80386 Multiplication and Division
owl writes:
https://nand2mario.github.io/posts/2026/80386_multiplication_and_division/
When Intel released the 80386 in October 1985, it marked a watershed moment for personal computing. The 386 was the first 32-bit x86 processor, increasing the register width from 16 to 32 bits and vastly expanding the address space compared to its predecessors. This wasn't just an incremental upgrade-it was the foundation that would carry the PC architecture for decades to come.
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In addition to its architectural advances, the 386 delivered a major jump in arithmetic performance. On the earlier 8086, multiplication and division were slow - 16-bit multiplication typically required 120-130 cycles, with division taking even longer at over 150 cycles. The 286 significantly improved on this by introducing faster microcode routines and modest hardware enhancements.
The 386 pushed performance further with dedicated hardware that processes multiplication and division at the rate of one bit per cycle, combined with a native 32-bit datapath width. The microcode still orchestrates the operation, but the heavy lifting happens in specialized datapath logic that advances every cycle.
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