Thought I'd cap this one off. I'm using a Supermicro P6DGE dual P3 using the i440GX chipset and 1.5GB installed memory. System performance seems to suffer if 2GB is installed; I suspect this is because the addressing limit of the chipset is maxed out and the BIOS makes some unfortunate choices as a result. AAR, not a Win98SE issue and 1.5GB is fine.
My final solution for Win98SE involved several steps.
The first was to edit SYSTEM.INI and
change the MaxPhysPage and MaxFileCache values.
Then, apply the
Unofficial Win98SE SP2.
Next, since a potload of memory was going to go unused, I installed the
HIMEMX.EXE XMS driver and the
XMSDSK.EXE RAMDisk driver. Note that if you're going to use Windows 98SE, you need to include the
/t (load at top of XMS area) switch, otherwise Windows gets confused.
The last hurdle for me was using an ASUS TNT+ VANTA AGP card. Windows refused to accept that it was there, insisting on using the generic 16-color 640x480 VGA driver instead. That was fixed by going to desktop-properties->settings->advanced->adapter and telling Windows to use the AGP drivers that already had been loaded. You get a warning message, which it's safe to ignore.
The RAMDisk is being used for browser cache and system temp files. I don't think it's a good idea to try to use if for swap file, as XMSDSK is a real-mode driver and switching modes might not result in the performance improvement that might be expected.
I'm up and running. Operation seems to be pretty smooth.