The BAD DMA Chip myth

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Official Ninja
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Re: The BAD DMA Chip myth

Post by Official Ninja »

joska wrote:The "myth" has it that only early STE's had this problem. They had TOS 1.06 fitted, so if your STE was originally fitted with 1.62 I think you should be safe.

http://members.optusnet.com.au/~colbee1/DMAFAULT.HTM
Thanks, I did open the case today and saw the good DMA chip in there.

I wanted to try TOS2.06 in this STe so I borrowed the chips from a spare Mega STe I have.

I had to move the resistor jumpers and boke one. I tried just jumpering with a wire but it didnt seem to work.
I'll have to stop by the electronics store tomorrow and see if the have any. Tan with a single black stripe. I think these are zero ohm jumpers?

Back on topic, I was glad to see the good dma chip. I got a SatanDisk with this STe and Im learning to use it. Glad I dont have to worry about the dma chip.
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Re: The BAD DMA Chip myth

Post by oehansen »

alexh wrote:
oehansen wrote: If as you say (and I don't doubt it) that the problems of the "bad DMA" chip can be worked around. And if they can be worked around in firmware (or small mods to the PCB) with UltraSatan... then surely this is the perfect starting point? Plus it already has users.
I sincerely hope you are right, I really want to be talking bollox ... because I love this machine. And I love the FireBee ...

Maybe, I am a bit too ambitious ... because I wanna go forward, fast forward. I wanna have the Atari be POSIX compliant on the inside, I wanna see it change the RSC mechanism into a full scale XUL type interface mechanism, where it doesn't need a desktop of it's own. Each Atari program pops up as a window on your favorite desktop, wether that is Unix, Mac OS or Windows.
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Re: The BAD DMA Chip myth

Post by oehansen »

joska wrote:The "myth" has it that only early STE's had this problem. They had TOS 1.06 fitted, so if your STE was originally fitted with 1.62 I think you should be safe.

http://members.optusnet.com.au/~colbee1/DMAFAULT.HTM

Code: Select all

C025913 - 38 PH23 - 001A
That is the one in my ST that I am doing all this on. :-)
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marcello
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Re: The BAD DMA Chip myth

Post by marcello »

joska wrote:The "myth" has it that only early STE's had this problem. They had TOS 1.06 fitted, so if your STE was originally fitted with 1.62 I think you should be safe.
I just discovered today I had this f* chip after random file corruptions on two different Atari branded hard drives (using TOS and Minix)
I have a french 520 STE with tos 1.62 so it looks that the distribution of this faulty DMA chip has maybe nothing to do with the TOS revision number.
STMint, try Unix on your 68000 Atari http://subsole.org/st_mint
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Re: The BAD DMA Chip myth

Post by oehansen »

marcello wrote:
joska wrote:The "myth" has it that only early STE's had this problem. They had TOS 1.06 fitted, so if your STE was originally fitted with 1.62 I think you should be safe.
I just discovered today I had this f* chip after random file corruptions on two different Atari branded hard drives (using TOS and Minix)
I have a french 520 STE with tos 1.62 so it looks that the distribution of this faulty DMA chip has maybe nothing to do with the TOS revision number.
Has nothing to do with the TOS version ... my personal belief is, that there is a monostable gone bad inside the chip. And as ST's age, it can basically happen to any ST, even with the good DMA chips. However these "good" chips have a higher quality parts, which makes it more resistant. Or, that is my understanding.

As I said earlier, it gives me a 30+ ns window ... which is way off the 160+/180+ ns window that Atari stated.

And not to mention, that many of the devices try to increase throughput speed, even beyond what Atari specs say. Pushing the limits, while in reality a much safer bet would be to rely on 30+ ns one, and to stretch the cycle between the byte bursts.
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dlfrsilver
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Re: The BAD DMA Chip myth

Post by dlfrsilver »

any news about this problem ?

oehansen, do you plan to create something to patch in a durable manner the buggy chips ?

both my STF and STE have the dreaded bad chips :( and i can't find replacement chips :(
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Re: The BAD DMA Chip myth

Post by qq1975b »

rocket-dog wrote:I have a Mega with a duff DMA. Neither my US or Syquest drive works. And nor does my external 3.5 drive which I believe is controlled by the same chip. The onboard floppy works just fine.
I have a Mega 1 with the same problem...It doesn't show any desktop icon or garbage name folders and files... The internal FDD works fine. I connected a Megafile 44 with ICD controller and ICD Pro drivers.

I have to see which DMA chip has...
Trying to learn...
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Re: The BAD DMA Chip myth

Post by qq1975b »

Do the "IMP C100110-001" DMA chip and the "C025913-38 PH23-030 5G1 65 " work ok with HDD on an Atari Mega 4?

Or is it better to use the C025913-38 or even better the good STe DMA chip?
Trying to learn...
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Re: The BAD DMA Chip myth

Post by exxos »

While this thread is a little old now, I still see it being referred to , so my thread below should be classed as a continuation to the "bad DMA" chip.

http://www.atari-forum.com/viewtopic.php?f=15&t=28504
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