BAD DMA - Myth or fact ?

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Re: BAD DMA - Myth or fact ?

Postby Maeke » Mon May 29, 2017 4:38 pm

one thing i can tell, you most likely won't find a 68hc0000 as genuine processor in the atari st line.

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Re: BAD DMA - Myth or fact ?

Postby crashman » Wed Jan 17, 2018 6:44 pm

Another STE with the "bad" DMA repaired with only a change on the CPU.

A friend of mine is happy after just changing the CPU for a 68HC000 and having zero SD corruption problems.

Thanks exxos for all you investigations and work.
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Re: BAD DMA - Myth or fact ?

Postby ijor » Wed Jan 17, 2018 6:59 pm

kodak80 wrote:Just an update from me. I have an STE which was corrupting the files on my Satandisk when I copied files to the drive from floppy. I have finally replaced the CPU with a MC68HC000FN8 and have just sucessfully copied a large amount of files around without seeing the corruption occur. :D


Btw, do you still have that setup?

I've been thinking that may be, may be, Jeff is right when he mentioned that the CMOS part might be not 100% compatible. There are a couple of undocumented issues on the 68000 that conceivable might behave different.

It would be interesting to test a few protections. War Heli comes to mind.

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Re: BAD DMA - Myth or fact ?

Postby czietz » Wed Jan 17, 2018 8:13 pm

ijor wrote:I've been thinking that may be, may be, Jeff is right when he mentioned that the CMOS part might be not 100% compatible. There are a couple of undocumented issues on the 68000 that conceivable might behave different.


Out of curiosity: can you provide more details -- or a link? I was also thinking of replacing the CPU in my STE by a 68HC000. If I do so, I would know what to look for...

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Re: BAD DMA - Myth or fact ?

Postby troed » Wed Jan 17, 2018 8:30 pm

I have two 68HC000 laying around for when I would find some use for them. I'll happily do the same. Since they do seem to solve the famous DMA-issue it would probably well worth the time :)

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Re: BAD DMA - Myth or fact ?

Postby kodak80 » Wed Jan 17, 2018 8:51 pm

ijor wrote:
kodak80 wrote:Just an update from me. I have an STE which was corrupting the files on my Satandisk when I copied files to the drive from floppy. I have finally replaced the CPU with a MC68HC000FN8 and have just sucessfully copied a large amount of files around without seeing the corruption occur. :D


Btw, do you still have that setup?

I've been thinking that may be, may be, Jeff is right when he mentioned that the CMOS part might be not 100% compatible. There are a couple of undocumented issues on the 68000 that conceivable might behave different.

It would be interesting to test a few protections. War Heli comes to mind.

Yes, I still have the STE which I swapped the CPU. I would be happy to do some more testing to help confirm if the CMOS chip is not 100% compatible. I have an SCP and KF flux board and can duplicate most disks if you have the images.
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Re: BAD DMA - Myth or fact ?

Postby ijor » Thu Jan 18, 2018 1:29 am

czietz wrote:Out of curiosity: can you provide more details -- or a link? I was also thinking of replacing the CPU in my STE by a 68HC000. If I do so, I would know what to look for...


I don't have much details. It is just a hunch. Most 68000 undocumented issues are by design, or otherwise they are an obvious result of the implementation. I would expect most of them were intentionally preserved when they made the conversion to CMOS. But a couple of issues are just by chance. It is not much different than the undocumented opcodes on the NMOS 6502. Not that the 68000 has any undocumented instruction. But analogously, they are the result of specific electrical characteristics of the die.

It is mostly about the finer details of the bus error behavior. And I seem to remember that War Heli, the original copy protected version, depends on this. It was several years ago when I checked the protection. Of course it is not the only title, but it is the only one I can recall right now.

Again, it is just a hunch. It might be the CMOS version has no compatibility problems. But it would be very interesting to perform a few tests.

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Re: BAD DMA - Myth or fact ?

Postby ijor » Thu Jan 18, 2018 3:56 am

kodak80 wrote:Yes, I still have the STE which I swapped the CPU. I would be happy to do some more testing to help confirm if the CMOS chip is not 100% compatible. I have an SCP and KF flux board and can duplicate most disks if you have the images.


SCP image of War Heli should be on retrobackup.com according to this post:
http://www.atari-forum.com/viewtopic.ph ... 75#p277315

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Re: BAD DMA - Myth or fact ?

Postby joska » Thu Jan 18, 2018 10:04 am

Basically you're compensating for a device that does not really work in the STE design by replacing another part with a part that the STE isn't designed for :) That's really not a fix, but a workaround. But if it works, then this does not matter. The most important thing is that it works.

I have a 16Mhz 68hc000, but it does not work in my STE's. Maybe the CPU is broken, I have just ordered a few more so I can test this properly.
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Re: BAD DMA - Myth or fact ?

Postby ijor » Fri Jan 26, 2018 8:25 pm

kodak80 wrote:Yes, I still have the STE which I swapped the CPU. I would be happy to do some more testing to help confirm if the CMOS chip is not 100% compatible. I have an SCP and KF flux board and can duplicate most disks if you have the images.


Bump ... Just curious, were you able to run any test?

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Re: BAD DMA - Myth or fact ?

Postby kodak80 » Fri Jan 26, 2018 8:53 pm

ijor wrote:
kodak80 wrote:Yes, I still have the STE which I swapped the CPU. I would be happy to do some more testing to help confirm if the CMOS chip is not 100% compatible. I have an SCP and KF flux board and can duplicate most disks if you have the images.


Bump ... Just curious, were you able to run any test?

Sorry, had to check which STE had the chip.

