3 ms·
This happens all the time. Early MacOS put flags in the upper byte of heap pointers, because somebody thought “16MB is enough for anybody”. Physical address ext
by wrs 2y ago
This happens all the time. Early MacOS put flags in the upper byte of heap pointers, because somebody thought “16MB is enough for anybody”. Physical address extensions had to be added to 32-bit Intel because 4GB turned out to not be “enough for anybody”. Now “64-bit” processors today have 48-bit physical address spaces (or less), but we’ll see…
- rvense 2y agoWell, as you probably know, the first Mac shipped with a 68000 that didn't have the full 32 bit physical address space either, so that upper byte was basically free real estate. (The original Mac hardware is in many ways a masterpiece if you like tricks like this.)
- wrs 2y agoIndeed, but I didn't count Motorola's decision there as "24 bits is enough for anybody", because they didn't break anything in the 68000 when they added more bits to the address space (in other words, it was forward-compatible). It was the Heap Manager that broke!