Great, thank you very much, that works, 8 channels of ADAT I/O!
People use PD with a ARM Cortex M7 (~160 MFLOPS) https://forum.electro-smith.com/t/plugdata-new-pd-environment-that-can-flash... then an SGI Octane should still be good too. The R14000 has two FPUs with 64bit (double-precision) running at clock speed per FLOP, so an Octane with Dual R14000 @ 600MHz has a theoretical 2.4 GFLOPS, not bad for a vintage workstation :)
Thank you, Wolfgang