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Thread: Drive parameters for Gotek USB disk

  1. #1

    Default Drive parameters for Gotek USB disk

    Iím waiting for the arrival of a GoteK SFR1M44-U100K USB drive from China

    http://www.gotekemulator.com/

    It will replace the 5.25Ē drive that has long gone. As the Gotek can be used in 720Kb, 1.2Mb or 1.4 Mb mode Iíve been looking at the modifications to be made to the Disk tables in my CP/M 2.2 setup.

    I have interfaces and tables for a Hard drive, 8Ē floppy and 5.25Ē floppy and have been reading the CP/M alteration guide and looking at my BDOS listings from 30 plus years ago and am unable to reconcile some of the decisions I made back then. Iím prepared to accept they could well be wrong in some small way (the disks worked, or appeared too).

    In the past I had copies of floppy disks with everything on and hacking about didnít cost anything if errors were made. With my only source being on an ancient 10Mb hard drive I have to get it right first time what is more I canít use DISKDEF and compile it to get the values. I plan to read in the BDOS into memory, patch the existing table parameters for the 5.25Ē disks and copy the hard drive. I can then mess with things without risk.

    It would be nice to know the how each of the parameters in the Disk Parameter Header, Disk Parameter Block relate, and how they are calculated. So is anybody aware of a good explanation of the table values and how they are derived? Have a spreadsheet that can be used to get the values that DISKDEF would have generated? Have an example of the tables for a Gotek in any of its 3 formats.

    Regards

    Pete

  2. #2

    Default

    You are talking about a soft sectored 5.25 disk?
    Is the hard disk a MFM disk and what is the controller? Why does it have to work on the first shot. Why not disconnect the hard drive and just boot from a working floppy first and then look at the hard disk? Who's Gotek software are you using?
    Dwight

  3. #3
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    Default

    If you're planning to use the Gotek with its out-of-the-box firmware I'd strongly recommend against it, it really is garbage. The free option for upgrading it is Flashfloppy:

    https://github.com/keirf/FlashFloppy

    You can also buy a special version of the HxC firmware for Gotek hardware:

    http://hxc2001.free.fr/floppy_drive_...rmwareForGotek

    Either of these is probably a much better option for working with a CP/M machine because they can directly support many standard emulator disk formats. The raw Gotek firmware is mostly hardwired to only support MS-DOS-like floppy formats and it doesn't do that particularly well.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  4. #4

    Default

    Quote Originally Posted by Dwight Elvey View Post
    You are talking about a soft sectored 5.25 disk?
    Is the hard disk a MFM disk and what is the controller? Why does it have to work on the first shot. Why not disconnect the hard drive and just boot from a working floppy first and then look at the hard disk? Who's Gotek software are you using?
    Dwight
    Dwight

    The 5.25" drive controller is a WD1793 and the drive was a standard 5.25" soft sectored floppy unit 512bytes/sector 40 tracks MFM

    The Hard drive has a home made SASI interface with a handfull of TTL chips as the disk itself does the hard stuff.

    The software I'm planning to use is the ICAS USB floppy manager 1.40. I already have a USB formated using the ICAS software

    I am very concerned about the state of the hard drive as it does make some strange noises at times. So I want to get everything off as fast as I can using the Gotek, get the Gotek to be bootable and then I can tinker as much as I like as I have a recovery route. I also want to limit any writes to the HD so no assembly, file creation unless absoluteley necessary. I suspect some things are missing already and that could be a result of invalid DBP's.


    Pete

  5. #5

    Default

    Quote Originally Posted by Eudimorphodon View Post
    If you're planning to use the Gotek with its out-of-the-box firmware I'd strongly recommend against it, it really is garbage. The free option for upgrading it is Flashfloppy:

    https://github.com/keirf/FlashFloppy

    You can also buy a special version of the HxC firmware for Gotek hardware:

    http://hxc2001.free.fr/floppy_drive_...rmwareForGotek

    Either of these is probably a much better option for working with a CP/M machine because they can directly support many standard emulator disk formats. The raw Gotek firmware is mostly hardwired to only support MS-DOS-like floppy formats and it doesn't do that particularly well.
    I am trying to keep this as simple as I can for now as I'm trying to re-learn something I've had nothing to do with for over 30 years. So, as I said to Dwight, recovery of files is #1 priority then I can look at tidy system builds.

