MPCPIC_IVEC
openpic_write(MPCPIC_IVEC(irq), OPENPIC_IMASK);
openpic_write(MPCPIC_IVEC(irq), x);
x = openpic_read(MPCPIC_IVEC(irq));
openpic_write(MPCPIC_IVEC(irq), x);
x = openpic_read(MPCPIC_IVEC(irq));
openpic_write(MPCPIC_IVEC(irq), x);