it really depends on the workload. as other posters have said, not everything can/should be ported to GPU. some scientific calculations are simply not paralleli

it really depends on the workload. as other posters have said, not everything can/should be ported to GPU. some scientific calculations are simply not parallelizable in that way. typically at least in the US there's a mix of GPU-focused machines as well as traditional CPU-focused machines. the leadership class machines (i.e., the machines funded to push the FLOPS records) tend to be highly focused on GPU. one reason is fixed cooling/power availability. I assume these facilities are looking at ARM as a way to save 10-20% on power and thus cram that much more into the facility.