Re: A89: TI89 ROM vs HP49 ROM -- No More TI Bashing!!!

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Re: A89: TI89 ROM vs HP49 ROM -- No More TI Bashing!!!


If it has, they don't use it :)
I havn't checked all this personally, but my friend Johan Borg (who lives about
500m away) has done some serius digging and checked chipselect and stuff like
that, and he is _good_ so I belive what he says.
And btw, they have no reason to have a rom in the custom chip because of the
feutures in the flash chip that makes it possible to permanently write protect
certain blocks. (the .pdf with the specs of the flash in the 89 is at my
homepage, http://alh.dhs.org/ti89/
so in short, some block(s) are permanently write protected, containes bootloader
and stuff
and a large number of blocks are write protected, but it is possible to
temporarily "release" the write protection (system routines for user flash-area,
and the "bug" for the rest)

the reason why it is possible to totally destroy the calc is that the bootloader
checks a byte in the area that is possible to write to via "the Bug", and if
this byte is wrong, it refuses to do anything.

//Olle

Adam Davis wrote:
> 
> So what you are saying is that you're *certian* that the custom 68k chip
> motorola makes just for TI has no ROM in it?
> -Adam
> 
> Olle Hedman wrote:
> >
> > `there is no "real rom" in the ti89. only flash. but there is a part of this
> > flash that is fully write protected and impossible to disable the
> > writeprotection on. bootloader and stuff lives there..
> > That is equvialent to "real rom"...
> >
> > //Olle
> >
> > SirKnight wrote:
> > >
> > > >If ROM can be edited so can serial numbers (right?).  I'll stop talking
> > > >illegal for now though.
> > >
> > > Not if it's hardware.  I've see little 3 wire chips a company made that
> > > contained a serial number.  I doubt that TI would put the serial number in
> > > the flash.  But it sorta makes sense.  If the code to write to it is
> > > actually in a real ROM (not flash) then it could be done easily at the
> > > factory when writing the code to the calcs.
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