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Thread: Olivetti M21/M24 with BIOS version 1.44

  1. #1
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    Default Olivetti M21/M24 with BIOS version 1.44

    Hello, the newest BIOS version I know fpr M21/M24 is version 1.43. Now I see a pciture which shows a M21 with BIOS 1.44.

    https://www.ebay.de/itm/Olivetti-M21...wAAOSwtRNdgl5i

    s-l1600.jpg

    Anybody knows? Worth to try to get it? The seller is not that far from me, I can ask him if he could save it to a file. Which debug command would be necessary to get it?

  2. #2
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    I have never heard of 1.44, so like you, I'm very curious to see it! While I've written a nice utility to dump all option roms + the BIOS, I can't find it online right now, so you could point the seller to this: http://mess.redump.net/dumping/dump_bios_using_debug
    Offering a bounty for:
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

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    Have you tested, if that works for M21/M24? I think, M24 BIOS is 2x 2764, so it is 16 kB in total, but that instruction saves files of 8 kB length. The vendor agreed already to me to save the BIOS and forward the file to me.

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    The instructions I forwarded create a 64K file of the entire F000h segment, so it will grab anything that is there. Some relocation/trimming may be necessary afterwards.
    Offering a bounty for:
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  5. #5
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    Ah, Ok. So let's see.

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    Anybody here bought that M21? The vendor did not manage to read the BIOS with debug. So it's on you to do it.

  7. #7
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    I'd love to get my hands on a copy of this BIOS as well.

    I had an M21 as a kid, my dad brought it home from the car dealer he was working at the time. I recall it had a green phosphor CRT instead of amber most M21s seem to have. I also believe it was the system I played Space Quest 3 for the first time on.

    I'm not sure what ever happened to it, but I'd love to get my hands on another one someday.

    In any event, I'd like see this BIOS.

  8. #8
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    Cool

    The vendor now sent me the files, and in one of them I found the string "Resident Diagnostics Rev 1.44".

    m24_1.44.zip

    Please split into 2x files for 2764 EPROM and reattach to this posting, that everyone who wants to test, can do, And if you analyze, please tell us, what has been changed.

  9. #9
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    Excellent! The last 16K of file MYF800.BIN appears to contain the entire v1.44 BIOS and is indeed a little different looking than v1.43.

    I've extracted it to a single 16K binary as well as split into ODD/EVEN images suitable for burning to a pair of 8K EPROMS.

    I should get some time to test these in my 6300 this week but if anyone beats me to it, please report back whether or not these images work.

    BIOS_M24_144.ZIP

    Cheers!

  10. #10
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    Some obvious differences:

    1.43: 4/3/1986
    1.44: 5/5/1987

    The BIOS POST routine is slightly altered (it looks like the entire thing is different, until you realize it's just offset by about ~30 bytes; when you line that section up, most of it matches). In 10 minutes of looking, I see mostly just offset changes to new string locations. So what shifted it? The first major difference is at 11D6:

    Code:
    seg000:D1D4 B8 00 00                       mov     ax, 0
    seg000:D1D7 CD 40                          int     40h             ; Hard disk - Relocated Floppy Handler (original INT 13h)?
    seg000:D1D9 72 0F                          jb      short loc_FD1EA
    seg000:D1DB BB 00 7C                       mov     bx, 7C00h
    seg000:D1DE B8 01 02                       mov     ax, 201h
    seg000:D1E1 51                             push    cx
    seg000:D1E2 B9 01 00                       mov     cx, 1
    seg000:D1E5 CD 40                          int     40h             ; Hard disk - Relocated Floppy Handler (original INT 13h)?
    seg000:D1E7 59                             pop     cx
    I only have a commented disassembly of 1.00 so I can't match this up apples to apples, but it looks like these are redirected calls to the original INT 13h BIOS hard disk interrupt. If that's the case, this code is resetting the hard disk, then reading one sector into 7C00h, so this is definitely part of the boot process. But in 1.44, it looks like this:

    Code:
    seg000:0000 BB 00 7C                       mov     bx, 7C00h
    seg000:0003
    seg000:0003                loc_3:                                  ; CODE XREF: seg000:001Aj
    seg000:0003 33 C0                          xor     ax, ax
    seg000:0005 CD 13                          int     13h             ; DISK - RESET DISK SYSTEM
    seg000:0005                                                        ; DL = drive (if bit 7 is set both hard disks and floppy disks reset)
    seg000:0007 72 0C                          jb      short loc_15
    seg000:0009 B8 01 02                       mov     ax, 201h
    seg000:000C 51                             push    cx
    seg000:000D B9 0A 00                       mov     cx, 0Ah
    seg000:0010 CD 13                          int     13h             ; DISK - READ SECTORS INTO MEMORY
    seg000:0010                                                        ; AL = number of sectors to read, CH = track, CL = sector
    seg000:0010                                                        ; DH = head, DL = drive, ES:BX -> buffer to fill
    seg000:0010                                                        ; Return: CF set on error, AH = status, AL = number of sectors read
    seg000:0012 59                             pop     cx
    seg000:0013 73 3E                          jnb     short near ptr 53h
    seg000:0015
    seg000:0015                loc_15:                                 ; CODE XREF: seg000:0007j
    seg000:0015 80 FC 80                       cmp     ah, 80h
    seg000:0018 74 02                          jz      short loc_1C
    seg000:001A E2 E7                          loop    loc_3
    seg000:001C
    seg000:001C                loc_1C:                                 ; CODE XREF: seg000:0018j
    seg000:001C B2 80                          mov     dl, 80h
    seg000:001E 1E                             push    ds
    seg000:001F 2E 8E 1E 74 E5                 mov     ds, word ptr cs:0E574h
    seg000:0024 80 3E 75 00 00                 cmp     byte ptr ds:75h, 0
    seg000:0029 74 26                          jz      short near ptr 51h
    Still part of the boot process (loading to 7C00h), but more more int 13h->40h redirection. So this tells me that the 1.44 BIOS's major changes were rewriting the disk routines somewhat. I don't know why the 1.44 BIOS is reading sector 0A instead of sector 01 though.
    Offering a bounty for:
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

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