Have just dug out the STE, created the War Heli disk from the SCP image and booted it up. I have only played the first level and it works fine with the new CPU. :D
Last edited by kodak80 on Fri Jan 26, 2018 8:57 pm, edited 1 time in total.
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Re: BAD DMA - Myth or fact ?

Postby kodak80 » Fri Jan 26, 2018 8:56 pm

Now I have the STE on my desk, let me know which other games I should test. As long as the SCP is available I can duplicate the disk and test.
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Re: BAD DMA - Myth or fact ?

Postby ijor » Sat Jan 27, 2018 6:52 pm

kodak80 wrote:Sorry, had to check which STE had the chip.
Have just dug out the STE, created the War Heli disk from the SCP image and booted it up. I have only played the first level and it works fine with the new CPU. :D


Many thanks. If it was the original copy protected version of War Heli, then my guess is that this test is quite conclusive. Tell me please the length of the SCP file to verify it's the same version I am talking about.

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Re: BAD DMA - Myth or fact ?

Postby kodak80 » Sat Jan 27, 2018 7:57 pm

ijor wrote:
kodak80 wrote:Sorry, had to check which STE had the chip.
Have just dug out the STE, created the War Heli disk from the SCP image and booted it up. I have only played the first level and it works fine with the new CPU. :D


Many thanks. If it was the original copy protected version of War Heli, then my guess is that this test is quite conclusive. Tell me please the length of the SCP file to verify it's the same version I am talking about.


Here is a link to the SCP dump I used:

https://mega.nz/#!xiIiERhI!yTMgdBWOasQk ... FujYCq2fQU

It was taken from retrobackup.com a while ago. Size of the file is 45,737kb
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Re: BAD DMA - Myth or fact ?

Postby ijor » Sun Jan 28, 2018 2:17 pm

kodak80 wrote:Here is a link to the SCP dump I used ... It was taken from retrobackup.com a while ago. Size of the file is 45,737kb


Can't test it thoroughly, but seems it is the same version I analyzed at the time. If that protection works ok on the CMOS CPU, then probably it's indeed 100% compatible.

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Re: BAD DMA - Myth or fact ?

Postby Lando_C » Thu Feb 15, 2018 9:02 pm

IF you read teh article carefully, it says there are only a hundrd or so machines affected in the hands of users.. That suggests to me a bad batch of chips, not a whole series, am I right?
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Re: BAD DMA - Myth or fact ?

Postby dlfrsilver » Sat Feb 17, 2018 2:52 pm

to give you an answer, i would say that all the STE made in 1989,1990 are plagued with this problem. The STE machines made from 1991 don't have the problem. Those models have a finalised hardware (read : with no patches made at the factory).
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Re: BAD DMA - Myth or fact ?

Postby Frank B » Sun Feb 18, 2018 12:11 am

dlfrsilver wrote:to give you an answer, i would say that all the STE made in 1989,1990 are plagued with this problem. The STE machines made from 1991 don't have the problem. Those models have a finalised hardware (read : with no patches made at the factory).


Yet I have a 1989 model which is fine with ultrasatan and any hard disk. Totally rock solid 1.6 machine. It's so old the machine has EPROMS in it instead of ROMS.

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Re: BAD DMA - Myth or fact ?

Postby Cyprian » Sun Feb 18, 2018 1:07 am

dlfrsilver wrote:to give you an answer, i would say that all the STE made in 1989,1990 are plagued with this problem

I would not agree with that. My STE works flawless with CosmosEx and Ultrasatan. It is very early STE with separated BLiTTER.
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Re: BAD DMA - Myth or fact ?

Postby Frank B » Sun Feb 18, 2018 2:19 am

The press at the time said it was limited to 1040 STe machines. I had my PSU reconditioned on my 520STE.

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Re: BAD DMA - Myth or fact ?

Postby dlfrsilver » Mon Feb 19, 2018 7:39 am

I have 1 520 STE, and 2 1040 STE. The 520 and the 1st 1040 were made in 1989, 1990. The 3rd machine, a 1040 STE, was made in 1991, and is the only one working correctly straight out of box with my ultrasatan.

The difference hardware wise, is that the one from 1989 and 1990 have the beta motherboards with factory patches. Those 2 are failing with any hard drive connected. The 1991 STE works perfectly :)
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Re: BAD DMA - Myth or fact ?

Postby Frank B » Mon Feb 19, 2018 6:40 pm

dlfrsilver wrote:I have 1 520 STE, and 2 1040 STE. The 520 and the 1st 1040 were made in 1989, 1990. The 3rd machine, a 1040 STE, was made in 1991, and is the only one working correctly straight out of box with my ultrasatan.

The difference hardware wise, is that the one from 1989 and 1990 have the beta motherboards with factory patches. Those 2 are failing with any hard drive connected. The 1991 STE works perfectly :)


Have you checked the PSUs? Every STe I've owned needed the PSU bridge rectifier fixed by Simbo.

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Re: BAD DMA - Myth or fact ?

Postby tzok » Thu Feb 22, 2018 1:06 pm

My STE is from 1989 or 90, don't know exactly, but this is the early version with a wire-patches on the motherboard. I remember it making a garbage from floppy disk FAT after longer work. Now I turn it occasionally, but have Megafile and it did never do anything bad to it. Yet I have replaced the original PROMs to Flash EPROMs, and later also the CPU to the CMOS version (actually this CPU was used in the ST series by factory - in the Atari STacy).

I have not recapped my STE PSU, as all the caps look ok. Once I did a recap of my collegue's STFM PSU, but after testing removed caps, they were in better condition (in terms of ESR) than replacement ones I used.


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