[TI-H] Re: TI-89 HW2 overclocking
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[TI-H] Re: TI-89 HW2 overclocking
Shyam D. wrote:
>Don't certain srams have special commands? If this is true for the
>memory in the T-89 then it would be almost impossible to find suitable
>ram. It seems like TI wouldn't use any special ram like that on Graphing
>calculators for students, but its worth checking out just in case. If it
>doesn't have any special commands than everything should be ok. You
>should check the trigger voltages too. They might different in the ram
>Ti is using and the ram your looking at.
>
>
>Now, for the crux of my inquiry:
>Could the SRAM modules on the TI-89 HW2 be replaced with SRAMs from
>another
>manufacturer that have identical voltage/pinout/memory width/size
>characteristics,
>but have faster access times?
>
>One candidate I have found:
>Cypress CY7C62128V-55, has 45ns "write pulse width", giving theoretical
>max
>CPU
>speed of 22.2MHz.
>(datasheet: http://www.cypress.com/cfuploads/img/products/38-05061.pdf)
>
>
>Anyone more knowledgeable than I is welcome to comment on the validity
>of
>my
>assumptions and conclusions.
>
>
Another thing to do if you anyway are going into the calc, and replacing
the ram chip, is to cram in a 2MB chip instead of the 256K one.
or atleast 512 or something.
the memory area between 0 and 0x1fffff is reserved for ram, but only 0 -
0x3ffff is used, so it should be fairly simple.
Maybe find a chip that is as pin compatible as possible, and bend up the
pins not compatible and solder short wires from these.
I don't remember, is the ram repeated in this 2M area? if so, its even
better, no need to change the chip select wiring, just use the old one.
just add some more wires for the extra adress pins.
--Olle
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