It'll be a little faster for using the 945 over the 865, you'll lose Windows 98 compatibility but gain access to PCI-E graphics cards; it will still have severely lower single threaded CPU performance than a Core2 on an 865 and have no compatibility advantages over the even faster sandy bridge platform in Windows XP.

It'll be a little faster for using the 945 over the 865, you'll lose Windows 98 compatibility

ICH6 and 7 are still compatible with Windows 98 unofficially. Although Intel LAN (chipset integrated) won't work and USB 2.0 ports will work in USB 1.1 mode.

Drivers are here: http://windows98.xf.cz

P.S.
I doubt i945 will have any significant perfomance benefits over good i865PE or i875P board.

You can abuse 4GB of RAM :

PCI-e GPUs :

AND if you sources :

Even NVMe SSDs (second PCI-e slot required, if you need PCI-e GPU) B)

agent_x007 wrote:

You can abuse 4GB of RAM : […]
Show full quote

You can abuse 4GB of RAM :

cachemem.png

cachemem0.png

PCI-e GPUs :

Fire Strike Ultra.png

AND if you sources :

Fire Strike Ultra OC2c mini.png

Even NVMe SSDs (second PCI-e slot required, if you need PCI-e GPU) B)

Thank you all. I was thinking to rebuild a main config using a "fastest" single core cpu and the two choices would be or the socket 478 3.4 Prescott I have or the socket 775 661 3.6 depending on which mobo I'll buy.