Testing PCIe 4.0

It's been over a year since the first consumer CPUs and SSDs supporting PCIe 4.0 hit the market, so we're a bit overdue for a testbed upgrade. Our Skylake system was adequate for even the fastest PCIe gen3 drives, but is finally a serious bottleneck.

We have years of archived results from the old testbed, which are still relevant to the vast majority of SSDs and computers out there that do not yet support PCIe gen4. We're not ready to throw out all that work quite yet; we will still be adding new test results measured on the old system until PCIe gen4 support is more widespread, or my office gets too crowded with computers—whichever happens first. (Side note: some rackmount cases for all these test systems would be greatly appreciated.)

AnandTech 2017-2020 Skylake Consumer SSD Testbed
CPU Intel Xeon E3 1240 v5
Motherboard ASRock Fatal1ty E3V5 Performance Gaming/OC
Chipset Intel C232
Memory 4x 8GB G.SKILL Ripjaws DDR4-2400 CL15
Software Windows 10 x64, version 1709
Linux kernel version 4.14, fio version 3.6
Spectre/Meltdown microcode and OS patches current as of May 2018

Since introducing the Skylake SSD testbed in 2017, we have made few changes to our testing configurations and procedures. In December 2017, we started using a Quarch XLC programmable power module (PPM), providing far more detailed and accurate power measurements than our old multimeter setup. In May 2019, we upgraded to a Quarch HD PPM, which can automatically compensate for voltage drop along the power cable to the drive. This allowed us to more directly measure M.2 PCIe SSD power: these drives can pull well over 2A from the 3.3V supply which can easily lead to more than the 5% supply voltage drop that drives are supposed to tolerate. At the same time, we introduced a new set of idle power measurements conducted on a newer Coffee Lake system. This is our first (and for the moment, only) SSD testbed that is capable of using the full range of PCIe power management features without crashing or other bugs. This allowed us to start reporting idle power levels for typical desktop and best-case laptop configurations.

Coffee Lake SSD Testbed for Idle Power
CPU Intel Core i7-8700K
Motherboard Gigabyte Aorus H370 Gaming 3 WiFi
Memory 2x 8GB Kingston DDR4-2666

On the software side, the disclosure of the Meltdown and Spectre CPU vulnerabilities at the beginning of 2018 led to numerous mitigations that affected overall system performance. The most severe effects were to system call overhead, which has a measurable impact on high-IOPS synthetic benchmarks. In May 2018, after the dust started to settle from the first round of vulnerability disclosures, we updated the firmware, microcode and operating systems on our testbed and took the opportunity to slightly tweak some of our synthetic benchmarks. Our pre-Spectre results are archived in the SSD 2017 section of our Bench database while the current post-Spectre results are in the SSD 2018 section. Of course, since May 2018 there have been many further related CPU security vulnerabilities found, and many changes to the mitigation techniques. Our SSD testing has not been tracking those software and microcode updates to avoid again invalidating previous scores. However, our new gen4-capable Ryzen test system is fully up to date with the latest firmware, microcode and OS versions.

AnandTech Ryzen PCIe 4.0 Consumer SSD Testbed
CPU AMD Ryzen 5 3600X
Motherboard ASRock B550 Pro
Memory 2x 16GB Mushkin DDR4-3600
Software Linux kernel version 5.8, fio version 3.23

Our new PCIe 4 test system uses an AMD Ryzen 5 3600X processor and an ASRock B550 motherboard. This provides PCIe 4 lanes from the CPU but not from the chipset. Whenever possible, we test NVMe SSDs with CPU-provided PCIe lanes rather than going through the chipset, so the lack of PCIe gen4 from the chipset isn't an issue. (We had a similar situation back when we were using a Haswell system that supported gen3 on the CPU lanes but only gen2 on the chipset.) Going with B550 instead of X570 also avoids the potential noise of a chipset fan. The DDR4-3600 is a big jump compared to our previous testbed, but is a fairly typical speed for current desktop builds and is a reasonable overclock. We're using the stock Wraith Spire 2 cooler; our current SSD tests are mostly single-threaded, so there's no need for a bigger heatsink.

