | 2500 | 5000 |
| Maximum Number of RFID | 50,000 | 50,000 | 5000 | 10,000 |
| Maximum APs per RRM Group | 6000 | 6000 | 1000 | 2000 |
| Maximum AP Groups | 6000 | 6000 | 500 | 500 |
| Maximum Interface Groups | 512 | 512 | 64 | 64 |
| Maximum Interfaces per Interface Group | 64 | 64 | 64 | 64 |
| Maximum VLANs Supported | 4096 | 4096 | 512 | 512 |
| Maximum WLANs Supported | 512 | 512 | 512 | 512 |
| Supported Fast Secure Roaming (FSR) Clients* | 64000 | 64000 | 14000 | 30000 |
for more info you can look into the below deployment guide link
http://www.cisco.com/c/en/us/support/docs/wireless/8500-series-wireless-controllers/113695-8500-dg-00.html
