Author: ray (rn043.isis.de)
Date: 06-20-2003 20:39
hiya,
>Only using 24bits of the address bus also made the falcon more compatible - an address points to the same piece
>of memory on an ST as it does on a Falcon. If the falcon used all 32 bits, then ST memory addresses would
>actually be "mirrored" in every 16meg chunk of Falcon memory = mess if compatibility is a priority.
>I think that's right? anyone know better?
i'm pretty sure the falcon used the 030's full 32bit address bus to address its memory...how could you be able to access tt/fast ram above that 14mb (16mb including rom, memory mapped hw.) limit on that machine otherwise.
something else which i'm 100% sure about:
atari used the 030's onchip PMMU to mirror the ST's $00ffxxxx address space into
the falcon's/TT's upper block of memory ($ffffxxxx) in order to achieve downward-compatibility to applications using the absolute short addressing-mode ($xxxx.w) in order to access those addresses.
