Sequential vs 4K Scores: Which Row Actually Matches Daily Use?
Every drive advertises its sequential speed, and AS SSD Benchmark prints it in the first row — so it is natural to treat the Seq row as the verdict. It is not. The sequential test streams one large file from end to end, a pattern your computer almost never produces outside of copying a movie or an ISO image. The 4K rows measure something much closer to your actual day. This page explains the difference, why the benchmark’s own scoring sides with 4K, and shows a published head-to-head in which the drive with the lower sequential speed won the total score comfortably. To see your own rows, run the tool from our download page.
What sequential speed measures — and when it matters
The Seq test reads and writes a 1 GB file in one continuous stream. Nothing interrupts it, nothing competes with it, and the drive can run its flash channels flat out. That is a real capability, and it governs real tasks: copying large files, capturing video, unpacking big archives, installing games from a local image. If your work is moving large media files, the Seq row deserves your attention. But notice how narrow that list is. Booting Windows, launching applications, loading game levels, compiling code, browsing — none of these stream one file end to end. They issue thousands of small, scattered requests, which is a different test entirely.
What the 4K rows measure
The 4K row reads and writes randomly placed 4 KB blocks, one at a time — the access pattern of an operating system pulling in libraries, registry entries, fonts, thumbnails and application data from all over the drive. The 4K-64Thrd row runs the same pattern with 64 threads queued at once, modelling a busy system with many programs active together. Both rows are bottlenecked by latency and by how efficiently the controller handles small requests, not by raw link bandwidth. That is why their numbers look tiny next to the Seq row, and why they vary so much between drives that share identical sequential ratings. Our guide to reading the results grid covers each row in context.
The scoring formula already picked a side
You do not have to take our word for which row matters — the benchmark’s author encoded the answer in the score formula. In the simplified published form, sequential speed is multiplied by 0.1 before it counts, while the 4K and 4K-64Thrd results count at full value. A drive must therefore be ten times faster sequentially to gain what a modest 4K improvement delivers. The total score is, by design, mostly a random-performance score with a sequential garnish. When two drives’ totals surprise you, the explanation is almost always sitting in their 4K rows.
Proof from published results: the slower-Seq drive that won
Legit Reviews’ archive contains a near-perfect natural experiment. The Intel Optane SSD 800P 118 GB (AS SSD 2.0.6485.19676) posted sequential speeds of 1,335.90 MB/s read and 611.58 MB/s write — unremarkable numbers, lower in both directions than many ordinary drives. But its 4K results were 152.75 MB/s read and 129.01 MB/s write, far beyond what NAND-based drives typically manage in that row, and its total came to 3,309. Compare the Samsung SM951 512 GB (tested with AS SSD 1.7.4739.38088, so its total is not on the same version scale — compare its rows, not its score): sequential speeds of 1,988 MB/s read and 1,510 MB/s write, roughly 49% faster reading and two and a half times faster writing than the Optane drive, but a 4K read of just 45 MB/s against the Optane’s 152.75 MB/s. The Optane drive was built for low-latency small-block work, and in the row that models daily use it was more than three times faster — while losing the headline row badly. Anyone who had ranked these two drives by their Seq numbers alone would have ranked them backwards for desktop responsiveness.
How to weight the rows for your own use
Match the row to the workload. General desktop, office and gaming: read the 4K row first, then 4K-64Thrd, and treat Seq as background information. Video editing, large backups, file-server duty: the Seq row and the Copy-Benchmark’s ISO scenario (see Copy-Benchmark explained) become genuinely important, because sustained streaming is your actual workload. Mixed or unknown use: the total score is a reasonable shorthand precisely because it is 4K-weighted — but glance at the rows anyway, since a total can hide one collapsing row behind two strong ones. And in every case, compare only against results from the same AS SSD version and test size, ideally a professional review of your exact drive, as set out in what is a good AS SSD score. The Seq row is the loudest number on the screen. The 4K rows are the honest ones.
One more place the same lesson hides
The Copy-Benchmark tells the same story in plain language. Its ISO scenario — two large files — is a sequential workload, and it is always the fastest of the three. Its Program scenario — a folder full of small files — is a random workload wearing a copy dialog, and it is always the slowest, on every drive, by a wide margin. Legit Reviews’ figures for the Crucial BX200 make the point concretely: 486 MB/s in the ISO test against 323 MB/s in the Program test, from the same drive in the same minute. Nothing about the drive changed between those two runs; only the shape of the work changed. Your operating system spends its day shaped like the Program test, not the ISO test — which is the whole argument of this page in a single pair of numbers.