Why stop at a socket 478 low end pentium 4? You can go higher. i865 AGP LGA 775 boards support higher clocked Prescott and Cedar Mill cpus, dual core pentium D cpus (not that dual core would make any diference in w98) and some i865 lga775 boards even support Core CPUs (actually all of them do if you can update the CPU microcode on the board's bios). Or you can go for a socket 754 / 939 build. ULi chipsets have extremely stable win98 drivers (even tough they're a little slower then the VIA counterparts). I built one such overkill multi-purpose rig (see my signature) and it's currently my main retro-rig. Just finishing up Quake 2 MP1 in glorious 1024x768 Glide OpenGL. Here's a link to the build thread (lots of pictures and some benchmarks): Win98 Socket 939 Voodoo 2 SLi Build! (a.k.a. Glide Overkill)
In my view, a 2GHz P4 is overkill for older win95 games, and too slow for some newer games like Doom 3. You could build a Chimera sistem that runs both DOS, Win98 and WinXP (and if you fancy it Windows 7). It will also run modern browsers unlike the venerable P4 due to SSE3 support.
Possible overkill hybrid DOS-Win98-XP builds:
1. Prescott / Cedar Mill / Presler build
- fast Cedar Mill Pentium 4 (like a 631 or a Pentium D 940)
- LGA775 intel i865 motherboard with AGP and DDR1
- X850XT or 6800 Ultra AGP card - these are the latest cards with win98 drivers. X1600 and X1900 series are rumored to have win98 modded drivers, but I could not find any to download and experiment.
- 1GB of DDR1 (you could go with 2GB, but I can't seem to get win98 to work correctly even after modding System.ini)
- IDE HDD (for better Win98 compatibility)
- Optional Voodoo 2 SLi for Glide Support
2. Cedar Mill / Presler / Conroe build
- P4 631 / Pentium D 940 / Core 2 Duo E6600
- LGA VIA P4M900 with either PCI-E or AGP (OR BOTH like on some upgrade boards), DDR1 or DDR2 (or both)
- X850XTX or 6800 Ultra AGP or PCI-Express cards
- 1GB of DDR2 (you could go with 2GB, but I can't seem to get win98 to work correctly even after modding System.ini)
- IDE HDD (for better Win98 compatibility)
- Optional Voodoo 2 SLi for Glide Support
3. Clawhammer / Newcastle / Venice socket 754 build
- the fastest socket 754 Athlon64 you can find - fastest one I could dig up is a 512kb 2400MHz 3500+, but if you look hard enough you might stumble on a 1MB 2.4GHz 3700+
- VIA K8T800 / VIA K8M890 / ULi (ALi) 689 motherboard - all have great win98 support. VIA boards are faster, but ULi boards have excellent win98 driver support. Stay away from nforce 3 boards - win98 drivers are available but they're a mess, and most of the time only chipset drivers are available.
- X850XTX or 6800 Ultra AGP or PCI-Express cards
- 1GB of DDR1 (you could go with 2GB, but I can't seem to get win98 to work correctly even after modding System.ini)
- IDE HDD (for better Win98 compatibility)
- Optional Voodoo 2 SLi for Glide Support
4. Clawhammer / Venice / Toledo socket 939 build
- the fastest socket 939 Athlon64 you can find - I put a 2.4Ghz 3800+ venice single core in my overkill Glide build and it's pretty fast. Of course you coud go with a 939 athlon X2 (toledo) but those are harder to find, clocked lower and you won't be seeing any benefit in 99% of games. If you really want dual core, go for a pentium D. Those are clocked much higher so the performance penalty in single threaded apps should be lower.
- VIA K8T800 / VIA K8M890 / ULi (ALi) 689 motherboard - all have great win98 support. VIA boards are faster, but ULi boards have excellent win98 driver support. Again, stay away from nforce 3 boards - win98 drivers are available but they're a mess, and most of the time only chipset drivers are available.
- X850XTX or 6800 Ultra AGP or PCI-Express cards
- 1GB of DDR1 (you could go with 2GB, but I can't seem to get win98 to work correctly even after modding System.ini)
- IDE HDD (for better Win98 compatibility)
- Optional Voodoo 2 SLi for Glide Support
All configurations mentioned above will work great in win98. Via chipsets need a little more fiddling under win98 - see this thread for what drivers you shroud use for the best performance and stability: Win98 Socket 939 Voodoo 2 SLi Build! (a.k.a. Glide Overkill)
I personally tested an LGA775 i865 / E6600 (/w modded bios) / x800xt AGP, a socket 754 ULi 689 / A65 3500+ / 6800LE AGP and socket 939 A64 3800+ / K8T800 / 6800XT builds, and had no issues under windows 98.
The main advantage of using one of the four configurations listed above is that you can sometimes get the parts for free or close to nothing (setting aside the high end 3800+, opterons and video cards). You don't even have to get a high end video card - a lowly 128 bit 128mb 6200 will do just fine. So will an x600 - and you might be able to pick those up for free as well.