My question is, how much RAM are you using in the system, @precaud? 512MB? 1GB?
My intention was to use 1GB but some tests showed it wasn't needed.
Yeah, no, 512MB is the golden amount. You will probably never use that much under 98, and going above that causes stability problems. If you do want your system to have more memory, though, say, for the XP installation, check out HiMemX. It limits the amount the RAM 98 sees, all with one executable and a line in config.sys. I have no issues in my P4 machine with 2GB of RAM installed, which dual-boots 98 and XP.
Now, here's my experience. I own an Asus P3B-F, a slightly newer version of the P2B-F I presume. I had a while ago bought an Intel Pentium III 1.1GHz 100MHz FSB S370 SL5QW (a hard-find online) as well as a MSI MS-6905 Master as per recommended here. I wanted to see, even though the board doesn't officially support it, if I could run the CPU with a slocket, given it has an FSB-speed 100MHz, the same as the board. So, I threw them together, slotted the slocket-CPU combo into my P3B-F, hit the power button, and... nothin'. No POST. So I let the matter rest.
In a very hopeful attempt to fix my non-working PS/2 mouse port on the board (it basically renders all keyboards, PS/2 or USB, non-functional, if you enter the BIOS or Windows with a PS/2 mouse plugged in), I decided to recap almost the entire board with brand-new Nichicon polymer caps. 🤣 While it didn't really solve the PS/2 problem, it did however allow me to POST with that slocket combo for the first time. The BIOS detected it well enough, and I was able to get into Windows 98 okay. However, I noticed that I would receive memory errors (?) with certain programs under 98, and when I tried using different AGP GPUs with the slocket combo, I also noticed some GPUs would not initialize properly and I would get no video out on the board.
The take-away is this. While you might be able to run a non-supported fast 100MHz FSB P3 on that board (maybe with a recap with modern capacitors), who knows what issues you'll then run into under Windows and such. If you want a fast Slot 1 motherboard, then get an Asus P3V4X, which I'm happy to say runs my P3 1GHz 133MHz FSB S1 SL4BS just fine. 🤣 If you don't want to get a newer Slot 1 motherboard with better CPU support, then you're kinda stuck to whatever the motherboard officially supports, or at least nothing too far beyond what it does.