ACTHD: 0xffffffff
EIR: 0x00000000
EMR: 0xfffffffd
ESR: 0x00000011
PGTBL_ER: 0x00000002
IPEHR: 0x01000000
IPEIR: 0x00000000
INSTDONE: 0x7dffffc0
    busy: Framebuffer Compression
Ringbuffer: Reminder: head pointer is GPU read, tail pointer is CPU write