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  • MP/M 815, CCDOS of its variations and HDD formats ?

    From Gary S@21:1/5 to All on Sun Mar 13 21:41:51 2022
    My memory is failing me a bit as I never really got too involved in the later stages of the various DR operating systems after they were sold on.
    So my question is how backward compatible where they ?
    I am thinking what were the issues of a cp/m80 programs accessing the hard/floppy disk, the various formats, layouts etc.

    Gary
    vk2zbb

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  • From Peter Higgins@21:1/5 to [email protected] on Tue Mar 15 13:51:19 2022
    On Sunday, March 13, 2022 at 9:41:53 PM UTC-7, [email protected] wrote:
    My memory is failing me a bit as I never really got too involved in the later stages of the various DR operating systems after they were sold on.
    So my question is how backward compatible where they ?
    I am thinking what were the issues of a cp/m80 programs accessing the hard/floppy disk, the various formats, layouts etc.

    Gary
    vk2zbb

    Presumably you are referring to the "8-16" versions of Digital Research CP/M, MP/M, and Concurrent CP/M or Concurrent DOS. These "8-16" versions were not developed directly by DR - they were customized versions developed by a couple of computer
    manufacturers for use on their own hardware systems, most notably CompuPro. All CP/M-80 BIOS calls were managed by the customized 8-16 operating system (including those accessing the floppy and hard drives) therefore either CPM/80 or CPM/86 applications
    could both be handled seamlessly. The method of implementation changed as the operating systems evolved, using the BIOS and a customized CCP in early versions, and a shell environment created by a "SWITCH" application in later versions. Backwards
    compatibility was excellent, provided the CP/M-80 application did not attempt to directly access hardware.

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  • From Douglas Miller@21:1/5 to All on Tue Mar 15 15:14:16 2022
    The hard disk formats you seem to refer to are filesystem, not track/sector, formats. Programs that made BDOS calls to access files did not need any special compatibility layer, unless they hard-coded redundant checks for the limits (e.g. instead of just
    letting the BDOS tell you when you exceed the file size limit they pre-emptively checked for that limit).

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  • From Gary S@21:1/5 to [email protected] on Tue Mar 15 14:54:19 2022
    On Wednesday, 16 March 2022 at 07:51:20 UTC+11, [email protected] wrote:
    On Sunday, March 13, 2022 at 9:41:53 PM UTC-7, [email protected] wrote:
    My memory is failing me a bit as I never really got too involved in the later stages of the various DR operating systems after they were sold on.
    So my question is how backward compatible where they ?
    I am thinking what were the issues of a cp/m80 programs accessing the hard/floppy disk, the various formats, layouts etc.

    Gary
    vk2zbb
    Presumably you are referring to the "8-16" versions of Digital Research CP/M, MP/M, and Concurrent CP/M or Concurrent DOS. These "8-16" versions were not developed directly by DR - they were customized versions developed by a couple of computer
    manufacturers for use on their own hardware systems, most notably CompuPro. All CP/M-80 BIOS calls were managed by the customized 8-16 operating system (including those accessing the floppy and hard drives) therefore either CPM/80 or CPM/86 applications
    could both be handled seamlessly. The method of implementation changed as the operating systems evolved, using the BIOS and a customized CCP in early versions, and a shell environment created by a "SWITCH" application in later versions. Backwards
    compatibility was excellent, provided the CP/M-80 application did not attempt to directly access hardware.

    Thanks Peter,
    Answered the basic for me, I just wondered how they managed the compatibility of hard disk formats etc between the different for os's.

    such as max 8mb for cpm80 compared to msdos limits.

    Presumably in the "switch" application it seems...

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  • From Douglas Miller@21:1/5 to Douglas Miller on Tue Mar 15 16:08:19 2022
    On Tuesday, March 15, 2022 at 5:14:17 PM UTC-5, Douglas Miller wrote:
    The hard disk formats you seem to refer to are filesystem, not track/sector, formats. Programs that made BDOS calls to access files did not need any special compatibility layer, unless they hard-coded redundant checks for the limits (e.g. instead of
    just letting the BDOS tell you when you exceed the file size limit they pre-emptively checked for that limit).

    Well, except for possible differences between 16-bit and 8-bit FCBs, and the like.

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  • From Peter Higgins@21:1/5 to All on Tue Mar 15 17:24:35 2022
    Most of CompuPro's 8-16 systems used the CPM/86 and Concurrent CP/M86 file systems on both floppy disks and hard drives.
    Only the final versions of CompuPro's Concurrent CP/M86 and Concurrent DOS used the MSDOS FAT file system.
    The "SWITCH" application provided with the later 8-16 operating systems just needed to set up a virtual CP/M-80 environment, translating BDOS calls between it and the 8-16 operating system.

    Answered the basic for me, I just wondered how they managed the compatibility of hard disk formats etc between the different for os's.
    such as max 8mb for cpm80 compared to msdos limits.
    Presumably in the "switch" application it seems...

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