GPX_ADDER_OFFSET
ioaccess(tmp, vax_trunc_page(GPXADDR + GPX_ADDER_OFFSET), 1);
ioaccess(virtual_avail, GPXADDR + GPX_ADDER_OFFSET, 1);
vax_map_physmem(va->va_paddr + GPX_ADDER_OFFSET, 1);
GPX_ADDER_OFFSET, 1);
GPX_ADDER_OFFSET, 1);