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Debut of EPYC as a Compucon Server Series Print
October 2018
2018-1020 First posted

A new server processor, the EPYC series from AMD, has been available in the supply chain for more than a year now and this processor has not been picked up on this forum previously until now. Should we know about this processor series? Why did this forum not discuss it till now?

Intel Xeon processors have dominated the market for over a decade and so the emergence of a new server processor from AMD might be considered an event but not an advent. AMD recently published a theoretical study indicating that EYPC would achieve the same or higher level of performance and productivity than Xeon for the same or less price in terms of Total Cost of Ownership (TCO). Though it was a marketing piece, it did contain enough arguments to support its claims. Perhaps it is a wake-up call to the market and so this forum wakes up. Ref:

EPYC is a multi-chip module processor meaning that the processor is not made of one die but is a package of multiple dies. This approach allows more processor cores to be packaged without incurring the high cost of fabricating high core density dies. The concept may be simple, but can it be implemented well in practice?

This is what the Compucon team has done recently by hands-on benchmark testing (in September and October 2018) to find out the productivity of the implementation. The test sample is the EYPC 7351P- single socket, 16 cores, 32 threads, 64MB L3, and 2.4GHz base frequency supporting 8 channels of DDR4 memory transfer and 128 PCIe links with a TDP of 155W. It is made from a 14nm manufacturing process. This specification is very impressive.

Compucon tested the EPYC with a popular open source scientific and mathematical application called Cholesky Factorization. The runtime using 16 cores achieved a speed up of 15.8 times over 1 core. This is a very high score; though not a perfect score, perfection is not achievable in real life. In fact, this application requires data to be transferred between cores before computing can proceed during the entire computing process, and data transfer took up some clock time. If the application does not need inter-core data transfers, the speed up may reach 15.99 or something along those. The test result confirms that the multi-chip packaging arrangement has not introduced extra latency to computation and this is good.

EPYC has 2 other merits over Xeon. One is the higher memory bandwidth from 8 channels. Xeon has 6 channels only. The other one is the support of 128 PCIe links by a single socket processor. This quantity is higher than that supplied by 2 Xeon sockets. A GPU card needs 16 of them, so a single socket motherboard has more than enough bandwidth to support 4 GPU cards and more, subject to the real estate of the motherboard form factor and the intended design criteria decided by the motherboard maker.

All in all, EPYC is impressive.