exxos's Atari, Amiga & retro forum

Hi everyone, I need help with my Atari STE.
I bought a French Atari 520STE. I programmed 1.62 tos in Spanish. I added 4 MB of RAM. I replaced the floppy drive. Everything's fine.
The problem I have is that when I buy an ACSI2STM, it doesn't work (it works perfectly on another Atari).

This unit has a C025913-38 DMA chip, so I investigated possible solutions.
I replaced the power supply capacitors, and it started showing the folders, but it gave me a lot of errors.
I decided to buy the DMA ST converter. And now I can load games in GemDrive mode, but no .img files will start.
Something curious is that the Atari only detects the ACSI2STM if I raise the power supply voltage to +12.70V... it's strange.


Any advice? What else can I do?
Thank you very much

What PSU do you have? I have a few ST's and one refused to work with ACSI2ST even after a PSU recap. I changed out the caps again to the spec Exxos suggested in his PSU blogs and that fixed the problem. I installed the DMA fix as well, made no difference. Are you running the ACSI2STM off the ST or externally?

You may want to look at the mandatory fixes too: Mandatory Fixes

If you don't want to have any trouble, simply install a STE C398739-001A = STE DMA chip (U300) ...

frank.lukas wrote: 14 Jun 2025 17:48 If you don't want to have any trouble, simply install a STE C398739-001A = STE DMA chip (U300) ...

:sigh:

Again not true. Myself and others have documented many times its not a silver bullet fix. In some of my tests that chip actually made things worse.

The DMA bug fix adapter made no difference on mine. All my ICD links and SCSI drives worked fine, ACSI2STM did not till it was upgraded to exxos specs, pretty sure it was a Mitsumi PSU. I socketed the DMA so I was able to easily test and the stock PSU was not up to the job for some reason.

atari030 wrote: 16 Jun 2025 04:27 The DMA bug fix adapter made no difference on mine. All my ICD links and SCSI drives worked fine, ACSI2STM did not till it was upgraded to exxos specs, pretty sure it was a Mitsumi PSU. I socketed the DMA so I was able to easily test and the stock PSU was not up to the job for some reason.

That adapter thing sold on EvilBay? I think the problem is that messing with the DMA chip is treating the symptom all the time not the cause.

Good to know your got working again anyway :thumbup:

frank.lukas wrote: 14 Jun 2025 17:48 If you don't want to have any trouble, simply install a STE C398739-001A = STE DMA chip (U300) ...

In some case, it's not enough to fix the problem. Some people will fix their machine with this and others will not get ride of the "bug".

regarding my own STEs, replacing yhe DMA chip alone was not enough, i had to replace the CPU with a low current consumption to end "the bug" one end for all.

exxos wrote: 16 Jun 2025 09:22
That adapter thing sold on EvilBay? I think the problem is that messing with the DMA chip is treating the symptom all the time not the cause.

Good to know your got working again anyway :thumbup:

That's the one, I'm sure it works but just because you have DMA issues doesn't mean its the DMA chip bug, so yes, I think you are right. Pretty sure I have an HC cpu in that machine too. Another chap on Atari forum had the same problem, he upgraded his PSU and voila as well.

I have three STE's and only one exhibited problems. After that experience if I see issues like that, PSU first, HC second and DMA last would be how I would handle it.

atari030 wrote: 17 Jun 2025 06:57 but just because you have DMA issues doesn't mean its the DMA chip bug,

Yes exactly. There are multiple causes which many never seem to realise. The DMA chip is the default "go to" for all and its simply not the case a lot of times.

My early STEs all "failed" after I upgraded the 4MB. I didn't know back then it was the PSU failing causing the problems.

so yes, I think you are right. Pretty sure I have an HC cpu in that machine too. Another chap on Atari forum had the same problem, he upgraded his PSU and voila as well.

Yeah trying to fix a 40year old machine without doing basic stuff like check the psu first is pretty reckless.

I have three STE's and only one exhibited problems. After that experience if I see issues like that, PSU first, HC second and DMA last would be how I would handle it.

:bravo: Welcome to sanity ;)

But don't forgot Atari changed the pullups on later revisions. They are a factor in DMA issues also.

I did a new page on all this about a year ago to correlate the mods better..

https://www.exxosforum.co.uk/atari/last/DMASG/index.htm