CPU Tests: Synthetic

Most of the people in our industry have a love/hate relationship when it comes to synthetic tests. On the one hand, they’re often good for quick summaries of performance and are easy to use, but most of the time the tests aren’t related to any real software. Synthetic tests are often very good at burrowing down to a specific set of instructions and maximizing the performance out of those. Due to requests from a number of our readers, we have the following synthetic tests.

Linux OpenSSL Speed: SHA256

One of our readers reached out in early 2020 and stated that he was interested in looking at OpenSSL hashing rates in Linux. Luckily OpenSSL in Linux has a function called ‘speed’ that allows the user to determine how fast the system is for any given hashing algorithm, as well as signing and verifying messages.

OpenSSL offers a lot of algorithms to choose from, and based on a quick Twitter poll, we narrowed it down to the following:

For each of these tests, we run them in single thread and multithreaded mode. All the graphs are in our benchmark database, Bench, and we use the sha256 results in published reviews.

AMD has had a sha256 accelerator in its processors for many years, whereas Intel only enabled SHA acceleration in Rocket Lake. That's why we see RKL matching TR in 1T mode, but when the cores get fired up, TR and TR Pro streak ahead with the available performance and memory bandwidth. This is all about threads here, and 128 threads really matters.

GeekBench 5: Link

As a common tool for cross-platform testing between mobile, PC, and Mac, GeekBench is an ultimate exercise in synthetic testing across a range of algorithms looking for peak throughput. Tests include encryption, compression, fast Fourier transform, memory operations, n-body physics, matrix operations, histogram manipulation, and HTML parsing.

I’m including this test due to popular demand, although the results do come across as overly synthetic.

DRAM Bandwidth

As we're moving from 2 channel memory on Ryzen to 4 channel memory on Threadripper then 8 channel memory on Threadripper Pro, these all have associated theoretical bandwidth maximums but there is a case for testing to see if those maximums can be reached. In this test, we do a simple memory write for peak bandwidth.

For 2-channel DDR4-3200, the theoretical maximum is 51.2 GB/s.
For 4-channel DDR4-3200, the theoretical maximum is 102.4 GB/s.
For 8-channel DDR4-3200, the theoretical maximum is 204.8 GB/s.

Here we see all the 4-channel Threadripper processors getting around 83 GB/s, but the Threadripper Pro can only achieve closer to its maximums when there are more cores present. Along with the memory controller bandwidth, AMD has to manage internal infinity fabric bandwidth and power to get the most out of the system. The fact that the 64C/64T achieves better than the 64C/128T might suggest that in 128T there is some congestion.

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