Edman wrote:

a beta BIOS F2g (removing some hw limitations)

Seems to me there might be a good reason it's a "beta BIOS".

Sounds like you've tried all the obvious settings. The only other thing I can suggest is to try using HIMEMX in your config.sys, mostly because it's easy to try. Otherwise, maybe you'll have to switch to a non-beta BIOS and live with the hardware limitations.

@ Jorpho: Thank you. I'm not that skilled, but HIMEMX is not going to fix the Linux issue, right? It does not use config.sys, that's DOS based, correct? I'm afraid that reverting BIOS will cause the CPU to not be recognized. The official support is 550MHz only. I guess it will be safer to find another board or just toss the SFF case idea - shame.

Edman wrote:

I'm not that skilled, but HIMEMX is not going to fix the Linux issue, right? It does not use config.sys, that's DOS based, correct?

Indeed. I don't know what you would do about the Linux issue.

Did you find out what is conflicting?

You can try running the attached utility with both configurations (FX 5XXX & Quadro) and compare the outputs for differences. The utility is supposed to work under Win9X systems. If the utility runs successfully, click on the 'OK' button(bottom left) and then click on 'Save All'. It may contain some personal information(in case you think of uploading the output).

Which lubuntu version are you using? You can check the /var/log for various logs that may possibly contain verbose error messages to point you in the right direction.

@ gandhig: Thank you. The Lubuntu is 17.04. The installation menu (to my knowledge) does not put any logs anywhere. HDD is untouched and instllation runs from a CD. With the FX card, it won't even start to install. Thank you also for the utility, I'll check it just to try and learn what was happening. In the meanwhile, I've sort of solved my problem by getting an ASUS A9250. It's a dirt cheap 128MB DVI low profile card and also works flawlessly like the QUADRO. So - for the moment I don't need to hunt that bug down for the immediate effect. Should I find out anythig interesting about the FX line, I'll post my findings. Thank you again.

Sorry, it was my mistake to wrongly think that you got Lubuntu installed, but had problems with installing the video driver for FX5XXX.

Understood that you got a different graphics card which is working with your setup.

Still, if you are interested in troubleshooting FX 5XXX in Lubuntu, you can try the install by adding 'nomodeset' to the menu entry. You may be aware to remove the 'quiet' and 'splash' options for a verbose boot mode.