Price When Reviewed

250GB/$59, 500GB/$79, 1TB/$129, 2TB/$269

WD's new Black SN770 is a PCIe 4.0 NVMe SSD that competes nicely with similar mid-tier products in both price and performance. It's also further proof that DRAM-less SSD design can be very effective in systems that support it. It won't win any races against some of the luxuriously priced hot rod-type SSDs out there, but the WD Black SN770 is fast and affordable. You'll have no complaints if you slap one into your PC.

This review is part of our ongoing roundup of the best SSDs. Go there for information on competing products and how we tested them.

Design and features

DRAM-less design means that the SN770 uses host buffer memory (HBM), i.e. your computer's memory as primary cache. The controller is a proprietary WD/Sandisk design and the NAND is 112-layer TLC according to the company. Note that the image below pictures the included heat spreader; our test unit arrived with chips exposed.

While host bus memory, which was added to NVMe as of version 1.2, didn't perform very well on the first such drives we tested, it seems to have come of age with the WD Black SN770 and the recently tested Adata Atom 50. Seemingly, it took the controller folks a while to come to grips with practical implementation.

Note that the Sony Playstation 5 does not support HBM. If you're thinking of the SN770 (or Atom 50) for use in that console, expect lesser performance, though the secondary caching (TLC used as SLC for faster writes) should allow it to perform adequately.

The SN770 is available in 250GB/$59, 500GB/$79, 1TB/$129 (tested), and 2TB/$269 flavors. The drives are warrantied for 5-years or 200TBW, 300TBW, 600TBW, and 1200TBW (TeraBytes Written over the life of the drive) respectively–about average given the price. Yes, you get a bit more TBW per GB with the 250GB version.

According to WD's reviewer's guide specs, the 500GB version will be slightly slower, and the 250GB version will offer about half the write speed and 75% of the read speed. That's still very fast, though if you can afford the 1TB or 2TB models, we recommend those for the best overall experience.

Performance

WD talks up the SN770 being “faster” in its advertising literature, but that's largely in comparison to older SSDs using the slower PCIe 3.0 bus. Over PCIe 4, while it's an all-around good performer (especially in real world transfers), it's hardly the fastest drive to enter our test facility.

CrystalDiskMark 6, shown below, rated the WD Black SN770 as faster than the similar Adata Atom 50 in sustained throughput, though not by much.

As you can see below, the SN770 was a bit slower in our 48GB transfer tests than the Atom 50, but it still racked up a fifth place finish among the thirty some odd drives we've tested. As both the Atom 50 and the SN770 are HBM drives, it's fair to assume that using system memory is having a net positive effect on small file performance—at least over the faster PCIe 4 bus.

The WD Black SN770 really fell off the pace in our single large 450GB file write–a sure sign that it ran out of secondary TLC-as-SLC cache.

Below is the screen capture of the 1TB SN770 running out of secondary cache at around the 375GB mark. This is hardly unus ual, and few users will ever write that large a file, though top-tier drives will handle it better.

The 2TB SN770 wouldn't suffer a slowdown in this test, while the 250GB and 500GB models will run out of secondary cache far sooner. And yes, the 250GB drive is too small for this test.

The SN770 ran relatively cool in our tests and is a good everyday performer, if not quite as good as the competing Adata Atom 50. Subjectively, you will never notice the difference.

PCIe 4 testing is done on an MSI MEG X570 motherboard socketing an AMD Ryzen 7 3700X 8-core CPU, using 64GB of Kingston 2666MHz DDR4 memory, and an AMD Radeon RX 480 graphics card. ImDisk facilitates the 58GB RAM disk used for the 48GB transfer tests. All testing is performed on an empty, or nearly empty drive that's TRIM'd after every set of tests. Performance of any SSD will decrease as you fill it up.

Write performance will decrease as the drive fills up. Also, in rare cases, components may change for the worse. WD would not promise that the SN770's components would not change over time, however, our experience with the company would indicate that performance will remain equal even if they do. Our standard warning with all drives is that, if, given similar hardware, they do not perform as well as our test unit, let us know.

A solid bargain

Though WD has sexy-ed it up in its advertising, the Black SN770 is merely an average PCIe 4 NVMe SSD in terms of performance. However, “merely average” among PCIe 4 NVMe SSDs is very, very fast in practical terms, and WD priced this drive to move–you'll have no complaints if you buy one for your PC. That said, consider an SSD with a traditional DRAM design if you're looking to upgrade a PlayStation 5's storage.

