Thanks for the suggestions.
Yes - all the latest drivers installed. Benchmarking is a bit tricky - I didn't do it for the old mobo...and now I can't. It may only be subjective but the HDD is waaaay slower now! But I wondered whether anyone might have a view on the absolute numbers.
I've checked the Device Manager and all channels are DMA of some flavour.
It's a shame because the rest of the kit is fairly high end and worked well straight out of the box with the ASUS board. Sadly I needed a working machine when the old board died so I went for a quick solution - but I kind of assumed that I'd get similar performance from a reasonably well known brand.
I'm fairly computer savvy but tweaking hardware and the like is not something I've got much experience of so I'm a bit lost on this one and haven't really had time to research.
Ho hum....