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Adata's Ultimate SU900 256GB SSD reviewed

Two bits per cell in three dimensions

When we visited Adata at Computex just a few weeks ago, it was clear that the company's focus was on M.2 and PCIe storage. A representative even went as far as to say that Adata may phase out SATA drives entirely, replacing them with PCIe x2 drives to sate the budget market.

But there's no telling when that day may come. For the time being, Adata is still hard at work designing and releasing upgrades to its existing SATA offerings. We have one such upgrade on hand today: the Ultimate SU900. As outlined in the table below, the lineup includes 256GB, 512GB, 1TB, and 2TB versions.

Adata Ultimate SU900
Capacity Max sequential (MB/s) Max random (IOps)
Read Write Read Write
256GB 560 520 80K 90K
512GB 560 525 85K 90K
1TB 560 525 90K 85K
2TB 560 520 85K 80K

Like the SU800 before it, the SU900 stores your bits in IMFT's 3D NAND. This time around, though, Adata ponied up for MLC chips instead of TLC. This is the opposite of what we've seen most brands do of late—Samsung and Micron both used their respective non-planar technologies as an excuse to move product lines from MLC to TLC. Adata's reversal is a welcome change of pace. The SU900's MLC NAND should yield appreciable speed and endurance increases over the SU800.

Adata could only send us a 256GB sample of the SU900, so we won't have an apples-to-apples comparison against the SU800 512GB we tested some months ago. We'll forge ahead regardless. First, we'll void the warranty and sneak a peek under the hood.

Aside from the upgrade to MLC, little distinguishes the SU900 from the SU800. Silicon Motion's SM2258 is running the show again, and it still offers pseudo-SLC caching for burst performance when the DRAM cache is overwhelmed. The NAND dies are distributed among four packages, two on either side of the PCB. The chips themselves are IMFT's 32-layer, 256Gb stuff. The 256GB drive doesn't require enough of these dies for the controller to leverage significant interleaving over each of its four channels. We expect higher capacity SU900s to operate faster for this reason, even if Adata's specs don't suggest so.

Adata is bullish on the SU900's endurance, backing the 256GB drive with a five-year warranty and a 200 terabytes-written specification. Newegg is currently hocking the drive for $110, but Amazon will send the 256GB unit your way for an even hundo. Those prices may seem dear, but that's simply the state of the SSD market given the global NAND shortage. Competitors' products are no cheaper. Let's escape from our wallets' troubles by diving straight into testing.