for over 10 years, I was using 32-bit WinXP on "Asrock h87 pro4" motherboard with i7-4770, when finally, few months ago, the Asrock motherboard died from an old age (over 10 years it was working everyday at least 8 hours per day). now the same CPU lives again in another motherboard, but this time Fujitsu brand with Q87-chipset and again running WinXP.

so, as far as 8-series chipset are concerned, there are WinXP drivers for everything , including the build-in HD4600 GPU in the CPU, in fact it's quite decent GPU - I am not sure, but maybe it's faster than anything that was available during WinXP era.

IMHO, there is no any advantage to go after 9-series chipset, because the only difference is M.2 support plus potentially some real incompatibility problems with XP and/or missing drivers - at least I've never used WinXP with 9-series chipset to speak from experience.

I must say that even 8-series chipset are the 1st in which Native PCI support was removed and those motherboards use external PCIe-to-PCI bridge chip compatibility with old PCI cards is very good, the only not-working-cards, I found, are PCI VGA cards that are using 8415A I/O addresses (but those are not common - most PCI VGA cards work), as those are not translated by those bridge chips. so, if you want 100% perfect PCI compatibility the latest you can use is i7-3770 and 7-series chipsets, i.e. Ivy Bridge.