Two budget drives, one real difference
The Adata SU630 240GB and the Kingston A400 240GB sit in the same price bracket — usually $18 to $25 — and do the same job: replacing a spinning hard drive in an older laptop or desktop. Both are 2.5-inch SATA drives, both are DRAM-less, and both will make an old machine feel new for boot times and app launches. The meaningful difference is what’s inside: the SU630 is built around QLC NAND, while the A400 has historically shipped with TLC, though Kingston has changed components under the same SKU over the years.
That NAND difference matters more than the spec sheets suggest.
| Adata SU630 240GB | Kingston A400 240GB | |
|---|---|---|
| Interface | SATA III 6Gb/s, 2.5″ | SATA III 6Gb/s, 2.5″ |
| NAND type | 3D QLC | TLC (varies by batch) |
| DRAM cache | None | None |
| Seq. read (rated) | 520 MB/s | 500 MB/s |
| Seq. write (rated) | 450 MB/s | 350 MB/s |
| Endurance (TBW) | ~50 TBW | 80 TBW |
| Warranty | 3 years | 3 years |
| Typical street price | $18–23 | $20–25 |
Real-world performance: the SLC cache cliff
For light daily use — booting Windows, opening Chrome, loading a game — these drives are effectively identical. Windows boot on either lands around 10–15 seconds versus 40+ on a mechanical drive. Game load times fall within a second or two of each other. If this is all you do, buy whichever is cheaper and stop reading.
The gap shows up on sustained writes. Both drives fake their rated write speed using an SLC cache: a portion of NAND written in fast single-bit mode. Once that cache fills, you write to raw NAND directly — and that’s where QLC hurts. On the SU630 240GB, large file copies of 15–20GB or more can slump to 50–80 MB/s, which is spinning-hard-drive territory. The 240GB capacity makes it worse, since cache size scales with capacity. Restoring a game library from Steam backups or cloning an old drive onto the SU630 is a “start it and walk away” job.
The A400 handles this better — mostly. TLC-based units sustain writes noticeably higher after cache exhaustion, and its 80 TBW endurance rating gives you more headroom for write-heavy use. The catch is Kingston’s component lottery: the A400 has shipped with different controllers and NAND over its life, and some later batches behave more like QLC drives. You can’t tell from the box. It’s a known quirk of this drive, and reviews of a 2019 unit may not describe the 2024 one on the shelf.
Endurance and failure modes
Neither drive is likely to “wear out” in normal use. The SU630’s ~50 TBW rating sounds small, but writing 20GB a day still takes nearly seven years to hit it. The A400’s 80 TBW is more comfortable, and worth caring about if you’ll do frequent large writes.
The realistic failure modes on both are the same:
Sudden power loss. DRAM-less drives with no power-loss capacitors can corrupt data mid-write if the power cuts. Rare on a laptop with a working battery, more relevant in a desktop on flaky power. Don’t use either in a machine where the drive contents are irreplaceable without backups.
Firmware and controller death. Budget drives occasionally just die — not worn out, just dead. This is why the warranty matters. Three years on both, and both companies honor RMAs reasonably. Keep receipts.
QLC degradation under pressure. The SU630’s QLC NAND also reads slower as the drive fills and the cache shrinks. Keep it under 75% full and it’s a non-issue; fill a 240GB drive to the brim and it gets sluggish in ways the A400 doesn’t.
Which to buy
If prices are within a few dollars of each other, I’d take the Kingston A400 for the higher endurance rating and better sustained-write behavior. It’s the safer pick by a small margin, component lottery notwithstanding.
If the Adata SU630 is meaningfully cheaper — and it often is — it’s completely fine for its actual job: a boot drive and game library in a machine that mostly reads. Don’t let QLC scare you off a $19 drive for a laptop you’re keeping alive for another two years.
When to skip both
240GB is tight in 2024. Windows plus a few modern games eats it fast, and these drives get slower as they fill. Before buying either, check two things:
Does the machine have an M.2 slot? If it takes NVMe, a basic 500GB NVMe drive often costs $30–35 — double the capacity, triple the real speed, for ten more dollars. That’s a better spend if the slot exists.
Is a 480–500GB SATA drive on sale? Prices on 480GB-class SATA SSDs regularly dip to $28–32. At that gap, buying 240GB to save $8 is false economy — you get double the space and better sustained performance, since larger drives have bigger caches and more NAND channels.
Both the SU630 and A400 are honest budget drives that do what they claim. Buy the A400 if it’s within $3, buy the SU630 if it’s not, and buy something bigger if your budget can stretch even slightly.
