What do the small form-factor, x86 64-bit blade servers reside in Cisco branch-office router?

The Cisco UCS E-Series Servers are purpose-built, small form-factor x86 64-bit blade servers that physically reside inside Cisco Integrated Services Routers (ISR G2 and ISR 4000 series), enabling branch offices to run compute workloads such as virtual machines or applications locally without requiring a separate standalone server.

Cisco UCS S-Series are high-density rack-mount storage servers used in data centers and are not designed to be installed inside a router.

Cisco UCS B-Series Blade Servers require a UCS 5100 Series blade chassis and fabric interconnects and cannot be inserted into a branch-office router.

Cisco UCS C-Series are standalone rack-mount servers deployed in data centers and are not form-factor compatible with installation inside a router chassis.