Other issues have popped up - investigating. ADI signs on as SiS SI 7012 on ECS7610ultra board. Difficult to get 'Mute' to stay off and chosen %vol to stay selected between boots. New problem, loaded devx and lost video! Lots more to look at, probably reload and start again.Was that sound chip recognised by any other pups? That is, out-of-the-box without needing an extra driver to be installed?
As for sound on other Pups, X-Slacko-Slim 4.4r10 sound works on a lot of these old boards now, didn't in previous versions, but that is primarily a 32bit offering which has been tested on 32bit machines, so need to run it on some 64bit machines as well. Also need to check BIOS settings as the old stuff often needs new battery and BIOS reset.
Later:
The default sound settings allows mute/unmute and settings levels to be set - no sound. Run ALSA utility - no supported cards?
Run on P4 system with same onboard SI7012 - sound working.
Hmmm. Looks like an HW fault then. That's not entirely unknown on elderly kit. Will try to install discrete PCI sound card tomorrow....