Comment by fentonc

The Cray PVP line was also doing double precision floating point, and could overlap vector memory operations with math operations. My guess is that you would need a microcontroller operating at several hundred MHz to beat a Cray-1 in practice. The later Cray-1/S and /M variants also supported a 10gbps link to an SSD of several hundred megabytes, which is hard to beat in a microcontroller.