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Re: How does a Spectrum emulator work?

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Yes but this only really worked because the z80 in the 81 machine was mostly 
taking time building the picture you saw. That was why it had fast and slow 
mode.
 As a matter of interest, did anyone manage to emulate the tape loader from 
the 81. it was flaky at the best of times on the original machine.
 Brian

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<jbkoelman.sp@gmail.com> wrote in message 
news:a8eaf40e-89f6-41d6-916a-c68a358acf79@googlegroups.com...
> In the documentation of the Z80-emulator there was some explanation of the 
> emulator.
> Exact as described for each opcode a small routine was coded.
> On a PC enough memory is available and the Z80-emulator needed 64K for the 
> emulation since each opcode was emulated at address #nn00 where nn held 
> the number of the opcode. Each opcode had therefore 256 bytes room for the 
> routine.
>
> Also the minimal requirements of the host computer were mentioned. For 
> speed you needed at least 10x faster than emulated computer.
> More memory (original and emulation must be loaded) and finally same or 
> higher screenresolution to display the screen.
>
> These rules apply quite well, although it didn't stop me from trying to 
> code a ZX81 emulator for the ZX Spectrum and the Sam Coupe which both only 
> have a bit faster CPU than the ZX81 and therefore do not comply to the 
> speed rule.
>
> On the SAM coupe we were able to not truly emulate original code, but just 
> let it run and only built a screen during intrupt.
> This made a full speed ZX81 possible.
>
> For the ZX Spectrum there is a full emulator, but the emulator runs 
> certain parts of the ROM in a ZX-Spectrum mode, using the moved addresses.
> With this trick a lot of games run well on the ZX Spectrum too. 

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Thread

How does a Spectrum emulator work? bit-naughty@hotmail.com - 2016-04-02 09:40 -0700
  Re: How does a Spectrum emulator work? Guesser <alistair@zxnet.co.uk> - 2016-04-02 18:14 +0100
    Re: How does a Spectrum emulator work? jbkoelman.sp@gmail.com - 2016-04-02 12:43 -0700
      Re: How does a Spectrum emulator work? "Brian Gaff" <briang1@blueyonder.co.uk> - 2016-04-02 21:22 +0100
        Re: How does a Spectrum emulator work? jbkoelman.sp@gmail.com - 2016-04-02 13:49 -0700
        Re: How does a Spectrum emulator work? Leiradella <aleiradella@gmail.com> - 2016-04-02 14:01 -0700
  Re: How does a Spectrum emulator work? "Brian Gaff" <briang1@blueyonder.co.uk> - 2016-04-02 21:17 +0100
  Re: How does a Spectrum emulator work? Leiradella <aleiradella@gmail.com> - 2016-04-02 13:56 -0700
  Re: How does a Spectrum emulator work? Andre Majorel <cheney@halliburton.com> - 2016-04-06 11:56 +0000
    Re: How does a Spectrum emulator work? Tyrell <on4ssc@gmail.com> - 2017-01-28 15:59 +0100
      Re: How does a Spectrum emulator work? AndyW <Andy@nojunqmail.com> - 2017-01-30 07:33 +0000

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