With the SSD WD_Black SN770, Western Digital presents a successor to the popular SN750. WD_Black is the name of the fastest drives from Western Digital, regardless of whether they are hard drives or SSDs. The latter are of course faster, and the current launch puts it a step further in the middle class. The M.2 SSD WD_Black SN770 works with PCI Express 4.0 and thus achieves higher speeds than the predecessor SN750, which was still connected to the system with four PCIe 3.0 lanes.
The version with 1 TB was available to us for the preliminary test. According to the data sheet, this is also the fastest, unlike usual, the 2 TB model built with twice the number of chips is listed there as a bit slower.
There is no information about the controller or the memory used. The SanDisk logo is emblazoned on the controller and the individual 1 TB flash chip, but we couldn’t find any information about the type designations. There is no DRAM chip on the board – so it is a counterpart to Samsung’s SSD 980 (without Pro).
Western Digital specifies a mean time to failure (MTTF) of 1.75 million hours, the write load permitted during the warranty period is 600 TB – both are normal values for a current SSD with TLC memory (triple level cells, three bits per Cell).
speed measurements
In benchmark measurements, the SN770 is not in the top group of PCIe 4.0 SSDs: Almost 5.2 GB/s when reading and almost 5 GB/s when writing large files, plus a maximum of 512,000 or 614,000 IOPS – other SSDs with the same Interfaces sometimes reach more than 7 GB/s for sequential operations, the peak value for access to random addresses is 1.3 million IOPS.
According to our measurements, the size of the SLC cache is around a third of the capacity when the SSD is empty. If this SLC cache is full, the write rate drops sharply.
The quality of the SN770 lies elsewhere: In the application benchmark PCmark 10, the SSD achieved 3345 points in the test of its suitability as a system drive, a few more than the previous Crucial P5 Plus leader; Samsung’s SSD 980 Pro scored 2700 points in this test.
Useless gaming mode
A so-called gaming mode can be switched on via the WD SSD management software, which is supposed to reduce the latency of the SSD by switching off the low power states. The SSD should therefore need a little more energy. As with the predecessor, we were not able to measure any changes in speed due to the mode.
The SN770 should be available immediately with capacities between 250 GB and 2 TB, the recommended prices are between 67 and 403 euros. The real shop prices should be significantly lower, since the faster WD_Black SN850 with 2 TB is already available from just under 310 euros (from 306.41 €).
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