SPEC2017 Single-Threaded Results - AMD Zen 4 Ryzen 9 7950X and Ryzen 5 7600X Review: Retaking The Hi

SPEC2017 Single-Threaded Results

SPEC2017 is a series of standardized tests used to probe the overall performance between different systems, different architectures, different microarchitectures, and setups. The code has to be compiled, and then the results can be submitted to an online database for comparison. It covers a range of integer and floating point workloads, and can be very optimized for each CPU, so it is important to check how the benchmarks are being compiled and run.

We run the tests in a harness built through Windows Subsystem for Linux, developed by Andrei Frumusanu. WSL has some odd quirks, with one test not running due to a WSL fixed stack size, but for like-for-like testing it is good enough. Because our scores aren’t official submissions, as per SPEC guidelines we have to declare them as internal estimates on our part.

For compilers, we use LLVM both for C/C++ and Fortan tests, and for Fortran we’re using the Flang compiler. The rationale of using LLVM over GCC is better cross-platform comparisons to platforms that have only have LLVM support and future articles where we’ll investigate this aspect more. We’re not considering closed-sourced compilers such as MSVC or ICC.

clang version 10.0.0
clang version 7.0.1 (ssh://git@github.com/flang-compiler/flang-driver.git
 24bd54da5c41af04838bbe7b68f830840d47fc03)

-Ofast -fomit-frame-pointer
-march=x86-64
-mtune=core-avx2
-mfma -mavx -mavx2

Our compiler flags are straightforward, with basic –Ofast and relevant ISA switches to allow for AVX2 instructions.

To note, the requirements for the SPEC licence state that any benchmark results from SPEC have to be labelled ‘estimated’ until they are verified on the SPEC website as a meaningful representation of the expected performance. This is most often done by the big companies and OEMs to showcase performance to customers, however is quite over the top for what we do as reviewers.

Starting off with single-threaded performance in SPECint2017, we can see that AMD's new Zen 4 core performs when compared directly with its previous Zen 3 and even more so, its Zen 2 microarchitecture. In 500.perlbench_r, the Ryzen 9 7950X has a 27% uplift over the previous Zen 3 based Ryzen 9 5950X, with a massive 94% uplift in single-threaded performance over the Zen 2 based Ryzen 9 3950X. This in itself is impressive, with similar levels of performance increase in other SPECint2017 tests such as a 23% increase over the previous generation in 525.x264_r and 30% in the 548.exchange2_r test.

The performance increase can be explained by a number of variables, including the switch from DDR4 to DDR5 memory, as well as a large increase in clock speed.

Moving onto our SPECfp2017 1T results, we see a similar increase in performance as in the previous set of 1T-tests. Focusing on the 503.bwaves_r, we are seeing an uplift of 37% over Zen 3. Interestingly, the performance in 549.fotonik3d, we see an increase of around 27% over the Ryzen 9 3950X, although Intel's Alder Lake architecture which is also on DDR5 is outperforming the Ryzen 9 7950X.

Perhaps the biggest increase in Zen 4's improvement in IPC over Zen 3 is through doubling the L2 cache on the 7950X (16MB) versus the 5950X (8MB). Similarly, both the Ryzen 9 7950X and 5950X have a large pool of L3 cache (64MB), but the 7950X boosts up to 5.7 GHz on a single core providing the core temperature is below 50°C, or 5.6 GHz if above 50°C. 

As it stands at the time of writing, AMD's Ryzen 9 7950X is the clear leader in single-core IPC performance, with a pretty comprehensive increase in IPC performance over Zen 3. Although Intel's Alder Lake (12th Gen) provided gains over AMD's Ryzen 5000 series in a multitude of ways including frequency, optimizations, and its complex hybrid architecture. There is no doubt that the latest Zen 4 microarchitecture using TSMC's 5 nm node gives AMD the single-thread performance crown, and in terms of single-threaded applications, it's the most powerful x86 desktop processor right now.

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