With the new AMD [1]EPYC 9005 processors there are SKUs up to 500 Watt with the likes of the [2]EPYC 9965 flagship at 192 cores for Turin Dense cores or 128 Turin classic cores with the [3]EPYC 9755 . But for those looking at upgrading from an existing EPYC 9004 series server and bound by the motherboard BIOS support and/or cooling/power capacity, 400 Watts is a sweet spot. Many of the existing platforms designed for EPYC 9004 Bergamo/Genoa(X) and now extended for EPYC 9005 Turin are limited to a 400 Watt TDP. With the prior [4]AMD EPYC 9655 testing I have already shown off the great Zen 5 uplift when maintaining the same core counts as Zen 4, but even sticking to 400 Watts at the top-end is room for more. The EPYC 9845 is AMD's top-end SKU for 400 Watts or less that allows for 160 dense cores (320 threads) per socket compared to the 128 core [5]EPYC 9754 Bergamo. Effectively the same power level and 25% more -- and better (Zen 5C) -- cores. Plus with EPYC Turin supporting the new [6]AMD P-State CPU frequency scaling driver there is greater headroom in optimizing for power efficiency if so desired. Here is a look at how the AMD EPYC 9845 delivers a great leap to performance and power efficiency for those looking at a surprisingly robust upgrade from prior generation EPYC 9004.

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For those limited by the server platform's electrical characteristics and/or cooling capacity or even at the limits for your rack's available power, the AMD EPYC 9845 can provide a very compelling option while remaining within the 400 Watt TDP envelope. The AMD EPYC 9845 provides 160 cores / 320 threads of the Turin Dense variety, 2.1GHz base clock, 3.25GHz all-core boost speed, and 3.7GHz maximum boost clock. The EPYC 9845 has a default TDP of 390 Watts and a custom TDP range from 320 to 400 Watts. There is 320MB of L3 cache for this processor, 12 channel DDR5-6000 support, and other features in common with the rest of the AMD EPYC 9005 line-up.

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The EPYC 9845 can provide a very meaningful upgrade compared to the Bergamo top-end at 128 Zen 4C cores / 256 threads. Besides 25% more cores and all the great uplift from the Zen 5 architecture, the EPYC 9845 has a 115MHz higher all-core boost speed and 600MHz higher maximum boost clock while also having the 320MB cache compared to 256MB with the Bergamo processor. The EPYC 9754 has a 360 Watt default TDP but can be increased up to a 400 Watt cTDP.

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The EPYC 9845 can run in a 2P server configuration as well for providing up to 320 cores / 640 threads per server while again striking below the 400 Watt threshold. For the purposes of today's testing I was comparing the EPYC 9754 Bergamo and EPYC 9845 Turin processors in a single socket (1P) configuration. These tests were done on the AMD Titanite reference server platform that AMD used for Genoa/Bergamo. With a simple BIOS upgrade, I was able to switch to using Turin CPUs... With this upgrade story, I stuck to using the DDR5-4800 DIMMs as well for both the Bergamo and Turin Dense benchmarking. If wanting an even greater upgrade path, going from [10]DDR5-4800 to DDR5-6000 yields very nice gains with Turin as shown in other articles.

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The AMD Titanite server was running with air cooling, 12 x 64GB DDR5-4800 Samsung memory, and was running Ubuntu 24.10 for fresh benchmarks of an up-to-date Linux stack. I was also using the Linux 6.13 kernel for the latest AMD P-State driver support. The CPU configurations tested for this article included:

EPYC 9754 - The 128-core Bergamo processor with ACPI CPUFreq and the performance governor. Only AMD EPYC 9005 "Turin" and future server processors are defaulting to using AMD P-State with newer versions of the Linux kernel.

EPYC 9845 - The 160-core Turin Dense processor at its default with the amd-pstate-epp driver on Linux 6.13 and the performance CPU frequency scaling governor.

EPYC 9845 - amd-pstate powersave, EPP power, Balanced Mem - If wanting the 160 core upgrade path but also desiring the best energy efficiency, this run represents that with switching over to the powersave governor on AMD P-State while also switching over to the "power" Energy Performance Preference (EPP) and the Balanced Memory Power Profile. See the prior article [12]AMD EPYC Turin Power Profile Selection Impact On Performance & Efficiency for more information on the tuning options and impact on power/performance.

EPYC 9845 - amd-pstate powersave, EPP performance, Balanced Mem - Similar to the above run but keeping to the "performance" EPP value.

EPYC 9845 - acpi-cpufreq performance - For those on an older version of the Linux kernel without amd_pstate driver support or on a server without ACPI CPPC as needed by AMD P-State or just wanting a 1:1 comparison to Bergamo, this run is using the EPYC 9845 while switching back to the ACPI CPUFreq performance configuration as used by the EPYC 9754.

The CPU power consumption, CPU thermals, and performance-per-Watt were all looked at as well as part of this 128-core EPYC 9754 vs. 160-core EPYC 9845 comparison for the 400 Watt server space.



[1] https://www.phoronix.com/search/EPYC+9005

[2] https://www.phoronix.com/review/amd-epyc-9965-ampereone

[3] https://www.phoronix.com/review/amd-epyc-9965-9755-benchmarks

[4] https://www.phoronix.com/review/amd-epyc-9655

[5] https://www.phoronix.com/search/EPYC+9754

[6] https://www.phoronix.com/search/AMD+P-State

[7] https://www.phoronix.com/image-viewer.php?id=amd-epyc-9845&image=amd_epyc_9845_1_lrg

[8] https://www.phoronix.com/image-viewer.php?id=amd-epyc-9845&image=amd_epyc_9845_2_lrg

[9] https://www.phoronix.com/image-viewer.php?id=amd-epyc-9845&image=amd_epyc_9845_3_lrg

[10] https://www.phoronix.com/review/amd-epyc-9755-ddr5

[11] https://www.phoronix.com/image-viewer.php?id=amd-epyc-9845&image=amd_epyc_9845_4_lrg

[12] https://www.phoronix.com/review/amd-power-profile-linux