THE 386 — a dart

THE 386 32 bits, and the permutation that stuck — IA-32, four gigabytes

The 80386 (1985) is where the x86 permutation truly landed: full 32-bit registers and a flat 4GB address space (2₃₂ = 4,294,967,296 bytes), while still booting as an 8086 and able to run 16-bit code in a virtual-8086 sub-mode. This is IA-32, the architecture that ran the PC world for two decades. Where the 65816 line stopped at 16-bit, the 386 doubled again and kept the whole past reachable underneath — the permutation that stuck, and the direct ancestor of the 64-bit machine you are reading this on.

THE TECHNIQUE 32-bit registers, 4GB flat address space — IA-32

The demo shows the 32-bit register maximum (0xFFFFFFFF) and the 4GB address space it spans: live demo

HISTORY & CREDIT Intel 80386 · 1985 (IA-32)

“The 16-bit era just ended.” — the 386 doubled to 32-bit while keeping every earlier mode reachable underneath. cited

the width · 32-bit registers; a flat 4GB address space (2₃₂ bytes).
the compatibility · boots as an 8086; virtual-8086 mode runs old 16-bit code.
1985 · Intel 80386 — IA-32, the architecture that ran the PC for twenty years.

The word doubled to thirty-two and the whole past kept underneath — the permutation that stuck. 32-bit

RECOMMEND FOR I-13 the 32-bit max, on the compiler

On the canonical compiler, a 32-bit register maxes at 4,294,967,295 and the address space is 4GB:

$ i13 run ln_386.i13 # 32-bit width RUN OK · 14 step(s) · peak stack 3 · call depth 0 reg32_max = 4294967295 -- 0xFFFFFFFF gb4 = 4294967296 -- 4GB address space is_32bit = 1

Recommend as a NULL — a width doubling, i.e. representation + resource. The 386 widens the register/address to 32 bits: a representation change (B44) buying more range/memory (B40), the earlier modes spec-preserved (B39). No new invariant. NULL — but the historically decisive one: the permutation that stuck and led to the machine running this page.