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Calling All Hands - Yamaha C1 Laptop Expansion Slot

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    Calling All Hands - Yamaha C1 Laptop Expansion Slot

    I've received a very interesting memo about the Yamaha C1 Music Computer.

    This machine had 8 MIDI slots and a special version of Sequencer Gold to use them all. Supplied with either 20MB MFM HDD and a floppy or two floppies.

    Needless to say the challenge is to get a CompactFlash storage board made for this machine. It has an expansion slot and that is specifically what I need help finding data on - physical dimensions, connector type and pin out, everything basically.

    All help on this greatly appreciated. This project is quite exciting because there is a real use case coming out of this

    Another BT adventure, I presume?

    Ethan O'Toole mentions having documented the expansion pinout on his blog. Might be worth reaching out to him for that information.

    Otherwise, you'll probably need to purchase the service manual.


      Awesome thanks for the links! I wonder how detailed the service manual is. A schematic would be perfect.


        Originally posted by pearce_jj View Post
        Awesome thanks for the links! I wonder how detailed the service manual is. A schematic would be perfect.
        I bought the SM so it can be shipped quicker to a US address. They didn't offer expedited shipping. But anything would be quicker than to the UK.

        When it arrives, I'll scan it in and send it to you electronically. I can send it along in the post later if you want. I think I still have your mailing address here somewhere.

        Consider it a donation to 'the cause'.
        "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me


          That’s so super awesome, thank you! Scan would be brilliant


            With the very kind help of eeguru, the tech ref is now in hand

            Looks like the built-in HDD interface is *very nearly* IDE - everything we need electrically is there to interface to CompactFlash directly.

            The system ROM is apparently 64KB. I don't yet know if there is any free space in it or any available ROM sockets.

            Next step will be to look at these. The only challenge I think will be patching out the built-in HDD code and getting the XTIDE Universal BIOS stored somewhere and initialised.


              Here is the HDD Interface pinout:

              Screenshot 2019-01-05 at 20.49.48.jpg


                I've attached the system BIOS. Others have reported that Type 47 is not available in the interface but it is in the text list in the BIOS.

                We need to modify the BIOS by either:

                1. Adding XTIDE UB for generic 16-bit IDE controller at 1F0h in unused space (8K offset appears to be clear) and patching the BIOS to call it; or
                2. Patching the existing BIOS to enable type-47 selection.

                Any help on this greatly appreciated! Other than that a simple patch PCB to isolate unused signal wires (like motor run) is all that's needed on this
                Attached Files


                  James, I'm looking into patching XUB into the system BIOS but can't make any promises as to when or if it will be done. Just wanted you to know I'm giving it a shot.
                  Looking for a cache card for the "ICL ErgoPRO C4/66d V"


                    That would be so awesome Antilles, thank you!


                      Autocorrect LOL


                        I've disassembled the system BIOS completely and found more than enough free space, so any build of XUB can be patched in. My plan is to patch it in at offset 4000h. The option ROM scan stops at segment F000h so I will have to extend that, then adjust the checksum and it should be good to go. I'm thinking that the Large AT build should be OK to use? I will also configure it to use a single standard 16-bit ISA IDE controller at 1F0h, not using any IRQ (for max performance).

                        Does this sound OK?
                        Looking for a cache card for the "ICL ErgoPRO C4/66d V"


                          All spot on.

                          If you can pull this off that will be super amazing!


                            Can you see the built in code scanning 1F0h btw? Ideally we’d patch that out or perhaps we don’t need to?


                              Originally posted by pearce_jj View Post
                              Can you see the built in code scanning 1F0h btw? Ideally we’d patch that out or perhaps we don’t need to?
                              We shouldn't need to do that. I'm assuming that the system BIOS can be configured to have no harddrives? Do you have access to this machine for testing, BTW?

                              Anyway, I've patched in the Large AT build of XUB r600+* beginning at offset 4000h and ending at offset 67FFh. At offset 6800h I've changed the byte there from FFh to F9h to offset the change I did when extending the option ROM scan to segment F600h. The thing is, I can't find any code that checks for a valid checksum of the system BIOS so this might not be needed. The change I did to extend the option ROM scan is at offset 8D8Eh.

                              I've attached a zip file with;
                              the IDA database file containing the disassembly,
                              BEFORE.BIN which is the first part of the original binary up to offset 3FFFh,
                              FF.BIN which is just the part of the original system BIOS that is replaced by XUB,
                              the XUB binary configured as I said above
                              and AFTER.BIN that is the part that comes after XUB.

                              Note that I have not patched AFTER.BIN to include the option ROM scan extension or the checksum byte so you can do
                              copy/b BEFORE.BIN+FF.BIN+AFTER.BIN SYSTEM.BIN
                              to get a copy of the original BIOS in SYSTEM.BIN.

                              The included C1ROMXUB.BIN is the complete BIOS patched and ready to go (I hope)!

                              The zip file had to be split into two parts so I could attach it to this post, just do a
                              copy/b C1ROMXUB.ZIP

                              * r600+ meaning some small changes I've done that will be added to the repository on my next commit.
                              Looking for a cache card for the "ICL ErgoPRO C4/66d V"