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.
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.
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?
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.
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.
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.
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...
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
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.
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