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stepleton

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  1. stepleton

    GEMDOS on the Lisa can be built again!

    did somebody say VIA addresses? For your reference: https://github.com/stepleton/lisa_io/blob/master/lisa_profile_io.x68#L149
  2. stepleton

    GEMDOS on the Lisa can be built again!

    *waves arms* I'll take one!
  3. stepleton

    GEMDOS on the Lisa can be built again!

    Wow!! Once you have this up and running, GEMDOS will be one of the few Lisa OSs for which we have source code. The only other one out there for now that I know of is the Lisa Monitor, an Apple-internal OS that supported development of the Lisa OS, the Office System, and its apps. There are scans of a printed listing on Bitsavers.
  4. stepleton

    GEMDOS on the Lisa can be built again!

    Woohoo, congratulations!! I'm glad someone found a use for that I/O library. I had a practical use in mind --- still do --- but I keep getting distracted by other projects! Any benefit you may have enjoyed from my code as a learning tool comes from repackaging the knowledge that has been reverse-engineered or archived by other people --- I'm thinking of things like bitsavers, Patrick Schaefer's website, LisaEm, the BLU documentation, the list goes on... Can't wait to see GEM going---good luck!
  5. stepleton

    GEMDOS on the Lisa can be built again!

    Super minor point here, and you may have spotted it already, but there's a dropped zero---the boot block is loaded to $20000. Look for the symbol "TWGDATA" in the boot ROM: http://bitsavers.trailing-edge.com/pdf/apple/lisa/firmware/Lisa_Boot_ROM_Asm_Listing.TEXT
  6. stepleton

    GEMDOS on the Lisa can be built again!

    It might be useful to try out the cross-compiler just to help troubleshoot the problem. Good luck! I don't know much about GEMDOS, but I'm cheering for this project as a spectator Quick question---I suspect the answer is no, but does GEMDOS use the Lisa's MMU in any way? I'm guessing not (it probably just uses the flat memory space set up by the boot ROM), but if it does use the MMU, then it's possible that any old 68k compiler won't work. The 68000 can only recover from a page fault for certain instructions, so subroutine calls have to generate code that uses these instructions to "test" distant memory locations (and thereby trigger a page fault) before doing any actual work with them.
  7. stepleton

    A Bit Of A Rarity

    Thanks for doing this. I can't really understate how much I've gained from all of the materials the community has shared on outlets like Bitsavers, Macintosh Garden, the Internet Archive, and so on. I always try to pay it forward with stuff from my own collection.
  8. stepleton

    A Bit Of A Rarity

    Mac Twiggy drives have a different connector altogether---20 pins as opposed to 26 or so. It's possible you could work up an adaptor, but I wouldn't volunteer to do it for you . Another possibility would be to swap the digital board (lower board) on the drive for a digital board from a Lisa Twiggy drive, then stick the resulting Frankenstein into the Lisa. Here too I would explore other options first. There is a Twiggy expert in the UK who would be thrilled I think for the chance to learn about the Mac drive specifically. He's been studying Twiggy drives for a long time and is probably a good person to know in your quest to put the drive in working order (assuming it is not in working order already). I'll point him at this thread.
  9. stepleton

    A Bit Of A Rarity

    I have a Lisa 1 and have advertised on 68kmla before about my enthusiasm for helping people back up old disks. I will gladly do this for free for anyone with a disk in a condition that's unlikely to damage my drives. Unless there's something unique about the geometry of Mac prototype Twiggy drives, which I suspect is unlikely (but have no idea either way), backup via BLU is likely to work for a disk in fair condition. That said, I live in the UK and any overseas shipping would have to be considered very carefully! There are probably other recovery options to consider first. Still, my Lisa 1 is at your service. Thus far Twiggy drive belts appear to be fairly robust. (At least something about the drive is robust!) Mine are the originals as well, and I've heard at least one other Lisa 1 owner reporting the same.
  10. stepleton

    GEMDOS on the Lisa can be built again!

    Do whatever will be the most fun for you, is what I'd say Personally, as long as it doesn't stop anyone from doing the historical stuff later, I'm always a fan of more features and capability...
  11. stepleton

    GEMDOS on the Lisa can be built again!

    Oh wow, that's fantastic! I'm so happy my library was useful for, well, anything at all really I had considered mentioning it here, but as it's written to be small, I didn't think it would be so helpful for explaining how Apple parallel port drives work. I didn't consider that you would just cut the knot with it instead! Is the PPP(xxxx)RRR/WWW part of the GEMDOS code or is it some debugging text that you've added while you were integrating the library? Can't wait to see what you do next...
  12. stepleton

    Apple Lisa Twiggy/FileWare Disk Recreation

    I've only ever used DS/HD disks in my Twiggies. My first hacked up disk (which once held a portion of Microsoft BASIC Professional Development System 7.1) has been holding good bits since 1998. Other brands have done okay; I think usually 3M has been the best, but I've never been too picky---I've been slowly working through floppies I've found at junk stores and assuming around a 50% success rate. Other than the slight 3M preference, I haven't made enough disks to notice consistent patterns among brands. I think most of the success is down to how much I bend the disk jacket while I'm cutting it up. I tend to trust James MacPhail a lot, but the good news is that we don't have to take his word for it . The Twiggy specifications document on Bitsavers, PDF page 78 (at top), specifies a coercivity of 600 oersteds. This is identical to DS/HD media per Wikipedia or this old Byte article. DS/DD media is 300 oersteds.
  13. stepleton

    GEMDOS on the Lisa can be built again!

    Huh, interesting! Not certain how sure you are of reading working, but as a test, you might try reading block $FFFFFF, which is the spare table for the ProFile---if the first 13 bytes are 'PROFILE ' (note six spaces), then you're probably reading valid data. (Then again, if the GEMDOS disk driver really expects sectors to have only 512 bytes, then it might be ignoring the first 20 bytes of the 532-byte block, so if it doesn't work, it doesn't necessarily mean things are broken.) Writing is not so different from reading, so even if there's a bug, I expect most of the hard work will have been done already.
  14. stepleton

    GEMDOS on the Lisa can be built again!

    Wow, congratulations! I'd love to have the files. Is there any support for hard drives, or is it floppy-only?
  15. stepleton

    Lisa "mouse missing" notification

    The hardware reference manual is a good resource in general. A later version can be found at Ray Arachelian's site. The COP421 firmware was cunningly extracted from the chip by Patrick Schaefer a few years ago. You can find it on Bitsavers, but although the firmware has been disassembled, there's no commentary. You can read more about how Patrick did the extraction on his website -- it's pretty impressive!
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