On Wed, 3 Jan 2007, Dave Dunfield wrote: I've extracted the first of the two Exec ROS', the one containing all the monitor and I/O routines. I'm in the progress of disassembling and commenting the code. I've also disassembled several IBM utility programs, e.g. TDTCOPY, DDCOPY, SIO8BIT, DIAG DCP and so on. This for example is the beginning of the Tape I/O supervisor routine: ; *************************** ; Device E (Tape) I/O Routine ; *************************** 7F00 216C MOVE R1, $D8 ; Vector table for I/O routines 7F02 A13B ADD R1, #$3C ; Vector to device F 7F04 D718 MOVE R7, (R1) 7F06 0F33 INC2 R15, R3 7F08 6EF0 MOVB R14, (R15)+ ; IOCB_Cmd 7F0A 6DF6 MOVB R13, (R15)--- ; IOCB_Flags 7F0C CE0B SNZ R14 7F0E A00B BRA $7F1C ; "Sense" command 7F10 8C30 LBI R12, #$30 7F12 8103 LBI R1, #$03 7F14 CE10 SLE R14, R1 ; Read or Write ? 7F16 A007 BRA $7F20 ; No 7F18 CDC6 SBC R13, R12 7F1A A02B BRA $7F48 ; Bit 2 or 3 set 7F1C 2807 MOVE R8, $0E ; R7L0, contains vector 7F1E 2056 JMP ($00AC) ; Do I/O and return to caller [...] Yes. The 5110 can only access the following ROS': Common ROS BASIC ROS APL ROS and maybe Diskette Sort (haven't tried yet) These ROS' are accessed as an I/O device. You write two PUTB instructions to device 1, MSB of the ROS address first, then LSB. Then you can read the contents of this ROS with consecutive GETBs (the second GETB automatically increments the ROS address by 1; ROS address is given as word address!). I've read these ROS' from my 5110 model 1. The Executable ROS is only accessible by the processor during an instruction fetch cycle... and by the graphics adapter while -POR is active! BTW I haven't found any 360 / S/3 emulator yet. Both BASIC and APL ROS don't contain any code I recognize. Really? Until now nobody have had any interest in neither a Kermit for the 5110 nor an Infocom interpreter (both written in assembly). Of what non-executable ROS? There are several. Do you also have the Diskette Sort feature (additional ROS card)? You haven't searched for that information, have you? Do you know my site? It's still not complete, though, as I'm learing more and more while disassembling programs and playing with different bits... Christian