Avantek's Arm Workstation: Ampere eMAG 8180 32-core Arm64 Review
by Andrei Frumusanu on May 22, 2020 8:00 AM ESTSPEC2017: Weak ST Performance
Single-threaded performance of the system is going to be interesting, but given the age of the CPUs we shouldn’t be expecting any miracles.
As comparison points, I’m adding the new Neoverse-N1 based Graviton2 results, which should server as an indicator what a contemporary Arm core should be able to achieve, as well as Intel’s i7-10700K (Equivalent to an 9900K) – a common mainstream consumer-grade CPU that should represent your higher-end x86 desktop machine.
Things aren’t looking too well for the Skylark cores, as performance isn’t really up to par with more recent generation hardware. There’s no specific workload in which the eMAG does badly in, but we do see that small memory footprint workloads such as 548.exchange2 aren’t faring all that badly – pointing out that for the other workloads the system must be cache and memory bottlenecked.
In the floating point suite, things are again not too great and performance further craters in some tests.
Overall, the eMAG 8180 is extremely disappointing in its single-threaded performance. It’s actually quite intriguing to see the results. Even though the Skylark cores are operating at 3.3GHz, the end performance isn’t any better than a 2.1GHz Cortex-A72 core such as found in the first-generation Graviton chip. That’s quite the massive IPC disadvantage even between those two older CPU microarchitectures, and reminds us of the reason AppliedMicro hadn’t really seen much success with its design.
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SarahKerrigan - Friday, May 22, 2020 - link
The X-Gene microarchitecture was never particularly stellar and by the time eMag rolled around it was woefully obsolete. I did some testing on eMag a few months back and it was pretty dire. When I spent some time on Graviton2 last week, it was like night and day compared to eMag (frequently 2+ times the single-thread perf despite a much lower clock), so I have high hopes for Altra.SarahKerrigan - Friday, May 22, 2020 - link
By the way, Andrei, you may want to correct the ST SPECFP subtest result graph - it looks like you used Graviton as a template and forgot to change the labels to eMag, because right now it only mentions Graviton1, and Graviton2, and Intel, not eMag.Andrei Frumusanu - Friday, May 22, 2020 - link
Thanks, good catch.Flunk - Friday, May 22, 2020 - link
Interesting to see even if this hardware only makes sense for very specialized purposes. ARM processors have gone from only applicable to mobile devices to something that would have made sense in a server a few years ago.SarahKerrigan - Friday, May 22, 2020 - link
This isn't exactly a good representative of ARM processors; chips like Graviton2 are competitive for server workloads today, and make eMag look like a toy by comparison.eastcoast_pete - Friday, May 22, 2020 - link
Thanks Andrei, good and in-depth review! You and others here have already commented on the great difference of this legacy CPU to Ampere's Altra or Amazon's Graviton 2. What I am also very curious about is Fujitsu's ARM-based multicore CPU (A64FX). Amongst other features, it supports 512-bit scalable vector extensions (SVEs), so same width as Intel's AVX512. I wonder if someone at Fujitsu reads Anandtech, and maybe send you a setup for review, although a PRIMEHPC might be out of the scope here. Still, that's an ARM v8 design that should beat the Graviton 2 and the Altra, especially if applications can make use of the wide SVEs.anonomouse - Friday, May 22, 2020 - link
Based on what we know of the A64FX, it’ll almost certainly *only* beat Graviton 2/Altra in cases where it can heavily utilize wide vectors. In all other scenarios it really doesn’t have a lot of execution width, and only runs at 2.2Ghz. The disclosures in their Microarchitecture guide also don’t showcase anything impressive looking on the branch predictor, which is fine for the typical HPC workloads it will run. That thing is very heavily purpose designed for HPC, and it’s clear they focused on that and not general performance.SarahKerrigan - Friday, May 22, 2020 - link
Indeed. It's a specialized chip. I would expect no miracles from it on general-purpose loads.eastcoast_pete - Friday, May 22, 2020 - link
Agree with you and anonomouse on general purpose loads; my interest in wide vectors is mainly due to their utility for video processing and encoding, if (!) the software supports it. For those applications, AVX512 is what keeps Intel competitive with EPYCs in the x64 space. As a question, is anything like an AV1 encoder even available for ARM v8, and specifically to use wide SVEs?Wilco1 - Saturday, May 23, 2020 - link
There are many AV1 codecs which have AArch64 optimizations, but most focus on older mobile phone cores (eg. http://www.jbkempf.com/blog/post/2019/dav1d-0.5.0-... ), so likely need further work on latest microarchitectures with up to 4 128-bit Neon pipes.It's early days for SVE, the first version (as in A64FX) is aimed at HPC. Video codecs will be optimized for SVE2 when hardware becomes available.