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


View All Comments

  • Nyceis - Thursday, October 1, 2020 - link

    Wonder when the 2TB will be available.... Reply
  • Oxford Guy - Saturday, October 3, 2020 - link

    We hope you won’t notice it’s an EVO. Reply
  • jtester - Wednesday, October 14, 2020 - link

    I am no expert on comparing SSDs, but why are people saying the testing shows that the 970 pro is better to have than the 980 pro? MOST of the charts show the 980 pro well above the 970 pro and even the 970 evo and 970 evo plus above the 970 pro.

    So what am i missing? And although the 970 pro is MLC, a 2tb evo plus would have the same 1200 for writes/endurance, albeit due to twice the space (but the more space is also a plus).

    I actually have a 970 pro ordered because I got a deal where after discounts, even after tax, I am spending only $240. But I made the purchase just based on what people have said before about MLC and the evos needing an SLC cache, etc... But once I looked closer, I realized all of these specs where the evos (970 and 980) seem to be faster and the caches are big for most people.

    hopefully, someone can explain where I know whether to cancel the order and get another evo plus or 980 pro instead... I have asked all over the place online and nobody gives me straight answers.
  • entrigant - Wednesday, November 11, 2020 - link

    So the new Pro is an EVO. Wonderful. This is most disappointing. :( Guess I should stock up on 970 Pro's while I still can. Reply
  • ph1nn - Friday, November 27, 2020 - link

    So basically the 980 Pro is a complete disaster considering the couple year old SX8200 Pro is beating it almost across the board and is half the price. Anandtech is disappointing here they should have been far more critical about this ssd. Reply
  • Krakadoom - Wednesday, January 27, 2021 - link

    I'm getting terrible IOPS numbers on this drive (980 pro 1 tb). Well not terrible, but noticeably worse than my 970 EVO 1 tb (not even the plus model). On the 980 pro: IOPS read at 374.511 and write at 334.228. On the 970 evo: IOPS read at 422.363 and write at 342.529.

    That's both surprising and disappointing. Would not have bought it had I known this, it's advertised as up to 1.000.000 IOPS both read and write. I'm on PCI-E gen 3, so I might as well have spent less on another 970 evo then and gotten better performance.

    Don't see anything from Samsung or anyone else about this issue, apart from there not being a Samsung driver for the 980 pro yet, so it still runs on the standard Microsoft driver, where all my other drives use the Samsung driver. Maybe that's why, but that should have been ready at launch of a flagship product.
  • chickenballs - Sunday, February 21, 2021 - link

    for most ppl the ADATA 8200pro is more than enough and costs half as much Reply

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