What is the AmigaOne XE DMA fix?

Whenever I have a hardware compatibility problem with, for example, PCI cards

I'll almost always get asked if my AmigaOne has the DMA fix installed.


I'm fairly recent to the Amiga Scene, so I do not know what this fix does.




So, what does it do?

Where can I find this on the motherboard?

How can I install/uninstall it?

Is there a software "check" program to determine if this fix is installed?

Does any XE owner with 2GB ram working has this installed?

Do you recommend me to perform this fix?



Almost all info about this fix seems to have vanished from the internet
so I hope anyone here can inform me.

@Helloworld

Lets see, i had this DMA (and audio chip) fix installed back when i still had my XE.

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There was a problem with the original run of XE motherboards which could lead to a crash or freeze when using e.g. internet through the onboard LAN chip.
iirc it was a missing resistor, but this might be my memory failing me

It was a "hardware" fix, meaning, someone with the knowledge soldered an extra cable to circumvent that (at least i had a cable there)

Other people might be more detailed in the works of the fix

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If you turn around the motherboard and look at the backside, you "could" see an extra cable soldered, that *could* mean you have the fix installed

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You can't uninstall it unless you remove the fix, it's hardware based and once you got it, it should remove some of the hardware/software problems you might encounter

Personally i was happy to have it, because it made my internet work without killing the system everytime

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Not really, see above for the cable (but that's maybe not the sole solution to install the fix)

If you have no problems, don't change anything

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I personally was never able to *work* with more than 1 GB in my XE.
The onboard southbridge is just too flaky and picky about memory modules.

You might be able to install 2 GB of RAM and even survive the boot process into WB, but you will probably crash hard once a program access RAM beyond the 1 GB border.

Stick with 512 or 1 GB, you'll be fine

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I'm not sure, some people are surely still doing this fix, but as i said above, if nothings broken, don't fix it.

Any hardware tinkering can kill your board for good

@Helloworld

PM me if you would like the official Eyetech PDF file.

@Raziel

Excellent! thank you


@lemen

Please do, PM sent

They could use this PDF on intuitionbase

@Helloworld

Fix USB&DMA for AmigaOneXE_G4 and ArticiaS:

https://amigaone.files.wordpress.com/2 ... onexe-dma-usb-fix-1z2.jpg

https://amigaone.files.wordpress.com/2 ... onexe-dma-usb-fix-2z2.jpg

@Raziel

Quote:

All XEs and SEs had the same conflict with the LAN when the ATA controller had DMA enabled. Only the Micro A1 had shipped with the fix. A few people knew how to perform the fix at the time, while Alan Redhouse refused to make the fix public and somewhat prophetically warning that there may be unforeseen consequences. It was later discovered you had to disable USB when using a RadeonHD card if your board had the fix done.

Most people either disabled the ATA DMA or installed a PCI ATA controller to get around the problem.

@Helloworld

The DMA fix is best avoided but there was a separate USB fix which resolved the problem with USB devices not being recognized after being unplugged and another being plugged. It's better not to make modifications to a working XE and if you have any niggles with your USB you can resolve them with an active USB that has it's own PSU.

P.S.

I hope that Hans can get that 7750 of yours working.

@Lemen

Great to hear that those documents still exists !

I have the AmigaOne G3-SE.
When I got it it had two blue cables soldered on the back-side, however I would love to know the details of this and to check if it's the full fix applied.

Would it be possible to send me a copy also ?

Besides from what looks like the fix applied, I have the Sii0680 card, a new NEC USB 2.0 card and a Forte sound card installed. However, the machine is very picky, if I remove the USB card then it affects the IDE card and will not allow UDMA 6 mode suddenly. I have 2 GB registered ECC ram installed with no issues.

Thanks a lot !


@Rob

Thats also very interesting information!
My system seems to have both fixes applied on the back side. However, it still has issues that happens with it. I have disabled the onboard a1 IDE as using UDMA 6 with it would lead to corruptions, and also the onboard USB ports. I am able to use UDMA 6 with the attached Sii0680 IDE and Sii3114 IDE boards if my NEC USB card also is installed in a PCI slot, currently the middle one (..!).
Onboard ethernet seems stable as long as the NEC USB is not used. If I have even a keyboard plugged into the USB NEC card it can suddenly crash the machine when the onboard ethernet is used.. or just by itself. So, I don't use the USB, either onboard or the NEC card.

I'm curious how the machine would act if I removed the fixes and depended on the PCI IDE and USB cards like I do now.. Maybe it would actually be stable, as long as I left the onboard IDE and USB disabled and alone, both in U-BOOT and disable the loading of the drivers in Kicklayout.

By disabling DMA, you mean setting the transfer mode to PIO in U-BOOT as opposed to one of the UDMA options ?
Is there some trick I could do to make the NEC card stable when used ?

Thanks for the information!

EDIT: I got hold of the Eyetech docs, and also looked at the backside of my board. The only fix that seems to be installed is two wires going from the ArticiaS to the 3com Ethernet chip. Maybe they routed it to two exclusive PCI signaling pins. Not sure of the details, yet.
My board definitely still has the DMA issue, apparent when using USB.
Maybe I should apply the fix from ArticiaS northbridge to the VIA southbridge.

