Closed Atari STe Good DMA Chip C398739-001 40pin DIP Chip Wanted

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Paradroid90

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HI All

I know it is a long shot but I am looking for a 40pin DIP DMA Chip for the Atari STe

Due to having read and writing issues with my Ultra Satan it needs to be the mythical C398739-001 DMA please

Thanks in advance :)
 
you might be wrong,

the BAD DMA chip is possibly a myth and not related to the chip but noise on the bus lines.

check the below link

here is an excerpt

I had a couple of emails from 'Oliver de Font' who has several STE's all of which suffer from DMA issues with ultrasatan. He did as I suggested previously in changing the CPU and he reported back it solved his DMA issues. He since emailed me saying the same fix also worked on another STE. His STE's all have the -38 DMA.


So why does the CPU "fix" DMA issues ? Well like I said from the start, noise on the bus. In fact after investigation the problems mostly seem to be generated from near the CPU. Poor grounding on the CPU is causing huge voltage spikes near the DMA IC. Such spikes can latch up logic internally in the DMA and that is likely what happens.

Changing the CPU to a HC type pushes less current though the ground connections on the motherboard and the voltage "bounce" gets greatly reduced. Once this problem is reduced, the DMA no longer "sees" these screwy voltages and it behaves perfectly.

https://www.exxoshost.co.uk/atari/last/DMAfix/


I installed a 68HC000 in my old A500+ as it was having issues with certain Eproms for kick 3.1, turns out the HC model has "built in" pull up resistors that commodore cheaped out on ( the holes around the cpu )

the Atari STE might have similar issues with noise on the bus causing all kinda issues like your Satan
 
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Thanks Sardine. Already had someone complete all the fixes and managed to get most of the HD functionality but been advised to get the "Good" DMA to see if it will allow writing in one mode :)
 
thats the whole point, its not a bad dma its another issue in your ste, bad dma is a myth

So yet again the "DMA myth" is busted and "bus noise" has been proven once again to be the issue. So I urge people who have DMA issues to change the CPU to a HC type, or at the never least, use a SGS CPU and not the Motorola ones. Then see how it goes and report back to me your findings!
 
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