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Thread: CP/M question...

  1. #41

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    Quote Originally Posted by ziloo View Post
    Was it really a whole new concept each time or a bug fix?


    ziloo
    It was more the blindness to see what was possible and how soon it might happen.
    Moore's law could be applied to a lot of things.
    Dwight

  2. #42
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    Default Converting Directories from cp/m 2.2 to cp/m 3.0

    In the following statement:

    "With the introduction of password protection and date/time stamping of files in CP/M 3,
    changes had to be made to the CP/M 2.2 format disc directories. To retain compatibility,
    a separate program (INITDIR.COM by Amstrad for Amstrad?) was supplied which re-formats
    the directory of a CP/M 2.2 format disc so that every fourth directory entry holds
    the passwords and date/time stamps of the previous three entries."

    Did this method become popular, or it was a fab...


    ziloo
    Last edited by ziloo; Today at 06:36 AM.

  3. Default

    INITDIR is standard CP/M3.

  4. #44
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    Default

    CP/M 2.2 has been the most popular, with 3 occupying a very small part of the market. While the file dating and password (wasn't that borrowed from MP/M?) is nice to have, few applications made use of the feature--and the number of available directory entries was reduced by 25%.

  5. #45
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    Default

    Amstrad was a major user of CP/M 3 and enhanced versions of CP/M-86 with the date functions so if ziloo is in a region where encountering them is common, ziloo will have to keep it in mind.

    Then there is always the fun chance of encountering one of the alternate third party add-on date systems for CP/M 2.2. Nothing like encountering a directory shows up as corrupt because I don't have the software that made the disk.

  6. #46
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    Default

    But if you're writing "portable" applications, stick with 2.2 as your Bible--and it's not a bad idea to stay away from Z80-specific instructions. There were plenty of 8080/85 CP/M systems out there.

  7. Default

    CP/M 3 and MP/M-II share a great deal of code, and also share much/all of the directory/file extensions. The BDOS source code has if-defs for MP/M, although I don't know if that was how the MP/M-II BDOS was actually created. Most of the MP/M-specific features were added through the XDOS component.

  8. #48
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    I ported MP/M 1.0 before CP/M 3 (or CP/M plus) was available. When I saw the CP/M 3.0 literature, the similarity immediately struck me.

    My experience with MP/M 1.0 was very mixed--stability was a real issue. MP/M 2.0 was much better, but mostly useful only if you had applications that were designed for it. I still have my MP/M 2.0 OEM kit, including DRI's sales literature for the soon-to-be CP/M-86.

    My feeling was that CP/M 3 came out of MP/M because of the very small market for the latter. Getting a BIOS (BIOS+XIOS) going can be a bit challenging, particularly if you don't have the regular method of bankswitching (16KB banks). Since our system was entirely interrupt-driven (even to the screen refresh), MP/M was a pretty good fit.

  9. Default

    A lot of the DRI advances came at a point when DOS was taking over - regardless of what was the better technology. Another example was choosing 8086 over 68K (or NS 16016/32032, or...). DRI was working on graphical support, multi-tasking, multi-user, networking, etc. But all of this got passed over because it wasn't DOS. One major use for MP/M was for CP/NET servers. So, in a multi-tasking environment as opposed to multi-user. Lesson is, it's not who gets there first or has the best technology, it's who your friends are... We all know the stories of why IBM went with MS-DOS instead of CP/M... but I'm not convinced all of it is true, based on my interactions with DRI.

  10. #50
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    CP/M, at least until the time of DOS cloning could not seem to wean itself from the single flat-mode directory structure. I believe that this was their downfall. Once you admit hard disks and multiple users, the problems with the original scheme become obvious. Around 1979, we were looking at hard drives and Shugart sampled us the SA4000--but in its 40MB form, which is more storage at the time than CP/M 2.2 could handle. If this represented just the start, we were going to have serious problems. I recall writing a draft of a proposed disk label at the time, wondering if 32-bit sector numbers would be adequate in a few years.

    Atari ST GEM for example, was provided on a DOS-like OS, even though CP/M-68K was proposed originally.

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