Similar to an earlier post I'd created, I'm now experiencing issues with AGP cards when the Windows 98SE system has more than 512MB RAM, or when having to invoke `MaxPhysPage` and `MaxFileCache`.

My Win98/Win2000 dual-boot system has 3x 1GB RAM sticks, and in order to boot Windows 98SE successfully, I have the following in my SYSTEM.INI:

1[386Enh]
2MaxPhysPage=20000
3
4[vcache]
5MaxFileCache=524288

The system works perfectly when a PCI VGA card is installed. However, when I install an AGP card, the system is never able to increase the desktop resolution and colour beyond 640x480x16 colours - Safe Mode style. If I try to do so, the system always wants to restart (not apply settings on-the-fly) and never manages to return to Windows. I've tried multiple versions of drivers and have eventually narrowed this issue down to the physical amount of RAM installed in the machine.
Once I remove the 3x1GB sticks and replace these with 1x 256MB stick, the desktop resolutions are able to be configured correctly.

I suspect the `MaxFileCache` restriction prevents further (or sufficient) memory being allocated to the AGP card, as it may be being used by the cache?
I've tried playing with various BIOS settings (AGP fast writes, read/write state delays, PCI/VGA pallette snooping, initial display boot being either PCI or AGP etc...) however, none of these have made any difference.

It's quite inconvenient to keep physically replacing RAM in order to boot Windows 98.

What doesn't help is that I'm using a 3Dlabs Oxygen VX1 32MB AGP4x card, which are notorious for bad driver quality. That said, when using the 256MB RAM stick, there are no further issues with the card.
Unfortunately, I don't have another AGP card at hand to test and compare the results and was wondering if this may be a general AGP/Windows98 issue when using large amounts of RAM.