That doesn't sound that super to me! "100 times faster than a phone" just doesn't have an impressive ring to it.
https://arstechnica.com/science/2017/08/spacex-is-launching-...
It's sort of funny how many of the flaws of old computing hardware turned out to be hugely beneficial for use in space. Bulky transistors that are relatively safe from bit flipping, high power draw that means small fluctuations don't cause outages, limited processing and storage that forced efficiency and lowered the amount of stuff exposed to radiation.
I'm not sure where the tipping points would be, but it wouldn't surprise me if getting a 386 working in space is easier than getting a Pentium 4 to achieve the same things.
The Spaceborne Computer includes the HPE Apollo 40 class systems with a high speed HPC interconnect running an open-source Linux operating system. Though there are no hardware modifications to these components, we created a unique water-cooled enclosure for the hardware and developed purpose-built system software to address the environmental constraints and reliability requirements of supercomputing in space. Generally, in order for NASA to approve computers for space, the equipment needs to be “ruggedized” – or hardened to withstand the conditions in space.
https://news.hpe.com/hewlett-packard-enterprise-sends-superc...
For that matter, it doesn't look like stage one of putting a supercomputer into space. (And really, why would you want that?) From that last paragraph, its tasks from now on will be running sample takeoff and landing calculations, which implies this is about testing whether modern tech can replace existing flight computers.