HelenOS sources

search_rsdp       195 kernel/genarch/src/acpi/acpi.c 		rsdp = search_rsdp((uint8_t *) PA2KA(ebda), 1024);
search_rsdp       198 kernel/genarch/src/acpi/acpi.c 		rsdp = search_rsdp((uint8_t *) PA2KA(0xe0000), 128 * 1024);
HelenOS homepage, sources at GitHub