[TI-H] Re: 89 hw versions


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[TI-H] Re: 89 hw versions




At 01:23 2001-04-11, you wrote:
>I don't think so, I believe just that the clock is sped up from the HW
>1....and the processors are tested to work at this frequency instead
>(12Mhz).

Depends on how you define difference. The chip is totally different.
I have images of both hardware versions on my site, 
http://alh.dhs.org/ti89/ so you can see the differences yourself.
The hw2 has a standard surfacemounted 68000 (SEC version), running at 
12MHz, while the hw1 has a custom chip, not only holding the processor but 
also a lot of port and chip select logic and stuff like that.
Those functions are in a seperate chip on hw2.
There is also differences in protection features. In hw2 they added a lot 
of stuff to make it hard for hackers to hack apps and such, one of the most 
annoying is that you can only execute instructions from a certain area of 
ram at one time.
It divides the memory in 4K blocks with a register telling what blocks you 
are currently allowed to execute from. This register can only be changed 
from routines located in rom, so TI has quite good controll of this.
This is one reason for the 24K limit in hw2 calcs.
There are ways to go around this, but that is out of the scoop of this 
mail, and I don't know the routines well enough anyway, since I have never 
tried it myself.

///Olle





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