Greenious wrote:To conclude,
it seems to me it is likely that Atari didn't get C398739-001 produced in time for the first STE's and gambled with the old ST-DMA.
Which seems to work fine at a glance, but with faster HW connected does not work well under stress with the STE chipset.
So technically there is no "bad" DMA, just bad combinations of DMA and STE.
This is an intriguing theory and it totally makes sense. However, that would imply that either the Atari branded DMA devices work only by chance (i.e. the fact they added the resistors and whatever on data lines is purely coincidental to this problem) or that they were aware of the problems since the beginning but for some reason the STE exposes this problem much more often.
What strikes me is that if either of this is true, why they had bothered to produce the new DMA chip -- all Atari DMA devices work on the STE with the old chip, nobody officially admitted anything so why bother?
C398739 which is DIP-40 and the PLCC-44 C398789 equivalent are both used in STE/MSTE/TT.
Ie, atari abandoned the ST specific DMAs, (CO25913 , C100110), with their newer machines even though it is pin compatible.
Even more plausible is that they didn't discover there was a slight problem with the ST-DMA in STE until actually launching the machine, and quietly replaced it, perhaps because the recall would be too expensive.
However, I have no doubt what so ever that Atari did indeed test CO25913 in STE extensively before launching the STE, albeit it is also likely they didn't test it with third-party hardware.
In any case, I have not in my experience met a lot of people with HDD problems that has been due to a "bad" DMA, I can easily count them on one hand. In many ways I do find this topic exagerrated, while at the same time I also think it has merit. It's a topic that people need to be aware of, at the same time I do find the hype around it a bit hysterical.
I remember it being discussed at BBS's at the time, and it does keep popping up at regular intervals here and elsewhere on the net. (Which also is a reason I decided to unlock the thread, since I know ppl will dig up this topic in 6 months, a year or so from now, and we already got a number of threads discussing this if you care to search the forum) And every time the topic resurface, the "problem" seem to grow...
Edit: In my guide thread I have put a collection of Atari Technical Bulletins, some of them refer to floppy drive problems, which might explain why some people have problems with that. Since the "dma bug" never, atleast not until recently, has been known to affext anything but harddrives...