    Pete

  6. #6

    Default

    I had another go at understanding the CP/M 2.2 Alteration Guide. I had a bit of an epiphany moment and created a spreadsheet to capture my thoughts. Here it is so you can review what Iíve done.

    https://drive.google.com/open?id=1Je...89OGqppISTZYQe

    The Floppy drive types are examples of Ďtypicalí IBM drives that have been in use over the years.

    The hard drive parameters are an attempt to reconcile my existing set and some of the numbers used seem a bit strange (4 sectors per track, really?). However, based on the input data the spreadsheet produces the same results as I have in my configuration, particularly for the computed values for the DPB. So, I must have known a bit about what I was doing back in the 80ís

    I need to go and investigate the hard drive and see where I got the basic disc parameters from. It came from an auction with no paperwork and Iíve not been able to find anything in recent searches.

    Please review the spreadsheet and tell me what Iíve got wrong (apart from the HD specs)

    Regards

    Pete

  7. #7

    Default

    Quote Originally Posted by Dwight Elvey View Post
    You are talking about a soft sectored 5.25 disk?
    Is the hard disk a MFM disk and what is the controller? Why does it have to work on the first shot. Why not disconnect the hard drive and just boot from a working floppy first and then look at the hard disk? Who's Gotek software are you using?
    Dwight
    Dwight

    I hadn't ignored your post and had replied yesterday but as a newby I have to wait for the moderator to approve my posts. It looks like that restriction has now been removed. Hoepfully it will be released today otherwise I'll do it again.

    Pete

  8. #8

    Default

    Quote Originally Posted by Eudimorphodon View Post
    If you're planning to use the Gotek with its out-of-the-box firmware I'd strongly recommend against it, it really is garbage. The free option for upgrading it is Flashfloppy:

    https://github.com/keirf/FlashFloppy

    You can also buy a special version of the HxC firmware for Gotek hardware:

    http://hxc2001.free.fr/floppy_drive_...rmwareForGotek

    Either of these is probably a much better option for working with a CP/M machine because they can directly support many standard emulator disk formats. The raw Gotek firmware is mostly hardwired to only support MS-DOS-like floppy formats and it doesn't do that particularly well.
    Hi

    I hadn't ignored your post and had replied yesterday but as a newby I have to wait for the moderator to approve my posts. It looks like that restriction has now been removed. Hoepfully it will be released today otherwise I'll do it again.

    Pete

  9. #9

    Default

    I've now cracked the mystery of why my hard disk was set up having tracks with only 4 x 128byte logical sectors and also why my config had offsets of 16,766,2056 and 8208 for the 4 hard disk 'partitions'. The hard disk doesn't have tracks it only has 20,480 5i2byte sectors making it a 10mb drive. My DPB is set up wth tracks referencing each physical sector.

    It may well be a result of the way I designed my TTL based SASI/SCSI1 controller doing track translation in BIOS. I'll re-read my copy of the "Western Digital Storage Management Handbook 1986" as that was my reference when I built the TTL controller.

    What I had done confused me now but back in the 80's it seems I had some idea what was doing

    Pete

  10. #10

    Default

    Quote Originally Posted by Doubletop View Post
    I've now cracked the mystery of why my hard disk was set up having tracks with only 4 x 128byte logical sectors and also why my config had offsets of 16,766,2056 and 8208 for the 4 hard disk 'partitions'. The hard disk doesn't have tracks it only has 20,480 5i2byte sectors making it a 10mb drive. My DPB is set up wth tracks referencing each physical sector.

    It may well be a result of the way I designed my TTL based SASI/SCSI1 controller doing track translation in BIOS. I'll re-read my copy of the "Western Digital Storage Management Handbook 1986" as that was my reference when I built the TTL controller.

    What I had done confused me now but back in the 80's it seems I had some idea what was doing

    Pete
    I've now updated my spreasheet to correct the definition for my Hard Disk. The new file is here


    https://drive.google.com/open?id=1FXw5JjusbklP0cY9gXNKJZK5mg4f7YMj


    I've added the values in my system DPB to compare them with the spreadsheet generated values. The differences are highlighted in orange. I think the only significant problem would be the EXM for HDA. I don't believe the track offsets being higher than the derived values would be a problem and the disk is nowhwere near full, maybe 100 files on each logical disk and nowhere near the 512 or 1024 catered for.

    Pete

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