I don't have an EWS, but for the Maestro 32/96 you can find Maestro.asm in my 4th post in this topic.
It isn't much in terms of firmware though, just a PnP info table.

Thank you very much!

Could you please tell the exact command parameters (for resource.exe) to upload the asm to the card? Do I first need to convert this asm file to another format (ini) ?
Or I simply launch resource.exe and fiddle with the menu items...?

Currently I don't have any way to test the procedure on vintage hardware.
But from memory:
-Start resource.exe
-Read eeprom data from file -> type 'Maestro.asm'
-Write eeprom data to card
Done. 😀

Worked!
The codec can initialize by cs4232c.exe, cs4232cfg.exe. Not with Terratec.exe, though. (give strange memory area errors). I will figure out the correct lines for config.sys or autoexec.bat and test the card.

I hope someone can dump some info from an EWS64XL rev 1.2, too. Rev 1.0 might be OK as well. For a start, that is.

You need to Override the PnP settings for Maestro. That dump and Override helped me get the thing to work.
I used to have an EWS64 XL, maybe you can ask the person I sold it to.

Is he a forum member here or any major retro sites where I can reach him?

You can find him on Amibay, his nickname is Puny. He bought it recently so he might not have installed it yet. Hopefully he will help you 😀

Thanks! I am checking in right now 😀

I forgot I cannot yet send PMs over there. Sent you a PM instead, Stojke...

^ make a couple of posts, it will unlock PMs

I just want to report that I managed to revive both the Maestro and EWS64 XL, thanks to forum members gerwin, stojke and elianda.

The solution for the Maestro was a single EEPROM reprogramming and re-init. (with overriding PnP configuration as suggested, forcing all settings from file instead)

The EWS64 took at least 4 EEPROM reprogrammings (I don't have the slightest idea why) and it had to be isolated as a single sound card in a bare system with only a video card as company. But in the end, it could successfully initialize codec, synth, MPU401... with native utilities (ewsmixer, ewsinit, ewscfg)

The only issue that remains is quite a mystery - the card is not enumerated at POST anymore as an EWS64 XL but as a simple "PnP card". It is sort of cosmetic, and I might be able to amend it as elianda has already dumped the EEPROM/ROM contents from a working EWS64 XL for me (big thanks!)

That is good news!

The post screen identification: I think is just states the name in the PnP info table. I quote from these files:
MAESTRO.ASM = 'TerraTec Maestro 32/96'
CSMODDED.ASM = 'CS4232 Sound Card'
PCA70PS.ASM = 'Philips PCA70PS'

Can you share the EWS64 specific file(s) here please?

OK, here they are.
But these are in a different file type, the dump was not done by resource.exe so I am still thinking about how to convert it to .asm

Thanks. 😀
The .asm files I gathered, were created by the resource utility, after reading the information from the soundcard.