Yes you can use both. It's only a physical space limitation

there's nothing preventing you from doing it apart from space constraints by the component (and connector) sides facing each other, they're sharing the same slot position after all.

ElBrunzy wrote on 2020-10-02, 15:23:

I'm in the impression that the chipset support both and it's only a limit design specification. With modern SMD design and the growth of 3/4 isa/pci socket 7 motherboard offer on ebay, we can imagine a demand to use both. Anyone where successful at it and have example case scenario ?

I have successful experience with an old good Slot-1 (440BX) mainboard, installing ISA sound card + PCI raid/USB combo controller in such slots. To connect them both, I have used cheap like dirt PCI riser from China (like this one), and mounted the combo atop of other extention cards at right angle (there's enough room in my case for that). USB is wired to the front panel, so direct access to the bracket of PCI card is not needed.

The only issue was low quality of the riser, I had to resolder couple of contacts on one of the connectors to make it working, but since then I'm using this setup about a year and have no reasons to complain.

oh, interesting, a ribbon riser why did I not think about that...

I was wondering if any combo where made to take advantage of both isa and pci slot. Like a daughterboard that would fit on the isa slot too. I guess it would make for a very niche project and the marketing department advised against it. I'm not sure if the ISA bus can bring any advantage to the PCI bus anyway.

ElBrunzy wrote on 2020-10-04, 00:39:

I was wondering if any combo where made to take advantage of both isa and pci slot. Like a daughterboard that would fit on the isa slot too. I guess it would make for a very niche project and the marketing department advised against it. I'm not sure if the ISA bus can bring any advantage to the PCI bus anyway.

Of course, ISA can bring advantage!
And there indeed were PCI cards coupled with ISA cards, see eg. Tekram DC-690C(D) PCI IDE controller coupled with ISA "paddle board" to properly support IRQ14/15, or some PCI multi-I/O card where the FDC required similar connection with an ISA slot.
See also Asus Media Bus - essentially PCI-and-ISA-in-one.