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Thread: Drive parameters for Gotek USB disk

  1. #11

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    You are already beyond me. I am not familiar with ICES. I do know that HxC works with the Gotek and has built up a library of older disk formats. It sounds like you are more along than I can help, though. I assume you've made or already have the BIOS level code for your machine. Most CP/M machines expected 128 byte sectors but with deblocking code it works with larger sector sizes. That is about all I know.
    Dwight

  2. #12
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    Hello,

    I'm not sure what you could do within CP/M 2.2. As far as I know, the DPB etc needs to be - in effect - hard coded within the system, so maybe you need to accept that the Gotek can operate as one format only, unless you can work a way of switching.

    One of the books I have gives a fair bit of detail about the CP/M (2.2) file system, and the disk parameters etc, incl some tables for the options. This is: The Programmer's CP/M Handbook by Andy Johnson-Laird. This may be accessible via the web. Chapter 3 about the File System is most relevant.

    Depending on how far you want to go, I would refer you to the Amstrad implementation of CP/M 3, esp for the PCW computers (I have an 8256 still working happily). This system uses an extension to the DPB, referred to as the XDPB. Each disk (format) includes 16 bytes of data to update the XDPB (and thereby the DPB) to the correct parameters and this happens immed the disk is first read. This is of course very useful for people using the Gotek type of drive as it doesn't matter what the images are, as soon as the image is accessed then the data is read from the first sector with the XDPB data for that specific format and the system parameters are updated, and the rest of disk access can proceed accordingly. If you WANT to allow your Gotek to do something like this, maybe you could try to achieve something similar within 2.2?

    Geoff
    Vintage Devices: Epson HX-20/TF-20, Amstrad PCW 8256 (with extras), 386 and 486 PCs with 5.25 and 3.5 floppy drives, Pentium 75 with Roland LAPC-I midi card

  3. #13
    Join Date
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    Quote Originally Posted by Doubletop View Post
    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.
    So the reason I'd strongly recommend hacking one of the alternate firmwares onto your Gotek (with FlashFloppy you won't even need to do any soldering if you use the USB cable method) is unless the native firmware has improved *a lot* I'm pretty sure the only option you're really going to have is to set up your CP/M machine to essentially use a 100% DOS compatible sector/track/density layout. Last time I checked the Gotek firmware couldn't even detect what data rate the machine was trying to use; that's why they sell separate versions labeled as 720k, 1.2mb, and 1.44mb compatible. So if you bought the 1.44mb Gotek you're basically going to have to make your machine do 80 tracks, 18 sectors/track, 512 byte sectors at a 500khz data rate. I'm not sure it'll make sense of anything else. (And if that's not a problem then, sure, you're probably good.)

    The web page still shows them selling those different data rate models, so unless there's been a quiet revision I assume that's still true.

    The advantage of the alternate firmware choices is you can use file formats like .hfe for the emulated disks, which support basically arbitrary geometries and data rates. All the standard-interface goteks use the same SoC so the alternate firmwares will install on any of them.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  4. #14

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    Hi
    I'm still trying to make sense of what you are doing. On the first post you say that you got the Gotek that can do 720K 1.2m and 1.44M. It sounds like your setup used 360K disk and MFM or double density. The Gotek that are setup as 720K 1.2m or 1.44M will not do 360K. The Gotek is not a USB floppy drive, it is a floppy emulator using USB. It can only emulate one of 720K 1.2m or 1.44M formats at one time with the firmware on it. It doubt it will do 360K with the firmware on it. Don't confuse a physical 1.2M drive on a PC reading or writing 360K with what a floppy emulator does. These are not the same thing.
    Both Endimorphodon and I have been trying to steer you to what you need. You need firmware on the Gotek that will do 360K 512 sector.
    Dwight

  5. #15
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    The "720k" Gotek would *probably* work with a 360K format, since it would at least be the correct data rate but with fewer tracks, but I'm still pretty sure the format would have to *really close* to a standard DOS format in terms of sector length, address marks, etc. But, yeah, if you have the 1.44MB Gotek it's right out unless they've make them more flexible.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  6. #16

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    Guys

    Thanks for your input, some of it may not be entirely on track with my plans but the fact you’ve taken the time to write and I read what you have written makes me take stock and provides the triggers for my thinking. In my first post I was in a bit of a spin and couldn’t get my head around the alteration guide or what I’d done in the past. I am now getting into it.

