A89: Hardware differences:
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A89: Hardware differences:
Ok, I'll sum up everything I've heard, and then speculate, and I'd like
those who know better to correct me where I make mistakes...
To my knowledge the major differences in the hardware between Version 1
and 2 of the TI-89 are:
-Faster speed (12 MHz vs 10 MHz)
-Different programmable logic (either different program and/or
different chip to keep people from messing with the ROM and
certificates)
-Different way of running the LCD
It's the last point I want to target. I've heard on this list that:
-You have to copy the display to itself in order to get the
display data to display
-Gray scale doesn't work, not because of lack of interrupts, but
because this copying to self takes too much time
I'm speculating that TI put the display refresh functions onto another
chip. This would do a few things, firstly either this new chip has to
share memory with the 68k processor, OR it has it's own memory. I'm
banking on the latter. Chances are also good that it has enough memory
to have pages. This sort of memory would require an extra copy
operation. I can't think of another reason as to why it would need to
be copied to itself before it could display.
What makes me think this are the reasons above, but are also the reports
of a significantly faster ti-89. People who have used both versions of
hardware with AMS 2 point out that HW 2 is still noticeably faster. So
that rules out the idea that the speed increase is only caused by the
better AMS 2. Furthermore, a 2 MHz difference in clock speed may not
account for the speed increase. It is, however, still a 20% increase,
so it may be the reason, in which case this whole argument is invalid.
However, the 68k processor in the ti-89 HW1 and ti-92/+ spends a great
deal of time refreshing the LCD display, which is one reason the ti-89
seemed faster than the ti-92, it has less LCD to update x hundred
times/second. If they offloaded the LCD refreshing to another chip, the
speed increase would be significant.
Again, please keep in mind that this is not only speculation, it is
*wild* speculation. I just wanted to put it out and see if anyone has
compared the boards of both calcs (including under the LCD) and found
anything which could substantiate this.
-Adam
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