5 ms·
AIUI, the main difference is that memory locations $0000 and $0001 are used for the 6510 i/o port. So dropping a 6510 in a system that makes use of those perfe
by ksherlock 3y ago
AIUI, the main difference is that memory locations $0000 and $0001 are used for the 6510 i/o port. So dropping a 6510 in a system that makes use of those perfectly valid memory locations won't work either.
- dusted 3y agoindeed, the ports at 00 and 01 and that pin 5 could be pullsed low by external logic to have the 6510 tristate it's bus pins so external logic could control the bus, this was used by the VIC2 chip in the C64.
- systems_glitch 3y agoSame issues with e.g. the Rockwell R6500 single-chip microcomputer family -- the actual microcontrollers, not their second-source MOS 6500 family chips. Rockwell put I/O stuff and stack both in zero page to make more efficient use of limited ROM space, and allow operation with only the tiny amount of on-chip RAM! A lot of stuff can be restructured to live with it, but almost nothing "just works."