For now, we are still using the same test scripts to generate the same workloads as on our older Skylake testbed. We haven't tried to control for all possible factors that could lead to different scores between the two testbeds. For this review, we have re-tested several drives on the new testbed to illustrate the scale of these effects. In future reviews, we will be rolling out new synthetic benchmarks that will not be directly comparable to the tests in this review and past reviews. Several of our older benchmarks do a poor job of capturing the behavior of the increasingly common QLC SSDs, but that's not important for today's review. The performance differences between new and old testbeds should be minor, except where the CPU speed is a bottleneck. This mostly happens when testing random IO at high queue depths.

More important for today is the fact that our old benchmarks only test queue depths up to 32 (the limit for SATA drives), and that's not always enough to use the full theoretical performance of a high-end NVMe drive—especially since our old tests only use one CPU core to stress the SSD. We'll be introducing a few new tests to better show these theoretical limits, but unfortunately the changes required to measure those advertised speeds also make the tests much less realistic for the context of desktop workloads, so we'll continue to emphasize the more relevant low queue depth performance.

Samsung 980 Pro Cache Size Effects
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  • Slash3 - Wednesday, September 23, 2020 - link

    Yeah, we may get a few early test case scenarios through an Nvidia demonstration or partner product, but any major release will probably wait to land concurrently with a full fat Directstorage update from Microsoft. I'm looking forward to it, as I've got a pretty fast storage subsystem and very few games take advantage of it even during asset loading.
  • vanish1 - Tuesday, September 22, 2020 - link

    no headphone jack, no purchase.
  • racerx_is_alive - Tuesday, September 22, 2020 - link

    Do we know enough about the new DirectStorage API to make a prediction about how this will perform against the 4.0 Phison controller next year? Seems like that will be a real world situation that will use lots more queues and shift performance towards the Samsung.
  • KenK74 - Tuesday, September 22, 2020 - link

    This product release is a real yawner. I am keeping my 970 Pro's, and will be searching anywhere but Samsung for decent TLC's with Hardware Encryption capability when I need another. Depending on platform, software Bitlocker may not slow the drive down much, or might do so a lot. For laptops, the real problem is the extra CPU power for software encryption that exceeds differences in SSD power among the SSD drives. Yeah, hardware bitlocker has its issues, but it seems the most power efficient option for laptops that need bitlocker. Meanwhile for non-hardware encrypted drives, the SK Hynix P31 looks very good, runs with the PCI4 drives in many aspects,, and has a great price.
  • PopinFRESH007 - Tuesday, September 22, 2020 - link

    Which Phision controller are you referencing? They have multiple PCIe 4.0 controllers and most of them are already available. The E16T has been available in multiple products since early in the year and the E18 is the controller for the recently announced Sabrent Rocket 4 Plus which (on paper) looks to offer better performance than the 980 Pro. The Rocket 4 Plus looks like it should also be available this year and there are a couple of other drives that are expected to launch in Q4 that will also likely be using the E18
  • dudlej84 - Tuesday, September 22, 2020 - link

    I'm confused by the conclusion claiming it regains the performance crown, but the results seem to show it beaten quite often, even by the 970 pro and 970 evo plus in some cases. What am I missing?
  • XabanakFanatik - Tuesday, September 22, 2020 - link

    You're not missing anything, this is just corporate ass-wiping to reward Samsung for their terrible marketing decision to devalue the Pro brand they've been creating for a decade.
  • StrangerGuy - Friday, September 25, 2020 - link

    Besides their flagship phones, I can't think of any Samsung product that aren't terrible in terms of value for money in recent years.
  • alexdi - Tuesday, September 22, 2020 - link

    This is not a Pro drive. "Pro" means it maintains performance. This is a slightly faster Evo Plus and underwhelming for the price.
  • PeachNCream - Tuesday, September 22, 2020 - link

    That is some trash endurance for the price. The performance numbers are okay, but not the slightest bit earth shattering. I guess in the grand scheme of things, there appears to be no really good reason for this drive to even have gone into production for as little as it brings to the table. At least it isn't QLC, but it's pretty obvious that we have reached the end of NAND and need a more durable and higher density storage medium for the solid state side of the equation.

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