kolderman wrote on 2021-10-26, 21:39:
There are no Win98 drivers for any Core2Duo platform. It may well be unstable.
not true, 865-chipset s.775 mobos with c2d support and win9x drivers are a thing, the asrock 775i65g being one of the more popular ones of those. These do work really well for both 98 and XP. Of course you're right that they're not ideal for DOS, though. But, instead of building a DOS/Win98 PC and a separate XP PC, why not build a Win98/XP PC and a separate DOS PC... or, hell, why not build a Win98/XP PC and just use emulation for DOS, after all there isn't much that real DOS hardware can bring that emulators can't
As said earlier, the Asrock 775i65g r2.0 pairs great with a C2D E4700, or alternatively if you would like a low tdp single core cpu, you can go for a Celeron 450, which is basically a tualatin p3 on steroids.
For PSU, just use any good quality modern PSU that you'd like, no need to use a retro PSU with a system like this. You will not need much power, a 300-450 watt psu is more than enough. So get any new, good quality brand-name PSU you wish. That CM should do fine.
2 gigs of ram is a good idea as well, XP could certainly use that. 98 by default has trouble with more than 512mb, but you could either use a rloew patch to fix that, or alternatively use some method like himemx to limit the available ram to under 512mb under win98, and have the whole 2 gigs available on XP only.
For case, if you like that Silverstone SG11, you can use it, no reason not to, will do fine.
GPU: here things are a bit more complicated. Nvidia FX 5900 will have splendid game compatibility for 98, but performance for XP will be rather poor. Nvidia 7800 GS AGP or 6600/6800 series AGP card would be very fast for win98 and decent for XP, but the game compatibility for 98 is not perfect. Also these cards suffer from "bumpgate" (meaning that sooner or later they will die, they're not exactly long-term reliable). Probably best to go for ATi instead, like a Radeon 9800 could do quite nicely here. Same as Nvidia 6800/7800GS it won't have ideal game compatibility on 98, but at least it's quite a bit more reliable, and has nice image quality to boot. A Radeon X800/X850 can work too, the 98 drivers are beta but they seem to do the job just fine, and those cards will net you much needed performance for XP games to run nicely.
Sound card - definitely the Audigy 2 ZS. And make sure it's a retail card, should have "SB0350" in the serial number on the back. If it has like "SB0358" or "SB0359" - pass.
Finally, HDD, anything you like really, as previously said. IDE, SATA, SSD, HDD, it will all work. Win98 unpatched will work with up to 64gb if you try to format it trough the win98 setup, or up to 128gb if you format it in advance from a newer OS. WIth bhdd31.zip patch you can go beyond 128gb and up to 2tb even, so don't shy away from large HDDs if you have any handy
Finally, optical drive, you do need, a lot of win98 games with redbook audio (music that plays from the CD while you play the game), and because you will want to use .vxd audio drivers for win98, you won't be able to virtualize it with daemon tools or similar software, so a real optical drive is a must. And it has to be IDE, no SATA, because you will need to run a cable from the optical drive to the sound card and only the IDE drives have the connector. CD or DVD up to personal preferense, as is the brand as well, just make sure it works fine, a lot of the older optical drives have various deffects and issues by now, its surprisingly tricky to find one in perfect working condition up for sale.