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I could be wrong, but that's not the way I remember it. I don't remember any effect on USB, but the "fix" made it impossible to use a graphics card in any of the three PCI slots (only the AGP slot was usable).

On the other hand, it was fifteen years ago...

I'm also pretty sure that the "fix" only applied to the XE, not to the SE.

I had a fair amount of stability issues in my non-fixed A1XE G4, especially with USB. Even with a USB PCI card, I found that USB transfers would often crash or fail.

Then I replaced the CPU cooler and everything became alot more stable. USB failures became very rare.

@monomango

PM sent

There seem to have been a couple of separate issues from what I have read so far. It involves the VIA and ArticiaS chip.

Firstly, the VIA chip is screwing up the onboard DMA, as it is not initialized correctly according to some sources. However, if that was true it should have been solved by a u-boot firmware update long ago..
Regardless, the Eyetech doc contains a workaround that should stop the VIA chip from putting out the garbage data that leads to freezes under certain circumstance - importantly when using the onboard 3com Ethernet.

Secondly, there was a bug in the ArticiaS related to cache coherency and DMA usage. This was already solved by AmigaOS by using software cache (at a possible performance impact). The Pegasos board, which used the same chip ArticiaS Northbridge but a different Southbridge (not VIA), later got April and April 2 fixes implemented as logic next to the ArticiaS. This can be seen in The Pegasos Book.

My SE board only has one fix applied. On the backside two wires goes from ArticiaS and to the 3com chip location. This could be to solve a separate SE issue related to the onboard Ethernet, which I have no info about, or to fix another ArticiaS issue. So no DMA fix is implemented.
Therefor, the use of the onboard 3com Ethernet is also crippled by the onboard DMA issue which can freeze the system or bring down a transfer over Ethernet. It might only be happening when a hard drive is set up to use a UDMA transfer mode, regardless of using onboard or PCI board IDE such as Sii0680 or Sii3114. However, I suspect it’s even independent of that, i.e. just because Ethernet uses onboard DMA.
Using the onboard IDE in UDMA mode can in addition corrupt data written to the drive, so I never use onboard IDE. PCI based IDE will not corrupt data written in UDMA mode, however the onboard Ethernet could still be affected by it leading to the freeze issue, or the connection falling out.

I have observed the following to avoid all the issues.
Using an Ethernet PCI card, like the RTL8169 gigabit Ethernet, makes the whole system stable, non of those freezes I could previously have when using onboard Ethernet. Then of course, PCI IDE card can also be used freely in all UDMA modes. No issues.
So, for me, using PCI based IDE eliminates disk corruption upon write in fastest UDMA mode, UDMA 6. Similarly, using PCI based Ethernet eliminates the instability that could lead to random freezes.
I never plug anything into the USB, as that can possibly trigger the DMA issue and possible freeze. Commenting out EHCI in Kicklayout could make it fine, possibly. Not tested enough, probably true when using a USB 2.0 card. Using my NEC USB PCI card seems to also be affected by the onboard DMA issue. Usage of USB must be researched more.
Interestingly, my system can only use the UDMA modes of my PCI IDE cards (sii0680 and sii3114) if either my NEC USB 2.0 card is connected or the onboard USB is activated in U-Boot. If no USB is active, it will fail to boot in UDMA mode. This indicates that somehow USB presence is strongly linked with the onboard DMA issue.

To sum it up, here is the current configuration, it gives me a stable system with no freezes or Ethernet dropouts :

———————————————
ATI Radeon 9200 AGP graphics

PCI cards installed (top to bottom):
Forte Media FM801 sound card
RTL8169 gigabit ethernet (3com onboard ethernet gave freezes/dropouts)
Sii0680 IDE in UDMA 6 mode (any mode is fine, Sii3114 can also be used)

Onboard USB ports 1 and 2 enabled in U-boot. Never used.
U-boot is version 1.1.4, and I run the G3 CPU stable at 667MHz, core voltage of 1.64V, up from 600Mhz at 1.59V. This gives about 10% higher FPS in Quake 3, confirming that the Quake 3 frame-rate is indeed CPU-bound in the system.
———————————————

If I could use one more PCI slot I would connect the NEC USB 2.0 card. However, I would rather have UDMA 6 IDE transfers from the Sii cards than some extra USB ports that possibly triggers a freeze by the DMA issue.
I don’t know the details, maybe it’s possible to get a USB card that handles its own DMA rather than being controlled by the buggy onboard one, the usage of PCI IDE and Ethernet cards increases stability and avoids the freezes, a PCI USB card should ideally do the same.


Finally, some links of relevance :

https://amigaworld.net//modules/newbb/ ... =40&viewmode=flat&order=0

http://forum.hyperion-entertainment.com/viewtopic.php?f=16&t=1889

https://amigaworld.net//modules/featur ... at_id=3&rev_id=41&sort_by



@Lemen
Well appreciated. Thanks a lot!

@tonyw
The SE has the same VIA and ArticiaS chip.. so I’m sure it could be applied there too, if the correct pins are found (pcb layout a bit different).

@Raziel
With AmigaOS 4.1 FE above 2GB of memory can be used. This change might even have come with 4.1.

@Helloworld
I run with 2GB, no issues.
Gotta use Registered memory, I use Registered server grade SUN ECC modules @133MHz.

Do you have the DMA fix applied?
How does the system behave after? No issues and stable?