I do not think it will support above 8x multiplier unless you can do some type of mod. Looking at manual page 3-4 it appears it could support thru 8x but hard to tell.

Looking at the same diagram I'd wager it'd go up to the same 8.5x limit as my SE440BX-2, unless maybe closing multiple jumpers does anything special. I suppose I'll just have to do some good old-fashioned Testing™️ once I get everything in... the multiplier is of lesser concern to be honest, as on a 100MHz bus I imagine there's not much difference between 850MHz and 1GHz. I'm more concerned at the idea of Coppermine CPUs working at all. Plus, my slotket might be of some limited help in getting the multiplier problem sorted... I'm not honestly sure yet.

Epox recommend (at least for the rev 0.5) up to 600 / 600E but there are plenty of BX boards capable of 800MHz - 1GHz so it'd be worth trying.

Yeah, see, it's the Rev 0.5 bit that has me concerned -- mine is a 0.4. I just hope I'm not restricted to PIIs -- that'd really suck. It also makes the distinction that it's with a 2Mbit BIOS chip -- I hope it's already magically got one, but I'm growing more doubtful by the moment. It'd probably be too much work to get ahold of a compatible chip and flash it since I don't have access to an EEPROM programmer. Plus, the table has me thinking someone would have to go patching in support if that's even possible for anything above that.

If I can't get higher-end coppermines to work on here, would anyone happen to know any models of 440BX board that would outside of the really popular (read: expensive) ones?

Well, turns out it's not as hard as I thought -- here I am using BP to hack up an already hacked-up (to add 128GB disk support) BIOS for this board!
Now, that said, I'm only going to use this image with a flash utility as a last resort. I don't want to go bricking a board on a whim. But, if this does work... it'll be so cool!

I've the OEM version of the SE440BX-2 (the -3) from a Dell and it happily runs the 1GHz/256/100 coppermine on a variety of slockets and it has a Yamaha sound chip on-board. There are a few good BX boards but for what they are, they can be pricey. It looks as if most of the microcode updates from Epox were for the 2Mb bios images (1999-2000) rather than the 1Mb ones (1998), but hopefully you'll get lucky with your bios hack 😀

I'm hoping I get lucky and just slot something in and it works, the BIOS hack is only for if nothing else works because I get the feeling there's a good chance that I'll brick the board with this.

My SE440BX-2 was a Dell OEM as well! Like I said, it came from an XPS T600r, and even with the latest BIOS I could find, it'd turn its nose up at anything with a multiplier over 8.5. I wonder if I should dig it out and give it a shot again with the MS-6905v2, since last time I was just using some no-name slotket that may or may not have been intended for Celerons only.