Last modified: Fri Jun 19 19:50:29 UTC+0200 2026 © A. Tarpai

AMD64

AMD has won. Intel implements AMD 64-bit since then.

64-bit mode was made mainly so machine instructions can address more, than 4GB memory continuously using 64-bit addresses and 64-bit registers.

It is not another address space extension in the Intel sense! That is putting more address lines on the processor and using wider segment- (or page) bases. Even the 8086 or 286 could do this. But instructions itself until now could not address more, than 64KB/4GB in 16/32-bit mode.

Accompanied by code examples in tiny boot block files on GitHub:

• how to kick in 64-bit mode
• demonstrate 64-bit moves
• testing the new RIP-relative addressing mode
• and a heavy one: IDT-interrupts from 16/32/64-code in 64-bit mode