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Thread: What 8088 instructions work on segment registers?

  1. #21
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    From my own experience, I recall the 68008 as being a real slug in terms of performance.

    The 68K being utterly impractical evidently didn't stop Apple, did it? Or Atari, or Commodore...

    The CS9000 showed that IBM was well aware of the 68K and that a system using it would be significantly advanced.

    I remember getting the technical information on the 68K at either a Wescon or NCC (shows back then are a blur) and asking about the possibility of using the "invalid memory address" trap to implement virtual memory. The guy at the Motorola table sighed like he'd heard the question a thousand times that day and said no--not all of the trapped instructions were restartable, so no virtual memory. Of course, if you avoid certain instructions, such as MOVEM, then you can, in fact, do it--which Apple learned.
    Last edited by Chuck(G); May 16th, 2017 at 01:41 PM.

  2. #22

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    I'm not really familiar with the behind-the-scenes story on the IBM PC, but it really seems like they had no concrete goal for it other than "get something into the personal computer market with our name on it," once they realized they couldn't just ignore the field altogether.
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    "'Legacy code' often differs from its suggested alternative by actually working and scaling." - Bjarne Stroustrup

  3. #23

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    In 1981, even 8086 seemed too expensive for the PC, and 68000 would have made it even more expensive.
    It was 1984/85 when Apple, Atari and Commodore introduced their 68K stuff.

  4. #24
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    Sure--so why was IBM in such a hurry if they clearly knew about technology on the offing? They could have gotten the jump on Apple.

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    Quote Originally Posted by Chuck(G) View Post
    Sure--so why was IBM in such a hurry if they clearly knew about technology on the offing? They could have gotten the jump on Apple.
    IBM wanted a PC design in a year. Waiting another few years could have allowed one of the microcomputer companies to have been established as a dominant player in the market the way DEC had managed. Thus, IBM wound up making an 8088 modification of the Datamaster with bonus cassette port.

    Though it might have been hilarious to see what type of closed proprietary box the IBM post-consent decree would have resulted in considering the historical examples of the PS/2 and Topview.
    Last edited by krebizfan; May 16th, 2017 at 03:57 PM.

  6. #26

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    BTW, note that IBM PC was supposed to compete against 6502 and Z80 machines, nothing more.
    Here, 8088 was clearly better.

  7. #27
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    So, basically lack of vision. White shirt and dark tie. In a lot of ways, even the Apple II was a better system.

  8. #28

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    Excepting the guys on the actual skunkworks team, "Lack of Vision" could pretty much have been IBM's official slogan for the 1980s.
    Computers: Amiga 1200, DEC VAXStation 4000/60, DEC MicroPDP-11/73
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    "'Legacy code' often differs from its suggested alternative by actually working and scaling." - Bjarne Stroustrup

  9. #29

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    I'm not sure about the "lack of vision", it's likely they had a vision, just different from the vision of PC users.
    IBM's primary market has always been mainframes and other big iron.
    First, they were reluctant to enter the "micro" market at all, later they were reluctant to add certain features to PC, it seemed they did their best to make PCs unable to compete with their bigger machines:
    * 5150 was supposed to be just yet another CP/M box, only marginally better than competition
    * 5170 was intentionally slowed down with unnecessary memory wait states
    * IBM turned down Microsoft's multitasking DOS
    * IBM was late with 80386
    * even when they finally introduced 386 machines, their brand-new OS/2 was still 16-bit

    In the 80s, if you went to IBM and asked for a machine to easily process data structures >64KB, they wanted to sell you an S/370, or something like that.

    And from a perspective, that strategy has been quite a success. IBM is still alive, countless PC-centric vendors, notably Compaq, are dead.
    Last edited by Xacalite; May 17th, 2017 at 02:17 AM.

  10. #30
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    Well, there's the blue sky value of IBM and the concentration on business and government applications.

    I recall that a couple of friends of mine who were running a small business, sat down with the sales people at Computerland. Hard number crunching, they determined that the 5150 was too expensive for the limited value and went with Bill Morrow's package deal for about $1000 less. They were very happy with the decision.

    I suspect that IBM would have given up on the PC had it not been for the advance of cheaper clones. Had that not have happened, I think that the PC would have been written off. Even back then, I looked at the NEC APC and considered it to be the much better deal.

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