[HN Gopher] The Architecture of the Lisa Personal Computer [pdf]
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       The Architecture of the Lisa Personal Computer [pdf]
        
       Author : ingve
       Score  : 19 points
       Date   : 2022-12-27 18:59 UTC (4 hours ago)
        
 (HTM) web link (bitsavers.org)
 (TXT) w3m dump (bitsavers.org)
        
       | KerrAvon wrote:
       | The perception of Unix at that time is very interesting -- this
       | was way before X existed (X would also not have been suitable by
       | this definition when it did become available, of course). The
       | NeXT UFS variant in 1997 was also probably still unreliable by
       | this definition.
       | 
       | > However UNIX is a relatively large operating system with
       | several features such as a multiuser timesharing capability, user
       | accounting, and protection which would be wasted in a personal
       | computer such as the Lisa. Since the Lisa would be used by people
       | who were not computer experts, the system must be very robust.
       | However, the UNIX file system is fragile and unreliable [10),
       | [14]. If the power is interrupted or a system crash occurs the
       | UNIX file system can easily be damaged. Unless a systems
       | programmer is present to repair the damage, a user can easily
       | lose all his data. In addition, UNIX does not provide the general
       | inter-task communication facility that the Lisa requires. UNIX
       | memory management does not offer sophisticated sharing of code
       | and data between tasks. Finally, UNIX and alI other operating
       | systems do not provide the support for graphics, multiple
       | windows, the mouse, integration, etc., which are essential to the
       | Lisa. Such capabilities cannot be built on top of an operating
       | system but must be built in to work correctly and efficiently. An
       | attempt to modify UNIX to overcome all of these deficiencies
       | would have taken longer than designing a new operating system
       | with all of the needed capabilities.
        
       | Animats wrote:
       | If only the Motorola 68000 line hadn't taken so long to come up
       | with a usable MMU. Computing history could have been very
       | different.
       | 
       | 1979, M68000, CPU, instruction backout broken, so if you wanted
       | to handle page faults, you needed to avoid all multi-step
       | instructions.
       | 
       | 1993, M68010 CPU, fixed backout bug.
       | 
       | 1987, N68030 CPU with MMU, page faults work.
       | 
       | Early machines required boards full of extra hardware to work
       | around this problem. Which is why the Macintosh, unlike the Lisa,
       | had a plain 68000 MMU and a DOS-like OS hidden by a very nice
       | GUI.
        
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       (page generated 2022-12-27 23:01 UTC)