Arm's Cortex A725 Ft. Dell's Pro Max with GB10

Summary

Arm’s 7-series cores started out as the company’s highest performance offerings. After Arm introduced the performance oriented X-series, 7-series cores have increasingly moved into a density focused role. Like Intel’s E-Cores, Arm’s 7-series cores today derive their strength from numbers. A hybrid core setup can ideally use density-optimized cores to achieve high multithreaded performance at lower power and area costs than a uniform big-core design. The Cortex A725 is the latest in Arm’s 7-series, and arrives when Arm definitely wants a strong density optimized core. Arm would like SoC makers to license their cores rather than make their own. Arm probably hopes their big+little combination can compare well with Qualcomm’s custom cores. Beyond that, Arm’s efforts to expand into the x86-64 dominated laptop segment would benefit from a good density optimized core too.Here, I’ll be looking into the Cortex A725 in Nvidia’s GB10. GB10 has ten A725 cores and ten X925 cores split across two clusters, with five of each core type in each. The A725 cores run at 2.8 GHz, while the high performance X925 cores reach 3.9 to 4 GHz. As covered before, one of GB10’s clusters has 8 MB of L3, while the other has 16 MB. GB10 will provide a look at A725’s core architecture, though implementation choices will obviously influence performance. For comparison, I’ll use older cores from Arm’s 7-series line as well as Intel’s recent Skymont E-Core.A massive thanks to Dell for sending over two of their Pro Max with GB10 for testing. In our testing the Dell Pro Maxs were quite quiet even when under a Linpack load which speaks to Dell’s thermal design keeping the GB10 SoC within reasonable levels.Cortex A725 is a 5-wide out-of-order core with reordering capacity roughly on par with Intel’s Skylake or AMD’s Zen 2. Its execution engine is therefore large enough to dip deep into the benefits of out-of-order execution, but stops well short of high performance core territory. The core connects to the ...