Macintosh Memory Map — #8

Post #8 by techfury90

Source Forum	68kMLA
Category	68k
Post Date	Sun, 15 Jul 2012 - 08:49
Original URL	https://68kmla.org/bb/threads/macintosh-memory-map.25772/

Post

I'm curious about how memory mapping works on the Macintosh. On reset, the 68k loads from $000000, so the ROM must be there in some way when the machine boots. Some magic happens afterwards, and then when the system is running, the ROM is present in the address range $400000 - $41FFFF. How does this address translation work? What device provides that functionality? Any details would be appreciated. I'm learning about computer architecture, and this topic has me somewhat perplexed.

Just a heads up, the 68k does NOT start execution at $00000000. Instead, it loads the starting address at $00000000, then jumps to the address given there. The initial stack pointer is also given at $00000004 (also known as the A7 register).