Re: TI-H: RAM expanders?

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Re: TI-H: RAM expanders?

David Patnode wrote:

> Hey all! I'm new to this list, so please forgive me if this is a FAQ! :) I'm
> taking a digital electronics class in high school, and for the semester
> project I would like to build a RAM expander for my ti-85. Now, the last I
> heard was that plans were still under construction for them, but then again,
> the last time I checked was months and months ago, so I'm hoping there's
> been some progress since then.
>
> What I'm looking for is plans (and suppliers, if some of the parts are hard
> to find) for a ram/(memory) expander that I can simply plug into the I/O
> port. I would like to be able to access it as if it was "real" ram, as
> opposed to copying things between the expander and the TI's memory, but
> that would just be a convience, not set requirement. Since I'm just learning
> digital, I don't feel up to the task of designing such a project myself, nor
> making a bunch of modifications to some "beta" design. Also, I'm hoping the
> device can be fairly small. If this type of information/plans is available,
> please let me know! Thank you!!!

Oh dear...

Well, the only memory expander that has ever been shown
to work on the TI-85 is Mel Tsai's Expander SF. However,
these are out of production since the chips were discontinued
There is still someone on the list trying to sell 3 of them, so you
may want to contact him.

Secondly, it is nearly impossible to add a "RAM expander"
to the TI-85; The ESF is actually a high density non-volatile
 serial flash EEPROM -- Not RAM in any sense of the word.
If you wish to have it directly accessible, you're going to need
to do some serious hardware magic, not to mention literally
rewrite a ROM chip... Essentially, you'd have to make a TI-85
into a hacked TI-86 in a TI-85 case. Certainly, I think that's
beyond the abilities of anyone on this list, except, maybe,
for Mel Tsai himself. ;-)

Finally, I don't know the details of this project, but it seems
to me that designing something and then constructing it from
the ground up would be much more beneficial and enjoyable.
Building something you know will work, but getting something
you're not sure about to work the very first time is a great feeling.

I can't resist adding a cheap plug.. I've made a TI-92 memory expander
out of parts that are still availible. An interesting project for you would
be to adapt it to work with the 85 (the hardware is done, but you would
need to write the driver software). Not to mention, that would save me
from getting off my slothful butt. ;-)

Mel Tsai's page is linked of of mine, the later of which is at
http://www.flash.net/~bryanr/extend/

Bryan Rittmeyer
bryanr@flash.net
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