SN770 Vs. SN550: Is Black Better Than Blue?

WD Black SN770 and WD Blue SN550Western Digital’s WD Blue SN550 is an entry-level PCI-Express Gen3/NVMe SSD that was released in late 2019. It has since been revised with lower-end NAND Flash memory and also superseded by both the WD Blue SN570 (2021) and SN580 (2023).

In other words, the WD Black SN770 (launched in 2022) is not a successor to the SN550. It is rather a midrange product that fills a gap between Western Digital’s entry-level WD Blue SSDs and its high-end SN850/850X SSDs. Importantly, the SN770 is also capable of utilizing the newer PCIe Gen4 interface.

What these drives have in common, however, is that they lack onboard DRAM. Instead, they use part of the host system’s RAM as a so-called HMB (Host Memory Buffer) to speed up transfers.

SN770 Vs. SN550: Specifications

This table compares the 2TB capacities of the SN770 and SN550. Full specifications for all available capacities in the respective series can be found at the bottom of this page.

WD_Black 2TB SN770
WD Blue 2TB SN550
Western Digital WD_BLACK 2TB SN770 NVMe Internal Gaming SSD Solid State Drive - Gen4 PCIe, M.2 2280, Up to 5,150 MB/s - WDS200T3X0E
Western Digital 2TB WD Blue SN550 NVMe Internal SSD - Gen3 x4 PCIe 8Gb/s, M.2 2280, 3D NAND, Up to 2,600 MB/s - WDS200T2B0C
Form Factor
M.2 2280
M.2 2280
Interface/Protocol
PCIe 4.0 x4 / NVMe 1.4
PCIe 3.0 x4 / NVMe 1.4
SSD Controller
Proprietary WD/SanDisk
Proprietary WD/SanDisk
DRAM
N/A
N/A
NAND
112L BiCS5 TLC
96L BiCS4 TLC
Sequential Read
5,150 MB/s
2,600 MB/s
Sequential Write
4,850 MB/s
1,800 MB/s
Random Read
650K IOPS
360K IOPS
Random Write
800K IOPS
384K IOPS
Endurance Rating
1,200 TBW
1,200 TBW
Warranty
5 Years
5 Years
WD_Black 2TB SN770
Western Digital WD_BLACK 2TB SN770 NVMe Internal Gaming SSD Solid State Drive - Gen4 PCIe, M.2 2280, Up to 5,150 MB/s - WDS200T3X0E
Form Factor
M.2 2280
Interface/Protocol
PCIe 4.0 x4 / NVMe 1.4
SSD Controller
Proprietary WD/SanDisk
DRAM
N/A
NAND
112L BiCS5 TLC
Sequential Read
5,150 MB/s
Sequential Write
4,850 MB/s
Random Read
650K IOPS
Random Write
800K IOPS
Endurance Rating
1,200 TBW
Warranty
5 Years
Shopping Links
WD Blue 2TB SN550
Western Digital 2TB WD Blue SN550 NVMe Internal SSD - Gen3 x4 PCIe 8Gb/s, M.2 2280, 3D NAND, Up to 2,600 MB/s - WDS200T2B0C
Form Factor
M.2 2280
Interface/Protocol
PCIe 3.0 x4 / NVMe 1.4
SSD Controller
Proprietary WD/SanDisk
DRAM
N/A
NAND
96L BiCS4 TLC
Sequential Read
2,600 MB/s
Sequential Write
1,800 MB/s
Random Read
360K IOPS
Random Write
384K IOPS
Endurance Rating
1,200 TBW
Warranty
5 Years
Shopping Links

Last update on 2024-02-29 / Affiliate links / Images from Amazon Product Advertising API

Since the SN770 and SN550 are from different generations and tiers, it is not surprising that the WD_Black SN770 is ahead of the older Western Digital SSD in every measurable way. It uses newer BiCS5 NAND memory chips compared to the SN550’s 96L BiCS4 – at least according to the original spec sheet. The SN550 NAND was allegedly downgraded to an unspecified lesser variety mid-cycle.

Regardless of the changes to the SN550, it is rated at about half of the maximum sequential read speeds compared to the SN770, and the differences in random IOPS performance are also substantial.

