Question - UltraSatan and bad DMA chips

[Skarro]

Hello,

 

As many people are probably aware, there is a problem with some "bad" DMA chips in some of the earlier ST/STE/Mega-STE computers, which can cause problem when using devices like the UltraSatan.

 

With that in mind, I had a couple of questions:

 

1) Is there a way - via software - to determine whether the DMA chip in one's Atari is a good one or a bad one? Could someone who knows programming (and the ST hardware) come up with some kind of test that lets the user know whether they have a bad chip? Or does one have no option but to physically open the Atari up and remove the floppy drive to see the chip number printed on the IC?

 

2) If someone has a bad DMA chip and they want to replace it, how difficult is this to do? Is the DMA socketed, or do you have to de-solder all the pins individually?

 

Thanks!

[GadgetUK]

I thought it was only an early batch of ste's that had the bad DMA chip and that STFM's weren't affected? I've searched a bit to try and find a definitive list of models affected but just keep finding threads talking about the ste dma chip?

Edited January 18, 2013 by GadgetUK

[Skarro]

I thought it was only an early batch of ste's that had the bad DMA chip and that STFM's weren't affected? I've searched a bit to try and find a definitive list of models affected but just keep finding threads talking about the ste dma chip?

 

Yes, it seems you're correct about the ST part. I just re-checked Jookie's page about the DMA problem, and it only refers to STEs. Still, I have a Mega STE which I'm hoping should be OK (I bought it after it had already been on the market for a while), but just wanted to see if anyone knew of any "quick check shortcuts" before I go through the hassle of taking the computer apart to verify what's actually in there.

 

Thanks!

[jens]

I think it's about the 1040 (and maybe 520) STe models, not the Mega/STe.

Got a 520 STe with the faulty DMA chip here, and when serving the complete hard drive from an xcontrol/ sting/ ftp_serv floppy everything went ok.

I wasn't trying to unleash its ultimate powers which might have resulted in problems.

[ParanoidLittleMan]

Actually, in my Mega ST is not really good DMA chip - IMP brand, what I remember as little problematic overall - for instance IMP MMU chip can not handle 2.5 MB RAM.

Will problems appear, depends from attached adapter's speed too. And speed depends with UltraSatan from used SD card type, for instance. So, I think that we have something like very bad DMA chips (STE early revs.), and 'less bad' DMA chips - like IMP ones. When I replaced IMP with Atari DMA, Mega ST worked flawless, even at 1900KB/sec.

Edited January 19, 2013 by ParanoidLittleMan