I think I get it. I've tried microblaze-v for a while now. And just look at their interrupt handler. https://github.com/Xilinx/embeddedsw/blob/master/lib/bsp/sta... . With the FPU enabled at compile time, that's > 128 memory ops per interrupt. That's insane, especially without an NVIC and chaining and all that. My latency was astronomical, and my maximum interrupt frequency was pitiful. Ended up doing the work (sw and hardware options) to get it to operate more like arm-m, but arm-m doesn't need that work to be done. NVIC is always NVIC, and NVIC is good