PORTIBM PC Portable (uses same BIOS as XT) 00F0-00FF - MATH COPROCESSOR (8087..80387) 00F0 -W math coprocessor clear busy latch (write 00h) 00F1 -W math coprocessor reset (write 00h) 00F8 RW opcode transfer (CPU-coprocessor communication) 00FA RW opcode transfer 00FC RW opcode transfer