You are staring at a loading spinner. Again. Your machine can execute billions of instructions per second, yet you’re watching a tiny circle orbit itself. It has been this way for years. More power, same waiting. And that’s not just a coincidence — it’s a design.
\n\n
Deep inside your CPU, there are instructions so slow, so pathological, that they can turn a 5 GHz flagship into a pocket calculator. Not by doing something complex. By doing something trivial — in exactly the wrong way.
\n\n
A developer called xoreaxeaxeax collected these monsters in a GitHub repo called the Assembly Hall of Shame. It’s a list of x86 instructions that take thousands of cycles, not because they’re difficult, but because they trip hidden wires in the hardware. This sounds like curiosity. It’s really a weapon.
\n\n
When you try to make a computer as slow as possible, you learn more about it than when you try to make it fast.
\n\n
Here’s the trick: many of these instructions use floating-point subnormals. These are numbers so tiny they sit in the wilderness of the IEEE 754 spec. The hardware doesn’t handle them gracefully. Instead of a quick calculation, the CPU enters a microcode loop that can stall for hundreds of cycles. One instruction. A wrong number. A machine that chokes because of a rounding artifact.
\n\n
Other instructions play with MMIO — memory-mapped I/O. They force the CPU to talk to a peripheral over a slow bus, and if you target the wrong memory address, the processor waits. And waits. And waits. The instruction set is supposed to be deterministic, but the hardware is built on negotiations, edge cases, and ancient compromises.
\n\n
The beautiful, terrifying irony? By every benchmark, modern CPUs are absurdly powerful. And yet a single line of assembly can make that power vanish.
\n\n
Abstractions exist to hide complexity. But when you pull the curtain, the complexity isn’t just ugly — it’s sometimes deliberately hostile.
\n\n
The commenters on the Hall of Shame can’t help but joke. One of them concluded: \”we should be using the nop instruction for everything.\” They’re being sarcastic, but they’re also onto something. The instructions that do nothing are the only ones you can trust. Everything else is a potential trap.
\n\n
And that trap is the point. xoreaxeaxeax didn’t stop with this list. They made a compiler that emits only mov instructions — because you can build anything with just moves. They made another that sabotages fake disassemblers by drawing skulls and threats in the reversed code. This isn’t trolling. It’s adversarial engineering, and it’s one of the most honest forms of education we have.
\n\n
Think about it: you can spend years learning how to write faster code. Or you can spend a week learning why code becomes slow, and in that week, the entire mental model of your CPU flips inside out. The edge cases that plague the Hall of Shame are the same edge cases that hide inside the \”normal\” corners of every program.
\n\n
The worst instructions in the world aren’t useless. They’re the most honest part of your CPU. They tell you what the hardware actually fears.
\n\n
Your computer feels slow because it is — but not in the way you thought. It’s not that the processor isn’t fast enough. It’s that the processor is constantly dancing on a minefield of its own design. The next time your cursor freezes, remember: somewhere in that silicon, a subnormal just triggered a microcode panic. And somewhere in a GitHub repo, someone is smiling.
\n\n
Study the shame. Because what makes a computer slow is exactly what makes it complicated. And what makes it complicated is exactly what makes it worth understanding.
FAQ
Q: What is the key takeaway?
A: See the article.