Re:HPC Systems Special Offer: Two A64FX Nodes in a 2U for $40k
by brandmeyer on Wednesday August 26, 2020 @11:11AM
(#24283149)
SVE is considerably richer than AVX-512, IMO. Its got better unaligned load/store support (especially on A64FX) and richer instructions for generating and manipulating masks.
For example, SVE has mask partitioning and speculative vector load instructions to accelerate data-dependent loop termination. You can do a vector-length-agnostic strncpy on SVE without too much effort.
Re:HPC Systems Special Offer: Two A64FX Nodes in a 2U for $40k
by sonium on Wednesday August 26, 2020 @11:25AM
(#24283286)
Quantum chemistry software benefits from 'stupid-high bandwith RAM'. It says Gaussian supports this hardware. I remember when running VASP (another popular quantum chemistry software) we were not even using all the cores on a node, because the limited performance of the RAM interface.
The basic operation they perform is fast fourier transform on large (number of electrons of the system ^ 2) matrices.
Re:HPC Systems Special Offer: Two A64FX Nodes in a 2U for $40k
by formerly_proven on Thursday August 27, 2020 @06:12AM
(#24292013)
HBM2 is totally tame in terms of signalling rate. I think it's like 2 GT/s, while GDDR6X is at 20 GT/s (both per pin). PCBs aren't too slow for HBM2, a silicon interposer is just the only practical way to route a memory interface using something like 7000 pins directly between wafers. If HBM2 chips were using regular packaging and pitches suitable for PCB use, each stack would have to be a huge package with thousands of balls.
Re:HPC Systems Special Offer: Two A64FX Nodes in a 2U for $40k
by beached_whale on Wednesday August 26, 2020 @12:19PM
(#24283931)
In concurrent/parallel scenarios the memory bandwidth is often the bottleneck. So 1TB/s of memory bandwidth over 96 threads is about 10.5GB/s each. Not great, but the 3990x has what, 100GB/s over 64 threads for about 1.5GB/s each?
Your implication is correct however. x86 is more in line with "typical" consumers, and even businesses, who need this kind of compute.
Dell's C6525 quad-node dual-socket EPYC is a good example of what a typical compute-oriented build: https://www.servethehome.com/dell-emc-poweredge-c6525-review...
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A64FX is an HBM2 box. Its a normal CPU (not a GPU), with access to that stupid-high bandwidth RAM. There's probably a few use cases where the high-bandwidth becomes a major advantage.
A64FX compares against the NVidia V100 on a memory-bandwidth and memory-capacity basis (and is approaching GPU-level FLOPs thanks to SVE 512-bit SIMD units). Except its running the ARM instruction set. As others have pointed out, this thing is like Xeon Phi 2.0, except with the notable niche that its the #1 supercomptuer in the world right now.