[HN Gopher] Apple II Emulation Evaluation (2022)
       ___________________________________________________________________
        
       Apple II Emulation Evaluation (2022)
        
       Author : mmphosis
       Score  : 24 points
       Date   : 2024-01-02 20:46 UTC (2 hours ago)
        
 (HTM) web link (juiced.gs)
 (TXT) w3m dump (juiced.gs)
        
       | zellyn wrote:
       | If you're interested in Apple II emulators, the #emulators
       | channel on the Apple2Infinitum Slack is a great place to ask
       | questions or chat. Invites available here: http://apple2.gs:3000/
        
       | retrac wrote:
       | The Apple II is rather hard to emulate correctly. While most
       | Apple II software is relatively easily supported, some corner
       | cases are absolutely brutal to get right.
       | 
       | For example, you can mostly treat the video system as a dumb
       | framebuffer. But there are cases where this fails. It is possible
       | to detect the vertical blanking period on an Apple II. [1] This
       | relies on capacitance on the Apple II bus and very strict timing.
       | On a real Apple II the value read from a non-existent memory
       | address is not always 0, sometimes it's the last value read,
       | which is sometimes the last value read by the video system which
       | is overlapped with the CPU. To emulate this right, you need to
       | emulate the whole video system lock-step and cycle accurate with
       | the CPU.
       | 
       | The disk system is another major pain point. All of the timing
       | and track movement is handled in software. Arbitrary disk formats
       | can be created in software. One single spiral track was used by
       | some games as copy protection. To support the Disk II completely
       | requires emulating at a much lower level than that of 256 byte
       | sectors. Some emulators going all the way for accuracy, use a
       | structure, that is basically a map of the flux transitions on
       | disk.
       | 
       | [1] http://deater.net/weave/vmwprod/megademo/vapor_lock.html
        
       ___________________________________________________________________
       (page generated 2024-01-02 23:00 UTC)