exxos's Atari, Amiga & retro forum

To get my STFM to work with both the UltraSATAN and the TF536 I had to change the DMA chip. The original chip wasn't strong enough to drive the lines. It would also cause the floppy to misbehave.

stephen_usher wrote: 02 Oct 2022 22:42 To get my STFM to work with both the UltraSATAN and the TF536 I had to change the DMA chip. The original chip wasn't strong enough to drive the lines. It would also cause the floppy to misbehave.

This is why you put 10k sils on the DMA data bus. Most chips have very poor pull up current or simply none at all. Generally all chips can pull down just fine. But not drive to 5v levels very well.

I did try that but it didn't work. I'm not sure that the DMA could pull down hard enough. I got worse with time, seemingly the UltraSATAN causing damage by being able to source more current than the DMA could handle.

stephen_usher wrote: 02 Oct 2022 23:10 I did try that but it didn't work. I'm not sure that the DMA could pull down hard enough. I got worse with time, seemingly the UltraSATAN causing damage by being able to source more current than the DMA could handle.

I remember your troubles. I can't remember how far that io investigation got now. But indeed there are multiple ways the DMA circuit can fail. I was just making sure its noted that while changing the DMA chip may, or may not work, its not generally the route cause of issues. I just don't want people to start changing random chips unless there is a good reason to.

In this thread I think he said it works without the ST536. IIRC @PhilC fitted a ST536 into a mega ? Though megas are generally the worst machines for stability.

It does also make me wonder what chips @ottifant011 has in his machine ? IMP chips are known to not help matters. Also I assume you removed the blitter patch and not tried to bodge it back in with the ST536 installed ? Also removed MB ROMs when running the ST536 ?

Thanks for all the tips
I took a few pictures

What is the black wire ?

Also you know when you remove the blitter patch there is a track to repair under the CPU.

I took a few pictures of where the black cable goes
how do I remove the bitter patch and what should be repaired under the cpu are there any pictures or an FAQ

ottifant011 wrote: 03 Oct 2022 10:05 how do I remove the bitter patch and what should be repaired under the cpu are there any pictures or an FAQ

Just take the motherboard out and look on the bottom under the CPU.. there is a cut track.. Just repair it.. Remove the little board off the CPU.. you probably do not need it anyway, Unless you have a really old blitter.

ok interruption found and bridged.
does u5 have to be removed too?
exactly once he booted up with the ultrasatan

ottifant011 wrote: 03 Oct 2022 11:00 does u5 have to be removed too?

To save me hunting, which exactly is U5 ?

ottifant011 wrote: 03 Oct 2022 11:00 exactly once he booted up with the ultrasatan

Good progress then!