[A89] Re: Emulators


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[A89] Re: Emulators




> > I would probably have to say the emulator from TI would be more
> > accurate than vti.

I've been using the simulator since the Alpha v0.01 revision and VTI since
it first came out, so let me expand upon Zeljko's comments:

> Wrong. VTI is much more accurate than TI-SDK emulator...
> Try to run any grayscale program on TI-SDK emulator, for fun...

I agree that TI's simulator doesn't even attempt to provide full, perfect
emulation.  The simulator was only intended for app development, and thus is
only intended to accurately emulate a few aspects of the calculator.  It
always believes itself to be a HW2 AMS 2.05 calculator, although considering
the portions of the calculator that are emulated accurately, the HW version
is not really an issue.

VTI, on the other hand, provides very accurate emulation of HW1 calcs.  Its
HW2 emulation, however, is certainly good enough to use for emulating most
programs, but has known problems.  Quick example: VTI doesn't automatically
set the HW2 contrast correctly.  This is one minor side effect of a much
larger issue, which is that some HW2 ports return different values than
their HW1 equivalents, and we don't know why.  Switching the location of the
LCD data is totally blocked out in HW2 emulation, but I still believe that
the calc itself may be capable of using that trick with certain addresses.

Note that VTI has no true app support whatsoever.

> > I would think this would be true since TI would probably want
> > everything to run exactly as it would on the real deal
>
> No. TI wants to emulate exactly just these features which they want
> to support on their calculators...

Exactly.  TI does not seek 100% accurate emulation; they merely seek to
create a tool that performs suffienciently for application development.  The
true key features of the simulator are twofold: first of all, app support,
and second, the integrated debugger, stepping through code, and the watch
window.  This makes it very useful in developing standard applications using
the SDK-documented portion of the interface.

If anyone else out there uses the simulator, I'll warn you now that you MUST
upgrade to Flash Studio Beta 3 ASAP.  Many problems with past betas allowing
programs to run that shouldn't (particularly ones that use complex
calculations in real mode) have been fixed.  It's been making great strides,
although once again only in the areas in which it is intended to be used.

> > but with vti the hardware might not all be correctly emulated plus
> > there's a chance for errors when it runs the rom. There's an easy
> > way to find out which one is more accurate...run it on a real calc
> > and see which one it runs like.
>
> VTI is very far from perfect, but TI-SDK emulator is really shitty
> in comparing with VTI, from the hardware exactness point of view...

VTI's emulation of almost all asm programs on a HW1 calculator is extremely
accurate.  There are a few features of the real hardware that lack support
(Olle's changing of the virtual LCD width comes to mind), but most programs
will never got near any of these.

Once again, the quality of VTI's HW2 emulation is not fully known, but I
don't think it's very subsantial unless you change the location that the
memory-mapped LCD reads from.

The SDK is intended for app programming only, and has a very useful/poweful
integrated debugger.  Use the SDK if you're writing apps that are restricted
to TI-documented functions, or VTI otherwise.  The best test is still that
of a real HW2 calc =)

    -Scott




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