You should have RS232 on the machine. Thats going to be the fastest. Even though a BTR might handle 19200 buad, the old tape readers could not, so it will still bottleneck feeding in to the actual control. Your major downfall on that machine is the block to block speed on processing, no way around that that I know of. Although, if the machine still has bubble memory in it, I have found data transfer rates slightly faster with the new Sram board from fanuc. About a 1500.00 board.