STe - Bad DMA Chip

Troubles with your machine? Just want to speak about the latest improvements? This is the place!

Moderators: Mug UK, Zorro 2, Greenious, spiny, Moderator Team

siriushardware
Atari Super Hero
Atari Super Hero
Posts: 502
Joined: Thu Aug 21, 2014 7:55 pm
Location: UK

Re: STe - Bad DMA Chip

Postby siriushardware » Sun Sep 22, 2019 9:20 am

"Myth".

I think that's a slight overstatement. There obviously is a problem for some machines which originally had a 'normal' CPU and a 'Bad' DMA fitted, when used in conjunction with certain HDD-like devices such as UltraSatan.

Originally most people were able to fix this by replacing the 'Bad' DMA with a 'Good' DMA but since these devices were Atari-STe specific they were not always easy to come by. Then it was discovered that (as you have said) the problem can also often be fixed by retrofitting a CMOS version of the CPU, which is a much more generic, widely available component.

So, anyone thinking they have a 'Bad DMA' problem should probably try changing the CPU to a CMOS type first. It obviously worked for you.

joska
Hardware Guru
Hardware Guru
Posts: 4491
Joined: Tue Oct 30, 2007 2:55 pm
Location: Florø, Norway
Contact:

Re: STe - Bad DMA Chip

Postby joska » Sun Sep 22, 2019 5:57 pm

bulga wrote:I follow this invsestigation: https://www.exxoshost.co.uk/atari/last/DMAfix/index.htm, I've changed the cpu with a Freescale 68HC000.
Problem solved. Bad DMA is a mith.


Have you read the last couple of pages of this thread? It would be interesting to know how We Were and {closure} works on your HC-equipped STE.
Jo Even

VanillaMiNT - Firebee - Falcon060 - Milan060 - Falcon040 - MIST - Mega ST - STM - STE - Amiga 600 - Sharp MZ700 - MSX - Amstrad CPC - C64

User avatar
dlfrsilver
Atari God
Atari God
Posts: 1483
Joined: Mon Jan 31, 2005 1:41 am
Contact:

Re: STe - Bad DMA Chip

Postby dlfrsilver » Mon Sep 23, 2019 7:26 am

tzok wrote:Have anyone read this:
We received trouble reports from a few STe's used in combination with a hard drive. The problem that arose was the mutilation of data, directories or the presence of faulty sectors during the work. These effects result from the fact that some brands of SIMM's can influence the line "Acknowledge". The problem can be solved by placing a 30PF capacitor on the CPU (U100) between pins 13 and 16. Then the value of P100 should be decreased to 1K2. This can be done by placing a "second" resistor pack "in parallel with the first while retaining the same value of 2K2. Finally you must connect the pin 9 of the P105 to the pin 1 of the U401. Note that this fitting is existing on the circuit. Check its operation with a universal multimeter! We have written a program of tests specifically designed to control the communication of hard disks. This program works on all Toss systems on ST and TT computers. This program is called HDCHECK and is found in our ATARI-Net Bulletin Board SIG15, under Nos (03473-77584 and 77376) HDCHECK generates "directories", creates the "files" to eliminate them afterwards and check after each creation if the system has received the correct information in the "directories" and the "FATs" This program is especially recommended for burn-in tests.


This is from Atari STe technical bulletin, found at: http://gossuin.be/index.php/520-et-1040-stx (http://gossuin.be/images/schemasatari/N ... E%20FR.pdf)

Best Tech Tips suggested a 30 pF capacitor between pins 2 and 4, but this has no sense, as these are two databus lines (D1 and D3)... the Atari Technical Bulletin mentions pins 13 and 16 which are XBR (Bus Request) and GND, and this has much more sense.

Image


Yes, i read that. Atari was well aware of this problem. But they also say in french that instead :

"The problem can be solved by placing a 30PF capacitor on the CPU (U100) between pins 13 and 16. Then the value of P100 should be decreased to 1K2. This can be done by placing a "second" resistor pack "in parallel with the first while retaining the same value of 2K2. Finally you must connect the pin 9 of the P105 to the pin 1 of the U401."

You must replace the DMA chip to solve the problem. (Replace DMA chip 4140 by STE DMA in english in the PDF).
Now SPS France representative since the 19th of June 2014. Proud to be an SPS member !

