Falcon Stability Issues

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DominoTree
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Falcon Stability Issues

Post by DominoTree »

Before I dig in too far, was wondering if anybody has any thoughts about likely culprits. My Falcon030 is great and stable when I fire it up, but after it's been on for a while it becomes more and more unstable. Mostly throwing bus errors, but sometimes it's all sorts of everything.

I have the Exxos clock patch board installed and I'm using my Exxos PSU, and the 14MB Exxos memory module, and just recapped the entire system. Recapping seems to have helped a bit but it falls over after use, much more quickly using my FreeMiNT environment.

Running the latest EmuTOS right now but it doesn't seem to be related to the ROMs I put in the system.

At first it seemed related to IDE access, but I think that was more related to a bad device I was using - SCSI-only behaves the same way.

I have logic analyzers and oscilloscopes and a full complement of test gear at my disposal if there's a specific thing I should be looking at.

Any thoughts?
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stephen_usher
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Re: Falcon Stability Issues

Post by stephen_usher »

The problem you have here is that it’s not a hard fault. i.e. you can’t say that after it gets warm it stops working totally. This means that you can’t use something such as a freeze spray as things working correctly again could just be random chance.

With a “warming up” issue I would start with the simplest option of reflowing solder joints, just in case.

Does it fail similarly if the Exxos memory board isn’t in there?

How’s the fan?

How hot is the CPU getting?
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exxos
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Re: Falcon Stability Issues

Post by exxos »

If you have a recent clock patch, did you do the resistor mod ?
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Steve
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Re: Falcon Stability Issues

Post by Steve »

Reminds me of @mikro's issue: https://exxosforum.co.uk/forum/viewtopic ... 69&p=83562

His turned out to be a wandering piece of solder on the board, I think he put the board in the dishwasher and it fixed it.

Then after washing it he also found:
So... even if this were true, what now? In a pretty hopeless mood I took my (only) magnifying glass, to check on the Combel (it was really just a box checked in my head, no expectations whatsoever)... looking at it, looking... and then I see a small blob of solder on one of its tiny legs! Actually in two places! Well, to make the unnecessarily long story short ;), using the classic soldering iron, the glass and a razor I somehow managed to get rid of it and not destroy the Combel.
But yes what Exxos said too, make sure you've done the resistor mod on the clock patch too.

For good photos of how to install the 100k resistor mod: https://www.exxosforum.co.uk/forum/viewt ... =18&t=4885 and another angle: https://www.exxosforum.co.uk/forum/viewt ... =18&t=4813
DominoTree
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Re: Falcon Stability Issues

Post by DominoTree »

Thanks for the suggestions!

Hadn't done the 100k resistor yet but it's been on the list to try - I'll give it a go and see what it does.

The board itself is pretty clean but I'll go over everything a bit more closely and make sure the solder joints on the memory connectors and whatnot are all good as well.

Nothing seems to get overly hot in the system, and it behaves the same way with the OEM 4MB module as well. I also set the wait states back to default with no effect. Also tried without an FPU as well as a couple different ones and that didn't seem to do anything either.

If it still behaves the same way after the resistor and I don't find anything else that seems off, I'll see if I can't find a more reliable way to trigger the issue than "I've been using it for a while" and start taking some readings and hooking up probes.
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Re: Falcon Stability Issues

Post by mikro »

From my experience, as you could see above, I would recommend first to observe the system:

- does it crash when left as is, even with not moving the mouse?
- does it crash on boot? (at least sometimes)
- does it crash when something is happening? (moving the cursor, opening a window, loading a file, ...)

This is what helped me during my hunt, the crash sounds very generic but it usually has specific reasons and symptoms which help to track the problem down.
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Badwolf
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Re: Falcon Stability Issues

Post by Badwolf »

Also, if you have EmuTOS in, it gives realy quite good feedback on exceptions.

You say it's mostly bus errors, for example. I'd start compiling a list of where the errors are occuring. See if there's anything common going on. Just take a pic of the crash screen each time and collate them later at your leisure.

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DominoTree
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Re: Falcon Stability Issues

Post by DominoTree »

Badwolf wrote: Tue Jun 07, 2022 12:57 pm Also, if you have EmuTOS in, it gives realy quite good feedback on exceptions.

You say it's mostly bus errors, for example. I'd start compiling a list of where the errors are occuring. See if there's anything common going on. Just take a pic of the crash screen each time and collate them later at your leisure.

BW
So I finally got back to this and the bus errors were only being thrown with the exact same instructions accessing the FPU or writing to $8604 (FDC DMA) which (I believe) use the same clock. I installed the 100k resistor as suggested and kept seeing the same two instructions triggering a bus error (but funny enough I was never able to capture ~BERR going low)

~DTACK signals didn't look terrible, and I started doing some further digging.

I started playing with DMA2DSP.PRG, and after about 10 minutes from a cold boot, it'd start throwing a few errors and would continue to increase until there were LOTS of errors. After looking at some of the original errata, I saw that Atari suggested changing R221 to 0ohm from 33ohm (and I believe they updated the schematics between revision G and H)

I did notice that if I touched the clock patch board while there were errors happening DMA2DSP.PRG, they would disappear and it would stabilize (although I didn't wait ~10m to see if it would destabilize again)

As a long shot, I bridged both R221 pads together with the Exxos clock patch installed, and I ran DMA2DSP.PRG for several hours followed by several hours of GEMBench on loop and it's absolutely rock-solid now, at 0 ROM wait state, with the 3-cycle delay disabled on the clock patch.

I've checked impedance everywhere that seemed to make sense and I've got good grounds and whatnot, so I'm not really sure what the issue might be, but I've got a stable system now, so I'm gonna call it good and catch up on some other projects that've been on hold now that everything seems solid.

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exxos
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Re: Falcon Stability Issues

Post by exxos »

Would be useful if you posted images of your install.

I am working on a v4 clock patch for more problematic falcons. But not sure when it will be ready. Prototypes are done and part tested. Just time is always the limiting factor.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
DominoTree
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Re: Falcon Stability Issues

Post by DominoTree »

This is all I happen to have right now but I can take better ones - anything outside of the modified things worth looking at? Also attached what ~DTACK looks like (the first rabbit-hole I went down) FWIW.

When I bridged both R221 pads with a solder blob (still connected with the bodge wire) it became absolutely rock-solid and I still haven't seen any issues after some heavy use.

After this photo I switched the solder blob to disable the 3-cycle delay.

Glad to take pictures or measure anything that might be helpful.

Also FWIW I think the board was straight from the factory with no mods or patches ever done, if that's helpful.

(current desktop for posterity lol)

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