If I disable the IOBs in my custom IP, will it still work? What are the IOBs for anyway?

Question

I'm designing an ethernet mac controller which exceeded the number of IOBs in the Spartan 3E starter kit. I'm planning to disable the IOBs.. Will it still work? What are the IOBs for anyway?

Answer 1

It will almost certainly not work if you don't have enough IOBs. IOB = Input/Output Block. It is a block of logic that resides near each pin inside of Xilinx FPGAs. The tools are telling you that you don't have enough pins to accomplish what you need to do. You should create a pinout of your FPGA and map it to the pins on your mac controller. That information is assigned in the UCF (User Constraints File). If you don't have enough pins, you will need to either get a new custom IP that is less resource hungry or get a bigger FPGA.