Benefit in which application?

Celeron Mendocino is almost as fast, clock-for-clock as Deschutes/Katmai P2/P3, so yes, upgrading to 533MHz would give you a nice boost. The high multiplier (and so relatively slower memory access) will prevent it from actually reaching 533/333 of the speed, but 1.25x or so faster in CPU benchmarks is entirely possible.

That said, what chipset does this XPS have? If it has a ZX or BX, you could consider getting a Celeron 333 and running it at 100MHz FSB, 500MHz CPU. As that would also boost RAM up to 100MHz, that would certainly outperform 566MHz CPU at 66MHz FSB.

But will any of this let you do something you can't already do? Not so sure. You'd be better off getting a 1999/2000 era system for that and leaving the early 1998 XPS in period correct state IMHO.

Chipset is a 440LX so 66MHz is as high as FSB will go.

appiah4 wrote:

Chipset is a 440LX so 66MHz is as high as FSB will go.

Then - assuming no Coppermine BIOS and voltage support - C533 is as high as this system will go. Still not entirely sure it's worth the effort to turn a flagship high-end early 1998 system into a low-end 2000 system...

Back in the day, my friend had the same XPS D but with a PII 300 which was later upgraded to a Celeron 466 using a slotket. That's a lower 55.3% increase in clock speed compared to your 60% increase, with real-world performance subject to the limits of 66MHz FSB. It was a noticeable boost for general use and gaming (he also upgraded the original Rage Pro 8MB AGP to a Savage 4 32MB AGP); you'll have to decide whether the theoretical maximum improvement of 60% is worthwhile.
The BIOS needs to be flashed the original Intel AL440LX BIOS for Celeron support, I remember using the BIOS recovery option with a floppy. If you're not already aware, this page covers the options https://www.roberthancock.com/dell/xpsdproc.htm.