New computers don't speed up old code
Why Hacker News recommends it
Used as evidence that CPU speed for branchy, dependent code has improved only modestly in 15-20 years, so software optimization matters.
What it is
Matthias Wandel tests old and new code on a range of PCs, including a new mini PC, to measure how much faster modern hardware really is. He also shows optimization techniques such as branchless code, with benchmark programs on GitHub.
Recommended by 3 HN commenters across 3 different months, 2025 to 2025.
What Hacker News said
Strong rec MontyCarloHall · 2025-09 · on “The Weird Concept of Branchless Programming”
This great video [0] demonstrates how CPU performance has only increased 1.5-2x over the past 15(!) years when executing extremely branchy code. Really shows you just how deep modern CPU pipelines have become. The video also showcases a much more impressive branchless speedup: computing CRC checksums. Doing this naïvely with an if-statement for each bit is ~10x slower than doing it branchless with a single bitwise operation for each bit. The author of the article should consider showcasing this too, since it's a lot more impressive than the measly 1.2x speedup highlighted in the article. I assume the minimal/nonexistent speedups in the article are due to modern CPU branch prediction being qu
Recommends dijit · 2025-05 · on “The world could run on older hardware if software optimization was a priority”
Maybe since 1980. I recently watched a video that can be summarised quite simply as: "Computers today aren't that much faster than the computers of 20 years ago, unless you specifically code for them". [this video] It's a little bit ham-fisted, as the author was shirking decades of compile optimisations also , and it's not apples to apples as he's comparing desktop class hardware with what is essentially laptop hardware; but it's also interesting to see that a lot of the performance gains really weren't that great actually. he observes a doubling of performance in 15 years! Truth be told most people use laptops now, and truth be told 20 years ago most people used desktops, so it's not totally unf
Recommends torginus · 2025-08 · on “Uncle Sam shouldn't own Intel stock”
Watch this video: [this video] New computers aren't as much faster as benchmarks would lead you to believe. If your code relies on unpredictable branches, dependept memory accesses in a tight loop, or very tight feedback loops inside computations, new CPUs won't have that much of an edge.
Cites scotty79 · 2025-05 · on “The world could run on older hardware if software optimization was a priority”
Since 1980 maybe. But since 2005 it increased maybe 5x and even that's generous. And that's half of the time that passed and two decades. [this video]