    Lets take stock….

    My system is a homebrew, built around 1982 with 8” drives, then 5.25” and by 1989 a 10Mb hard disk. It is CP/M 2.2, I had considered going to one of the later versions and have some of the parts but never got around to it. PC’s took over my interests.



    This is it, not pretty but it work(s/ed). Eurocard back plane video and ram from ETI PCB’s much modified, and the rest hand wired.

    The disk controllers are all home made.

    8” and 5.25”



    Hard Drive SASI/SCSI1 (on left) with just a handful of TTL



    The hard drive works and is making strange noises so I need to back it up ASAP. I’ve managed to PIP the source and .HEX for the BIOS, BDOS, Boot and a few utilities so I have them on a PC but moving .COM files won’t work as all I did at the PC end was screen scrape the listings.

    The 8” and 5.25” drives are long gone so I’m going to use the Gotek. I don’t need any special format for the floppy drives so any standard IBM format will do, its just needs the correct parameters in the DPB. That was really my original question as I was stuck, and you guys have ‘unstuck’ me I think.

    I don’t have a Gotek yet so I can’t confirm this. I was wondering why they came in so many different types and I now believe that to be because the in-built firmware formats to one format for specific target machines. However, searching for information about the devices I came across this on Youtube.



    He uses the ICAS software to pre-format the USB on a PC and you can select 1.4M, 1.2M or 720K. Only using 100 files I can get 140Mb of storage and my hard drive is only 10Mb so plenty to start with. I couldn’t find the software on the ICAS site but the guy who posted the video has it here

    https://www.philscomputerlab.com/got...-emulator.html

    As I said any format will do me as long as I can set up the DPB parameters, hence this thread. I guess that upgrading the Gotek firmware has been suggested as some people need to do that to get the drive working with their proprietary system. It’s different for me as I can modify the system to suit the drive. The spreadsheet I've posted just needs the drive parameters entering and some design deiscions made like block size, directory entries and reserved tracks and the DPB parameters are generated. The only one that affects system sizing in the Allocation Vector (ALL0x) sizing. If it is larger than the existing size, say when going from 360kb to 720kb the BDOS will likely overwrite anything beyond the original definition. Fortunatley, I have that space available as I can use the space reserved for a second floppy.

    Once I get it going, I can then get everything off the hard drive and after that look at any firmware upgrades to the Gotek. At $25 I may well buy another one for messing with. However, I’m still waiting for the drive to arrive once it does and I get an opportunity to check things out and test the theory. I’ll update this thread as I go and no doubt have more questions

    Once again thanks for your help so far

    Pete
    Last edited by Doubletop; January 10th, 2020 at 01:37 PM.

  7. #17

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    cool build!

    you should really get another 8" drive going for this baby

  8. #18
    Join Date
    May 2011
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    Quote Originally Posted by Doubletop View Post
    He uses the ICAS software to pre-format the USB on a PC and you can select 1.4M, 1.2M or 720K.
    The way the default Gotek firmware works is it relies on having the USB stick "partitioned" into a bunch of RAW floppy-sized slots. The ICAS software lets you select the different sizes so you can set up your USB stick to work with the particular type of Gotek you bought, IE, the 1.4, 1.2, or 720k. (And subsequently when the software runs it'll partition the flash drive into a hundred or whatever identical size slots.) That does *not* mean the Gotek drive itself will recognize and work with a flash drive or host system that uses a different geometry.