At a glance

Expert's Rating

Pros

• Excellent real world performance
• PS5 compatible
• Affordable

Cons

• A couple of GBps slower on PCIe 4 synthetic benchmarks
• Uses host memory bus (HMB) rather that onboard DRAM, though seemingly without the usual performance penalty.
• PS5 doesn't support HMB

Our Verdict

The Atom 50 was second-tier on synthetic benchmarks, but tied for number one in our real life transfer tests over PCIe 4. Nice. It's affordable and PS5 compatible, but uses HMB (your PC's DRAM) for primary cache, which the PS5 does not support. Hence, there might be a small drop in performance inside Sony's console.

Price When Reviewed

$120 for 1TB, $250 for 2TB

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The Adata Atom 50 is one of the more affordable PCIe 4 SSDs on the market, which would seemingly make it a nice option for the PlayStation 5. It's second-tier over PCIe 4, according to synthetic benchmarks, but it tied for 1st place in our real world 48GB transfers–a eye-opening performance considering the price.

Even more impressive, the Atom 50 managed that feat without a DRAM cache. It instead utilizes HMB (Host Memory Bus, aka your computer's RAM) primary caching, a technology we've seen less than stellar results from previously. Alas, Sony's FAQ says thePS5 doesn't support HMB, which means the Atom 50 may not be quite as fast inside that console.

Design and specs

Adata's Atom 50 bucks the trend of bargain SSDs based on Phison-based designs by employing a RealTek RTS5766DL to shuttle data to and from the SSD's 176-layer TLC (Triple-Level Cell, 3-bit/state) NAND. As you'll see below in the performance section, it proved very proficient.

As noted, there's no DRAM cache, Adata instead opting for HMB. Also as mentioned, this is the first time we seen HMB perform up to snuff.

The Atom 50 is currently available in 1TB/$120 (tested) and 2TB/$250 flavors. That's a hair pricy for a bargain PCIe 4 SSD, but it's still in that ballpark and doesn't consider any discounts you might see. The drives are warrantied for five years or 650TBW (TeraBytes Written over the life of the drive) per 1TB of capacity. That latter is about average for the price point.

Performance

The Atom 50 turned in good PCIe 3 numbers and decent second-tier numbers over PCIe 4 in CrystalDiskMark 6, CrystalDiskMark 7, and AS SSD 2. Those benchmarks rate the fastest PCIe 4 NVMe SSDs during sustained transfers at around 7GBps while the Atom 50 was just below 5GBps.

I should mention that second-tier NVMe is still quite good in the grand scheme of things and the norm at the Atom 50's price point. It was easily the match of the equally bargain Sabrent Rocket 4 as shown in the CrystalDiskMark 6 numbers below.

Where things got interesting were during our 48GB real world transfers shown below. The Atom 50 over PCIe 4 actually tied the Corsair MP600 Pro XT for the fastest aggregate time (1 minute, 39 seconds) we've seen.

Looking at the Atom 50's PCIe 3 48GB numbers, which aren't bad but hardly record-setting, I'm thinking that HMB might be a lot more effective over the faster PCIe 4 bus than it was over PCIe 3.

The Atom 50 turned in an average time writing our single large 450GB file over PCIe 4, though it never slowed down handily outpaced the Crucial P5 Plus. The 450GB write tests secondary caching algorithms and the speed of the NAND. Keep in mind that the Atom 50 we tested was only a 1TB drive while the Sabrent Rocket 4 it nearly matched was a 2TB unit.

I found little to complain about with the Atom 50's performance, even if it couldn't match the 7GBps that top-tier SSDs deliver on synthetic benchmarks or their super-fast sustained 450GB writes (191 to 215 seconds). How often do you write 450GB? That said, consider the FireCuda 530 or MP600 XTs if every second counts, otherwise save money with the Atom 50.

The PCIe 3 tests utilize Windows 10 64-bit running on a Core i7-5820K/Asus X99 Deluxe system with four 16GB Kingston 2666MHz DDR4 modules, a Zotac (Nvidia) GT 710 1GB x2 PCIe graphics card, and an Asmedia ASM3242 USB 3.2×2 card. It also contains a Gigabyte GC-Alpine Thunderbolt 3 card, and Softperfect Ramdisk 3.4.6 for the 48GB read and write tests.

The PCIe 4 testing was done on an MSI MEG X570 motherboard socketing an AMD Ryzen 7 3700X 8-core CPU, using the same Kingston DRAM, cards, and benchmark software. ImDisk replaces Softperfect as the RAM disk. All testing is performed on an empty, or nearly empty drive that's TRIM'd after every set of tests. Performance of any SSD will decrease as you fill it up.

Write performance will decrease as the drive fills up. In some rare cases, components may change for the worse. Adata promises that the components in the Atom 50 will not change over time. However, our standard warning with all drives is if , given similar hardware, does not perform as well as our test unit, let us know.

Excellent for the money

The Atom 50 is an excellent bargain and a good fit for your PC. It will work in your PS5, however, you might not see exactly the same performance. Still, this is a nice effort from Adata and the best HMB NVMe drive we've tested to date.