Is a SRAM necessary in a cycloneiii?

But cache can compensate this more or less.

We monitor the SDRam acces to see whether the cache size is big enough or not.

If on chip memory is available then unused blocks will be used for cache if possible (it is paid memory)

If you run from SRAM then your application must fit into this chip and fast sram is expensive compared to sdram.

so it realy depends on the application