User avatar
dlfrsilver
Atari God
Atari God
Posts: 1483
Joined: Mon Jan 31, 2005 1:41 am
Contact:

Re: STe - Bad DMA Chip

Postby dlfrsilver » Mon Sep 23, 2019 7:49 am

Also remember this from Best Inc, an info coming also from Atari :

https://www.exxoshost.co.uk/atari/last/ ... 5QDl0RS58s
Now SPS France representative since the 19th of June 2014. Proud to be an SPS member !

tzok
Captain Atari
Captain Atari
Posts: 187
Joined: Fri Jun 30, 2017 7:22 pm
Location: Bielsko-Biala, PL
Contact:

Re: STe - Bad DMA Chip

Postby tzok » Mon Sep 23, 2019 1:41 pm

Yes, I was referring exactly to this bulletin - capacitor between CPU pins 2 and 4 has no sense, original Atari bulletin mentions pins 13 and 16, and these do have sense.

tzok
Captain Atari
Captain Atari
Posts: 187
Joined: Fri Jun 30, 2017 7:22 pm
Location: Bielsko-Biala, PL
Contact:

Re: STe - Bad DMA Chip

Postby tzok » Thu Sep 26, 2019 11:45 am

On my HC STe We Were @ works ok, however it displays some garbage on the left border in the full screen distorter, same with {closure}:
Image

On the other hand, the Atari ST 32768 Colour Showdown seems to work just fine:
Image Image Image

Jeff_HxC2001
Captain Atari
Captain Atari
Posts: 362
Joined: Fri Sep 21, 2007 7:35 pm
Location: Paris - France
Contact:

Re: STe - Bad DMA Chip

Postby Jeff_HxC2001 » Fri Oct 04, 2019 6:19 am

bulga wrote:
blackpanther wrote:Hi all!

Just joined the Forum as I got my first Atari STe last month and was hoping someone here could help me. I recently found out that my STe has a bad DMA chip and with the ultrasatan soon to be finished I want to try and sort this out before I recieve it.

I do have a STFM and was wondering if it was possible to use the DMA chip from that? If not does anyone no where I can buy one?

Thanks
Mark


I follow this invsestigation: https://www.exxoshost.co.uk/atari/last/DMAfix/index.htm, I've changed the cpu with a Freescale 68HC000.
Problem solved. Bad DMA is a mith.


I agree that this "Bad DMA" story is mostly a myth, or more precisely that the DMA IC itself is probably not the root cause of the issue.
But i have no trust with the 68HC000 replacement trick too : It seems to generate strange effects with some demos. You just appears to "fix" the dma issue but this broke something else...

The probable root cause of all these issues is maybe that the pcb layout is just bad ?... An Hyperlynx pcb simulation/analysis may be interesting ;)

siriushardware
Atari Super Hero
Atari Super Hero
Posts: 502
Joined: Thu Aug 21, 2014 7:55 pm
Location: UK

Re: STe - Bad DMA Chip

Postby siriushardware » Sat Oct 05, 2019 3:53 pm

It doesn't actually matter whether the 'Bad DMA' scenario is a myth or not, if changing the 'Bad DMA' to a 'Good DMA' fixes people's DMA problems, and in many cases it has.

In the vast majority of cases the people who have done this do not care why it fixes the problem as long as it does.

Understanding why it fixes the problem is for people who are on a whole different higher level. (I am not one of those people).

ijor
Hardware Guru
Hardware Guru
Posts: 3919
Joined: Sat May 29, 2004 7:52 pm
Contact:

Re: STe - Bad DMA Chip

Postby ijor » Mon Oct 07, 2019 7:24 pm

I agree with siriushardware that defining this as a myth is an overstatement. Is is true that the problem seems to be rather complex, and probably there is a combinations of issues, apparently including indeed, pcb layout. But in many cases replacing the "bad DMA" fixes the problem. Is is true that usually there are other possible fixes, like installing a CMOS CPU. And sometimes even just replacing the DMA chip doesn't help. Yet, a "good DMA" works in many cases where the "bad" does not.
Fx Cast: Atari St cycle accurate fpga core

Jeff_HxC2001
Captain Atari
Captain Atari
Posts: 362
Joined: Fri Sep 21, 2007 7:35 pm
Location: Paris - France
Contact:

Re: STe - Bad DMA Chip

Postby Jeff_HxC2001 » Mon Oct 07, 2019 7:46 pm

siriushardware wrote:In the vast majority of cases the people who have done this do not care why it fixes the problem as long as it does.


