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TOS replacement chips for the Atari 520 ST


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I don’t think this is the right area but I can’t seem to find one. I purchased some 70 ns trips to use as my new 1.4 rainbow TOS. I went through them three or four times and I cannot get anything to pop up on the desktop in fact, the desktop itself or at Pop up.I don’t think this is the right area but I can’t seem to find one. I purchased some 70 ns trips to use as my new 1.4 rainbow TOS. I went through them three or four times and I cannot get anything to pop up on the desktop in fact, the desktop itself or not pop up. Are the 70 ns chips too fast for the Atari??? Thanks for any help!

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Can you please explain what chips you are trying to use (I assume that's what you mean by trips ?),

did they come pre-programmed or are you burning them yourself ?

 

TOS ROM's are split into high/low addressing, so the TOS needs to be split between them, I assume

as it's a 520ST then it's using 6 chips in which case

3 of them go in the high address sockets, the other 3 in the low. Get any in the wrong slot

and it will not work.

 

I don't think the chip speed would be a problem, that's the max speed it will run at, it won't

affect access if running slower.

Edited by TGB1718
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You will need two or six chips, most 520ST's use 6 chips.  The EPROM type you need is 27C256.  You also need a proper split ROM image to program them correctly, then you need to insert them in the correct sockets.  Lots can go wrong here.

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