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TI99/4A ROMS High Byte and Low Byte

4 replies to this topic

#1 repetto74 OFFLINE  


    Chopper Commander

  • 149 posts

Posted Wed Oct 25, 2017 2:16 PM



I have successfully managed to found what was wrong on a faulty TI99/4a. One of the two console ROM is bad and need to be replaced. I do have already a spare eprom to be programmed (2532) but can someone point me out to which ROM is the High Byte and which one is the Low Byte? The faulty rom is located left side from the two scratchpad rams and dame orientation. :?  :)





#2 ClassicGMR OFFLINE  



  • 1,063 posts
  • Location:Northeastern U.S.

Posted Thu Oct 26, 2017 8:28 AM

Nice to see you are still trying to save this TI. :)


Someone IS reading your posts! (Unfortunately I just have no information to give.)

#3 repetto74 OFFLINE  


    Chopper Commander

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  • 149 posts

Posted Thu Oct 26, 2017 2:00 PM

Hi Classic GMR


Thanks :-). I have tested the ROMS coming from the working TI99 and swapped them to the faulty board and magic the TI99/4a will boot up ! :-) So it is just a matter of programming a 2532 eprom with the ROM code and I am good to go.

Anyway I did find that the ROM position is the U611 and I do have the BIN file for it. :-)

#4 repetto74 OFFLINE  


    Chopper Commander

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  • 149 posts

Posted Wed Nov 8, 2017 12:31 PM

So finally a fixed TI99/4A :-D. Burned the TMS-2532A and installed it into the TI99 + pull-up resistor between pin 21 and 24 for the CS enabled. 

All is working good now ! 

#5 Ksarul OFFLINE  


    River Patroller

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Posted Sat Nov 11, 2017 12:56 PM

Excellent! I'm glad you figured out which ROM was which. You probably could have taken the good one and compared the contents to each of the two half files in a hex editor and that would have told you which half was good (High or Low byte)--and by default identify the bad ROM as the High or Low byte.

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