Re: LZ: Mach-85 (REAL TI Emulator!!)

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Re: LZ: Mach-85 (REAL TI Emulator!!)

On Sun, 12 Aug 1990, Chris Kline wrote:


> If your satisfied with TIEMU.zip or whatever the actual name of it is
> by Rob Taylor you must be insane.  Sure it's identical to the TI in
> every way, because it IS basically the TI cause it's a ROM dump which
> according to Texas Instruments is illegal to destribute.  It's also
> VERY limited and SLOW and can't even save to the hard drive.


OK, let me clear this up. TIEMU.ZIP contains NO ROM DUMP. It is COMPLETELY
LEGAL TO DISTRIBUTE IN THAT FORM. The end user supplies his own ROM dump
from his own TI-85. This is completely legal, as the owner of a TI-85 is
licensed to use the ROM from his calculator. What is illegal is the
distribution of TIEMU.ZIP with a ROM dump included. This is why at
ticalc.org we supply TIEMU.ZIP (without a ROM file), and the necessary
programs to dump your own ROM.


> It can be done, the only dilema is that Mach-85 doesn't throw everything
> in a ROM dump so you can't take the ZShell backup and install it. 


Perhaps there is some misunderstanding as to how TIEMU works. Basically,
the ROM dump TIEMU uses is a copy of the ROM in the TI-85. Neither the
TI-85, nor the TIEMU write to the ROM in the course of operation. Remember
ROM = Read Only Memory, and as such, it cannot, by definition be written
to. TIEMU does not "throw everything in a ROM dump." Indeed, it only reads
from the ROM file, and executes the instructions contained therein. The
reason TIEMU functions nearly identically to a TI-85 is that the emulator
creates a virtual machine, taking Z80 instructions, and translating them
to x86 instructions for execution, then returning the results in a
completely transparent (to the virtual machine) process.


Think of this system in terms of layes. A TI-85, superficially speaking,
has three layers:


Software (contents of RAM)
--------------------------
Firmware (contents of ROM)
--------------------------
Hardware (CPU, Screen, etc)


TIEMU emulates the hardware layer of the TI-85, like so:


  Software (contents of RAM)
------------------------------
  Firmware (contents of ROM)
------------------------------
 Hardware (emulated by TIEMU)
------------------------------
Real hardware (of host system)


I hope this clears up any misundestanding.


-Isaac


<pre>
--
Isaac Salpeter
the ticalc.org project
isaac@ticalc.org
<pre>
--
</pre>
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