With original setup no.

1. You can make C: partition 500MB and than the rest as extended partition D:

2. or use DDO software to use larger partition:
http://members.shaw.ca/rinocanada/hdutils.htm

3. if your 486 uses PCI than you can use some EIDE PCI card like Promise TX.

I can vouch for the BIOS extender. I use it on my 486 laptop which also has the 504MB limit.

I use Maxtor MaxBlast DDO and it works fine with a 16GB SD card. Sadly, the disk controller is so old that it only goes up to about 2MB/s; I tried a real disk and an ssd with the same result. So I settled on an class 10 SD card which is more than enough.

Access times are great though.

Does MaxBlast let you move the media between other PCs? I tried using Ontrack to get my P100 to see beyond 8.4GB but it creates a special "Ontrack" partition that can't be accessed by other computers without some trickery.

I have used the XTIDE BIOS (in a network card boot ROM) to get around the obsolete CHS translation used by my 486 BIOS, which prevented me from moving the SD card back to a normal PC (as the sectors were written out of order.) I believe this will also avoid the 504MB limit.

I use WD EZ-Drive and yes, you can put the CF into another computer and copy files onto it 😀