NPX(4)

💅 NPX(4) — Numeric Processing Extension coprocessor 💅

okay so bestie, this page is from the i386 Kernel Interfaces Manual, and we're talking about npx, the Numeric Processing Extension coprocessor ✨

🎀 NAME 🎀

npx — Numeric Processing Extension coprocessor 💖

✨ SYNOPSIS ✨

device npx
hint.npx.0.at="nexus"
hint.npx.0.port="0x0F0"
hint.npx.0.flags="0x0"
hint.npx.0.irq="13"

🌸 DESCRIPTION 🌸

The npx driver is the glow-up that lets your system actually use its Numeric Processing Extension coprocessor 🧚. Numeric processing extensions are present in systems with 486DX CPUs and in systems with 387 or 487SX coprocessors — periodt 💅. The npx driver is required for proper system functioning; if there is no NPX in the system, the system will not boot. Not me being dramatic, it's literally in the man page 😭.

The flags for npx0 are:

• 0x01 — do not use the NPX registers to optimize bcopy 🦋
• 0x02 — do not use the NPX registers to optimize bzero 🎀
• 0x04 — do not use the NPX registers to optimize copyin or copyout 💜

The NPX registers are normally used to optimize copying and zeroing when all of the following conditions are satisfied:

1. cpu I586_CPU is an option ⭐
2. the CPU is an i586 (perhaps not a Pentium) 👑
3. the probe for npx0 succeeds 🔥
4. INT 16 exception handling works ✅

Then copying and zeroing using the NPX registers is normally 30-100% faster — highkey iconic 🚀.

The flags can be used to control cases where it does not work or is slower. Setting them at boot time using hints works correctly (the optimizations are not used until later in the bootstrap when npx0 is attached). This is the "set it early, bestie" situation 🫶.

💀 BUGS 💀

There are lots of them, especially on old cheap motherboards 😬. In particular, some motherboards do not have the interrupt lines from the NPX to the CPU wired properly. So like... check your wiring, or at least know that's a thing 🫠.

xoxo, your Debian bestie 💅 — August 28, 1993 🎀