From someone: To connect the cpus, GMCHTapController instruction 0xa must be written into the instruction register, after this the cpus are connected to the jtag chain (make sure the treset pin is at logic level high!): tdi->GMCHTapController->CPU1->CPU0->tdo Cpus instruction register length is 7 bits, idcode instruction is 0x2 For example to read the idcode of the first cpu write 20 bits 0xfff82 into the instruction register, read 34 bits from the data register and consider the lower 32 |