Quite dangerous, since you don't really know what cause the issue ;)

Jeff_HxC2001
Captain Atari
Captain Atari
Posts: 362
Joined: Fri Sep 21, 2007 7:35 pm
Location: Paris - France
Contact:

Re: STe - Bad DMA Chip

Postby Jeff_HxC2001 » Mon Oct 07, 2019 7:59 pm

ijor wrote:I agree with siriushardware that defining this as a myth is an overstatement. Is is true that the problem seems to be rather complex, and probably there is a combinations of issues, apparently including indeed, pcb layout. But in many cases replacing the "bad DMA" fixes the problem. Is is true that usually there are other possible fixes, like installing a CMOS CPU. And sometimes even just replacing the DMA chip doesn't help. Yet, a "good DMA" works in many cases where the "bad" does not.


Since changing the CPU seems to fix the issue, we can also call this the "Bad CPU Chip issue".
or
Since this issue appears to affect some drive models then we can also call this the "Bad ACSI drives issue".
or
Since it appears that delaying/filtering some data and/or control signals appears to fix the issue we can call it the "Bad PCB issue".

What i call "myth" for the moment is claiming that the only cause is the DMA. As you said this is more complex and the DMA/HDD issues may be just a side effect of something else...

ijor
Hardware Guru
Hardware Guru
Posts: 3919
Joined: Sat May 29, 2004 7:52 pm
Contact:

Re: STe - Bad DMA Chip

Postby ijor » Mon Oct 07, 2019 8:48 pm

Jeff_HxC2001 wrote:What i call "myth" for the moment is claiming that the only cause is the DMA. As you said this is more complex and the DMA/HDD issues may be just a side effect of something else...


Again, I suspect (can't say I am 100% sure), it is not exactly something else, but a combinations of factors. If it was just something else, then replacing the DMA wouldn't help, and many times it does. As I mentioned some time ago, it might have to do with the internals designs of the DMA chip. All the ST chipset has some async logic, at least the older generations, but DMA is the worst. Also usually depends on the specific ACSI device. But yes, it is certainly not the DMA chip alone.
Fx Cast: Atari St cycle accurate fpga core

siriushardware
Atari Super Hero
Atari Super Hero
Posts: 502
Joined: Thu Aug 21, 2014 7:55 pm
Location: UK

Re: STe - Bad DMA Chip

Postby siriushardware » Tue Oct 08, 2019 10:40 pm

Jeff_HxC2001 wrote:
siriushardware wrote:In the vast majority of cases the people who have done this do not care why it fixes the problem as long as it does.


Quite dangerous, since you don't really know what cause the issue ;)


Not really, if the original fault (hard drive device corruption) is fixed and the machine exhibits no new side effects at all. That would be a satisfactory result for nearly anyone.

joska
Hardware Guru
Hardware Guru
Posts: 4491
Joined: Tue Oct 30, 2007 2:55 pm
Location: Florø, Norway
Contact:

Re: STe - Bad DMA Chip

Postby joska » Wed Oct 09, 2019 8:36 am

siriushardware wrote:Not really, if the original fault (hard drive device corruption) is fixed and the machine exhibits no new side effects at all. That would be a satisfactory result for nearly anyone.


I can't see the danger in replacing the "bad" DMA with the "good" DMA, since that's what Atari did themselves. I have not heard of any side effects of this (except that it doesn't always fix the problem, which in itself suggests that the problem is more complex than a single chip), but I have personally experienced negative sideeffects in replacing the CPU. So I know what my preferred fix would be.
Jo Even

VanillaMiNT - Firebee - Falcon060 - Milan060 - Falcon040 - MIST - Mega ST - STM - STE - Amiga 600 - Sharp MZ700 - MSX - Amstrad CPC - C64

User avatar
Marcer
Atarilegend
Atarilegend
Posts: 4187
Joined: Wed Mar 10, 2004 6:21 pm
Location: sweden
Contact:

Re: STe - Bad DMA Chip

Postby Marcer » Sat Jan 04, 2020 4:38 pm

Hi

While browsing alot of files for gamedvd. I found this tool.
Not tested. But I think this is a French DMA TEST program.
You do not have the required permissions to view the files attached to this post.
- Atari ST/FM/E - Mega sTe - Portfolio - Falcon 030 FX 3 in 1 -- Atari 7800/Lynx/Jaguar -
- FTP... Ask for info
- Atari Legend (Games all-a-round)
- Paradize (Chip Music)
- Elite (Atari Softs)
- The Legion (Demos)
- Alive Maggie Team
_/|\_YM-RockerZ_/|\_


Social Media

     

Return to “Hardware”

Who is online

Users browsing this forum: No registered users and 9 guests

cron