On the Zilog Z80, executing DI (disable interrupts) followed by HALT (wait for an interrupt) results in the CPU staying frozen indefinitely, waiting for an interrupt that cannot happen. The similar Sharp processor core in the Game Boy's LR35902 system on chip contains a partial fix allowing it to recover from one HALT, like the 65C02's analogous WAI instruction, but it becomes frozen with three consecutive HALTs with interrupts disabled. The core itself contains no less than 11 opcodes that fully lock the CPU when executed.