AMD responds to Ryzen launch and performance issues

AMD launched their brand new Ryzen platform earlier this month, opening up sales of motherboards and processors generally on 2 March after pre-orders opened up two weeks earlier on 22 February 2017. The platform has barely aged half a month and it’s been dogged by controversy and some teething issues at launch that affect multiple memory vendors and motherboard manufacturers. After a lot of investigation by the tech press and enthusiasts trying to get to the bottom of the poor gaming performance in a few titles, AMD has published a blog post dealing with these issues, and official comment is now available on the company’s position regarding a few problems affecting the platform.

One of the first theories about Ryzen’s odd performance was that the Windows scheduler was broken, and applying workloads where it shouldn’t and putting workloads on different CCX modules when it shouldn’t due to latency penalties. AMD confirmed that they had been looking into the same reports and the same behaviour, and their conclusion is that the Windows scheduler is working as intended. “We do not presently believe there is an issue with the scheduler adversely utilizing the logical and physical configurations of the architecture,” stated AMD technical marketing lead Robert Hallock in the blog post.

Some other pain points for apparent issues in Windows 10 were also addressed, like the inaccurate L3 cache reporting in Windows 10, which doesn’t actually affect results. The performance delta between Windows 7 and 10 was also noted, but AMD stated that “any differences in performance can be more likely attributed to software architecture differences between these OSes.” What this likely means is that Windows 7 and 10 were just designed to suit different architectures, and the way Windows 7 was designed and how it works just so happens to net you a performance boost on Ryzen, to the tune of 15% in some cases.

“Going forward, our analysis highlights that there are many applications that already make good use of the cores and threads in Ryzen, and there are other applications that can better utilize the topology and capabilities of our new CPU with some targeted optimizations. These opportunities are already being actively worked via the AMD Ryzen™ dev kit program that has sampled 300+ systems worldwide,” added Hallock.

There were also concerns about the high reported temperatures within the motherboard BIOS and from monitoring software in Windows. AMD revealed that when designing the Ryzen family, they wanted a set fan curve that would work for all processors regardless of model or wattage. On the R7 1700X and 1800X, the temperature reported in the BIOS and in Windows programs is an offset value. To find the actual package temperature, enthusiasts overclocking these chips need to subtract 20º Celsius from the reported value, as indicated in the following table. In time, this will be fixed in software and in the BIOS to give you a more realistic value, although internally the offset will remain to keep temperatures in check.

Product Name True temperature Offset for fan policy Reported temperature
AMD Ryzen 7 1800X 38ºC 20ºC 58ºC
AMD Ryzen 7 1700X 38ºC 20ºC 58ºC
AMD Ryzen 7 1700 38ºC 0ºC 38ºC

AMD also addressed power plans in Windows 10 and how they affect Ryzen processors. For the moment, the company recommends enabling the High Performance power plan to allow the SenseMI power and frequency management built into the processor to work properly. AMD says this is necessary for two reasons:

  • Core Parking OFF: Idle CPU cores are instantaneously available for thread scheduling. In contrast, the Balanced plan aggressively places idle CPU cores into low power states. This can cause additional latency when un-parking cores to accommodate varying loads.
  • Fast frequency change: The AMD Ryzen processor can alter its voltage and frequency states in the 1ms intervals natively supported by the “Zen” architecture. In contrast, the Balanced plan may take longer for voltage and frequency (V/f) changes due to software participation in power state changes.

AMD plans to have a software update to fix this in Windows 10 in the first week of April. If you have a Ryzen system already, also consider disabling the high performance event timer (HPET), for another speed boost in applications which make use of HPET for Haswell, Broadwell, Skylake, and Kaby Lake processors, but which run slower on Ryzen processors. You lose the ability to overclock the chip using Ryzen Master in Windows, but this is a small price to pay for more consistent performance while AMD works on fixing some of the latent issues. HPET issues will be fixed through updates to the motherboard BIOS.

Finally, AMD also acknowledged that there were games that showed a performance deficit when using SMT, or simultaneous multi-threading. “Based on our characterisation of game workloads, it is our expectation that gaming applications should generally see a neutral/positive benefit from SMT. We see this neutral/positive behavior in a wide range of titles,” wrote Hallock in the same blog post. It’s notable that when Intel launched the Core i7-900 series with the Nehalem family, it brought along hyper-threading (HT) to the desktop market, and in the beginning it was equally problematic for some games which could not schedule threads on different cores properly without knowing the architecture’s topology. Even today, some modern games just function better when running with SMT or HT disabled.

It looks like AMD had to do some damage control because of the massive hype that came with the Ryzen launch, and this kind of acknowledgement from a company that makes hardware a very rare thing. Here’s hoping that things smooth out from here onwards. Our Ryzen review is still in the works, and we’ll have that ready in the near future.

Source: AMD Community