Summary#
The WD_BLACK SN770M is the drive to buy when you want to upgrade the storage in a handheld — a Steam Deck, ROG Ally, Steam Machine, or a Surface. It is a compact M.2 2230 PCIe Gen4 SSD with reads up to 5,150 MB/s, built on trusted SanDisk TLC NAND, and it is a true like-for-like size swap for the small drive these devices ship with.
At a Glance#
Product : WD_BLACK SN770M NVMe SSD
Brand : Western Digital (WD_BLACK)
Best For : Handheld owners upgrading a Steam Deck, ROG Ally, Steam Machine, or Surface
Interface : PCIe Gen4 x4 NVMe, M.2 2230, single-sided
Capacities : 500GB, 1TB, 2TB
Buy Now : View on Amazon
Key Highlights:
- Compact M.2 2230 form factor — the small size handhelds actually use
- Sequential reads up to 5,150 MB/s on the 1TB and 2TB for fast installs and level loads
- SanDisk TLC 3D NAND from a brand gamers already trust for storage
- nCache 4.0 write caching and PCIe Gen4 speed keep it responsive
- Microsoft DirectStorage support for faster asset streaming in modern games
What the WD_BLACK SN770M Is#
The WD_BLACK SN770M is a high-performance internal SSD in the M.2 2230 form factor. That "2230" is the key detail: it is 22mm wide and just 30mm long, far shorter than the 2280 drives that go in desktops. It is the size that fits inside compact devices — the Steam Deck, the ASUS ROG Ally, the Valve Steam Machine's compact slot, and Microsoft Surface — where a full-length 2280 drive simply will not go. The SN770M is also single-sided, keeping all its chips on one face, which is exactly what tight handheld bays need.
On performance, it runs PCIe Gen4 x4 and reaches up to 5,150 MB/s sequential reads on the 1TB and 2TB models. That is lower than a full-size 2280 flagship, but that is the nature of the compact 2230 class — and it is far more speed than any handheld actually needs. What you feel in practice is quick game installs, fast updates, and snappy level loading.
The drive uses SanDisk TLC 3D NAND — SanDisk and WD are the same company, and it is flash from a name with a long storage track record. WD's nCache 4.0 write-caching layer keeps short bursts fast, and the SN770M supports Microsoft's DirectStorage, which lets modern games stream assets from the SSD with less overhead. It is a DRAM-less design, common in the 2230 class, but tuned to stay responsive for the gaming workloads these handhelds run.
Why the 2230 Size Matters#
This is the single most important thing to get right. Handhelds and compact devices use M.2 2230 drives, not the 2280 drives sold for desktops and the PS5. If you buy a 2280 SSD for a Steam Deck or ROG Ally, it will not fit — full stop. The SN770M exists specifically to be the fast, trusted drive in that compact size.
- Steam Deck (LCD and OLED) — a like-for-like 2230 swap for the stock drive.
- ASUS ROG Ally / ROG Ally X — the SN770M is explicitly marketed for it.
- Steam Machine — the console ships with a 2230 drive and this is a natural upgrade; see our best SSD for the Steam Machine.
- Microsoft Surface — the compact 2230 size fits the Surface's M.2 slot.
If your device instead takes a full-size 2280 drive, this is not the one — look at a 2280 flagship like the WD_BLACK SN850X or the Samsung 990 PRO.
How to Pick a Capacity#
The SN770M comes in 500GB, 1TB, and 2TB:
- 500GB — the minimum. Only worth it on a tight budget; modern games are large and it fills quickly.
- 1TB — the sweet spot. Coming from a small stock drive, 1TB transforms a handheld and hits the full 5,150 MB/s read speed. For most upgraders this is the View on Amazon to buy.
- 2TB — for big libraries. The most room, and it keeps the full read speed. Choose it if you keep a large library installed and hate juggling installs.
Coming from the small drive most handhelds ship with, 1TB or 2TB is a transformative upgrade.
Why the SN770M Earns the Recommendation#
The SN770M matters because it brought a trusted gaming brand into the M.2 2230 space, which had been dominated by lesser-known drives. For handheld owners that is reassuring: storage is the one component where a failure means lost saves and re-downloads, and WD_BLACK carries a long reliability reputation with SanDisk NAND behind it. Reviewers routinely pick it as a top 2230 handheld upgrade for exactly that combination of trusted parts, real Gen4 speed, and the correct compact size.
Be realistic about the class: a 2230 drive like the SN770M is DRAM-less and tops out below a full-size 2280 flagship. But inside a handheld, none of that is a limitation you will feel — the speeds far exceed what the device asks for, and the value is in getting a trusted, correctly sized drive that just works.
Pros & Cons#
Pros:
- Correct M.2 2230 size for the Steam Deck, ROG Ally, Steam Machine, and Surface
- Fast Gen4 reads up to 5,150 MB/s — far more than a handheld needs
- SanDisk TLC 3D NAND from a trusted storage brand
- nCache 4.0 and DirectStorage support tuned for gaming workloads
- Single-sided design fits tight handheld bays cleanly
Cons:
- DRAM-less, so it trails full-size 2280 flagships on paper
- Lower peak speed than a 2280 drive (though irrelevant inside a handheld)
- Only useful for 2230 devices — it will not fit a desktop or PS5 2280 slot
- The 500GB model fills up fast with modern games
Final Verdict#
Buy it. The WD_BLACK SN770M is the smart, trusted way to upgrade the storage in a Steam Deck, ROG Ally, Steam Machine, or Surface. It is the right 2230 size, it is genuinely fast, and it comes from a brand with a real reliability track record. For most upgraders the 1TB is the sweet spot, with the 2TB there if you keep a large library installed.
Upgrading a handheld or console? See our best SSD for the Steam Machine and the best M.2 2230 SSD for the Steam Deck and ROG Ally. For a full-size 2280 upgrade instead, compare the WD_BLACK SN850X and Samsung 990 PRO.
Ready to buy? Grab the WD_BLACK SN770M (View on Amazon).