Not sure what hardware is responsible for this, probably that funky MMU chip. Commodore 128 will halt the non-active CPU (Z80 or 8502). The NES halts the CPU when it tells the PPU to DMA 256 bytes of memory to sprite descriptor memory before it renders the frame. ![]() The video chip on the Commodore 64 halts the CPU during the frame to fetch memory every 8 lines IIRC (disabling video output increases CPU speed by a bit) IMHO I think for older classic CPUs in embedded situations, the expectation was that if halting the CPU was needed, external logic would do that. Interesting fact: The TMS9900 had an IDLE instruction - I recall reading somewhere that it was implemented internally as an unconditional jump to itself.
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