    I get that you're free to set your own disk geometry from your host system, and that's great. The point that was being made by suggesting an alternate firmware is with the stock one you *will* have to conform very closely to the parameters of the firmware of the particular Gotek you bought, which *expects* that you'll be reading and writing this geometry:

    MFM encoding
    500kbit/s data rate
    300 RPM "spindle speed"
    80 tracks
    2 sides
    18 sectors per track
    512 byte sectors

    If that's not a problem for your hardware than the off-the-shelf firmware might work. The one point that comes to mind: does your 5.25" drive controller support the 500kbs data rate? If it doesn't you'll have to hang the drive off the 8" drive controller. Unless Goteks have suddenly grown density detection, which, again, seems unlikely given they are still selling 720k units as separate skews.

    Again, whatever works for you. If you want to try to make it work before the Gotek shows up if you have a real 3.5" high density floppy drive lying around that's your target.

    (Another significant advantage of the alternate firmwares, on top of how they're adaptive enough that they may well work out of the box with whatever geometry you were using on your physical floppy disks, is they *don't* require a proprietary format on the Flash drive or strange tools to extract the data on and off said drive; you use a standard fat/fat32 format and just drop standard floppy images onto it. Said images can then be manipulated with common emulator/data transfer tools.)
    Last edited by Eudimorphodon; January 10th, 2020 at 02:38 PM.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  9. #19

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    Quote Originally Posted by Eudimorphodon View Post
    The way the default Gotek firmware works is it relies on having the USB stick "partitioned" into a bunch of RAW floppy-sized slots. The ICAS software lets you select the different sizes so you can set up your USB stick to work with the particular type of Gotek you bought, IE, the 1.4, 1.2, or 720k. (And subsequently when the software runs it'll partition the flash drive into a hundred or whatever identical size slots.) That does *not* mean the Gotek drive itself will recognize and work with a flash drive or host system that uses a different geometry.

    I get that you're free to set your own disk geometry from your host system, and that's great. The point that was being made by suggesting an alternate firmware is with the stock one you *will* have to conform very closely to the parameters of the firmware of the particular Gotek you bought, which *expects* that you'll be reading and writing this geometry:

    MFM encoding
    500kbit/s data rate
    300 RPM "spindle speed"
    80 tracks
    2 sides
    18 sectors per track
    512 byte sectors

    If that's not a problem for your hardware than the off-the-shelf firmware might work. The one point that comes to mind: does your 5.25" drive controller support the 500kbs data rate? If it doesn't you'll have to hang the drive off the 8" drive controller. Unless Goteks have suddenly grown density detection, which, again, seems unlikely given they are still selling 720k units as separate skews.

    Again, whatever works for you. If you want to try to make it work before the Gotek shows up if you have a real 3.5" high density floppy drive lying around that's your target.

    (Another significant advantage of the alternate firmwares, on top of how they're adaptive enough that they may well work out of the box with whatever geometry you were using on your physical floppy disks, is they *don't* require a proprietary format on the Flash drive or strange tools to extract the data on and off said drive; you use a standard fat/fat32 format and just drop standard floppy images onto it. Said images can then be manipulated with common emulator/data transfer tools.)

    Thanks, that’s just the sort of information I was looking for. The disk controllers is a WD 1793 and they can do IBM 3740 format both single and double density and one of my configs is for double sided. Spindle speed and data rates for the original drives would have been 300Rpm and 500Kbit/s.

    In the interest of not introducing too many variables at the start I am got to try the out of the box Gotek just to get the data off the hard drive even if it is untidy. After that I’m happy to try alternative firmware.

    Pete

  10. #20

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    Quote Originally Posted by maxtherabbit View Post
    cool build!

    you should really get another 8" drive going for this baby
    An interesting dea but I'm not sure I'd be able to find one or the media.

    Pet

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