While Intel opted against implementing Hyper Threading for their latest Arrow Lake and Lunar Lake processors, Simultaneous Multi-Threading (SMT) still proves very effective on the AMD side. Even though the top-end AMD Ryzen AI MAX " [1]Strix Halo " SoCs provide 16 Zen 5 cores, the presence of SMT for 32 threads still proves worthwhile from both a performance and power efficiency perspective. Here is an on/off comparison for SMT with the flagship AMD Ryzen AI MAX+ PRO 395 within the HP ZBook Ultra G1a.

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Sixteen physical cores is already double that of Intel's Core Ultra Series-2 "Lunar Lake" processors while with SMT enabled provides for 32 threads. Curious about the performance and power efficiency impact, I ran some benchmarks of SMT enabled/disabled on the HP ZBook Ultra G1a with the AMD Ryzen AI MAX+ PRO 395 under Ubuntu Linux.

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Long story short, SMT remains a very valuable feature for AMD processors. Beyond laptops and mini PCs, even testing on high core count [4]AMD EPYC 9005 CPUs show SMT being a significant win . For HPC users and others preferring against SMT, it can be easily disabled from the BIOS or the "nosmt" Linux kernel boot option.

SMT rounds out the Strix Halo SoC well for 32 threads paired with [5]the very impressive integrated graphics , [6]AVX-512 support , and other design advantages leading to [7]very compelling performance wins .

This SMT on/off comparison testing with the AMD Ryzen AI MAX+ PRO 395 / HP ZBook Ultra G1a was done on Ubuntu 25.04 with the Linux 6.14 kernel. No other changes were made to the hardware/software besides rebooting and toggling SMT support. One item to point out is that when SMT is disabled on Strix Halo, acpi-cpufreq schedutil is used with AMD P-State disabled where as by default amd-pstate-epp powersave is used with how the system firmware is handled. During both rounds of tests the CPU power consumption was monitored using the RAPL sysfs interfaces for measuring the performance-per-Watt impact.



[1] https://www.phoronix.com/search/Strix+Halo

[2] https://www.phoronix.com/image-viewer.php?id=amd-strix-halo-smt&image=ryzen_ai_max_smt_lrg

[3] https://www.phoronix.com/image-viewer.php?id=amd-strix-halo-smt&image=ryzen_ai_max_zbook_lrg

[4] https://www.phoronix.com/review/amd-epyc-zen5-smt

[5] https://www.phoronix.com/review/amd-radeon-8060s-linux

[6] https://www.phoronix.com/review/amd-strix-halo-avx512

[7] https://www.phoronix.com/review/amd-ryzen-ai-max-pro-395