Both models are so-colled DRAM-less SSDs, meaning that there is no physical DRAM memory on the M.2 PCB. The result is typically (but not always) reduced performance compared to SSDs with DRAM. As of 2023, the WD_Black SN770 remains among the fastest affordable Gen4 SSDs in the DRAM-less category. 

SN770 Vs. SN550: Performance

SSD specifications are focused on theoretical maximum performance data, which can and usually do differ from synthetic benchmarks and everyday performance in the real world. Note that our testing was done with a 1TB SN550 dating from before the NAND downgrade, and a 2TB SN770, which is marginally slower than the 1TB capacity.

AS SSD

SN770 Vs SN550 AS SSD chart

AS SSD measures sequential performance using incompressible data, resulting in lower numbers than those found on the spec sheets. The SN770 is nevertheless around twice as fast as the SN550 in these results.

CrystalDiskMark

SN770 Vs SN550 CrystalDiskMark sequential performance chart

In CrystalDiskMark, the SN770’s lead is extended to 120% (read) and 146% (write) performance over the SN550.

SN770 Vs SN550 CrystalDiskMark random performance chart

The large difference in sequential transfer rates is evened out with random data, which is generally better at predicting overall real-world performance. 4K Q1T1 read and write performance is about 50% and 36% higher with the SN770 versus the SN550.

Latency/Response Time

SN770 Vs SN550 latency chart

Differences are also less pronounced in terms of latency (here in microseconds), with the WD Blue SN550 not being as far behind the more modern SSD.

SN770 Vs. SN550: Real-World Performance

SN770 Vs SN550 PCMark 10 app startup chart

PCMark 10’s app start-up times are still an overall win for the WD Black, but the web browser loading time differences are largely insignificant.

SN770 Vs SN550 game loading times chart

In the FF 14 standalone benchmark, the SN770 cuts loading times by 24% over the SN550.

Conclusion

WD Black SN770 2TBAs is often the case, real-world data moderates the differences in theoretical maximum performance a great deal. However, the WD Black SN770 is still much faster than the SN550 in a majority of the tests.

Read more:

SN770 Series: Full Specifications

WD Black SN770250GB500GB1TB2TB
Form FactorM.2 2280M.2 2280M.2 2280M.2 2280
Interface / ProtocolPCIe 4.0 x4 / NVMe 1.4PCIe 4.0 x4 / NVMe 1.4PCIe 4.0 x4 / NVMe 1.4PCIe 4.0 x4 / NVMe 1.4
ControllerProprietaryProprietaryProprietaryProprietary
DRAMNoNoNoNo
Memory112-Layer TLC112-Layer TLC112-Layer TLC112-Layer TLC
Sequential Read4,000 MB/s5,000 MB/s5,150 MB/s5,150 MB/s
Sequential Write2,000 MB/s4,000 MB/s4,900 MB/s4,850 MB/s
Random Read240K IOPS460K IOPS740K IOPS650K IOPS
Random Write470K IOPS800K IOPS800K IOPS800K IOPS
Endurance200 TBW300 TBW600 TBW1,200 TBW
Warranty5-Years5-Years5-Years5-Years
MSRP $59.00 $79.00 $129.00 $269.00

SN550 Series: Full Specifications

WD Blue SN550250GB
(WDS250G2B0C)
500GB
(WDS500G2B0C)
1TB
(WDS100T2B0C)
Form FactorM.2 2280M.2 2280M.2 2280
Interface/
Protocol
PCIe 3.0 x4/
NVMe 1.4
PCIe 3.0 x4/
NVMe 1.4
PCIe 3.0 x4/
NVMe 1.4
ControllerWD ProprietaryWD ProprietaryWD Proprietary
DRAM CacheN/AN/AN/A
MemorySanDisk 96L TLCSanDisk 96L TLCSanDisk 96L TLC
Sequential Read2,400 MB/s2,400 MB/s2,400 MB/s
Sequential Write950 MB/s1,750 MB/s1,750 MB/s
Random Read170,000 IOPS300,000 IOPS410,000 IOPS
Random Write135,000 IOPS240,000 IOPS405,000 IOPS
Endurance150 TBW300 TBW600 TBW
Warranty5 Years5 Years5 Years

 

Jesper Berg
Jesper Berg

I got started with PC building in the 3dfx Voodoo era somewhere back in the 1990s, and have been writing for tech publications for a bit more than a decade. In other words old enough to have lost count of the times PC gaming has been pronounced dead.

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