For early gens it would have been DDR200 or 266 depending, I'm assuming DDR200 (advertising was a bit iffy then as DDR was totally new) which would have been old school stuff 100X2, I'm guessing that's what you had?
I couldn't get my Duron to run for love or money outside of DDR 200 but it made such a huge difference it was unreal.
That said, I was also on a bit of a campaign at the time. I spent a little time after high school in a tech college for PC tech and there was a bunch spending a lot on the likes of high end Athlons/early XP chips etc. I spent some Christmas money to buy and then mod the aforementioned K75SA bios to unlock multipliers for oc'ing and grabbed a Duron. The K75SA motherboard was pretty much the cheapest supporting motherboard stocked by most local shops at the time and online wasn't great. Ended up with a heavily OC'd Duron + DDR at 200 + a Geforce Ti4400 (luckiest time in my life apparently as I ordered a ti4200 and got a free upgrade).
It absolutely crapped all over the wealthy students prebuilds on the same course.
As an aside, RAM speeds were a big issue with computing around the time I got into it. My first ever personal (not family member) PC was around the Pentium 3 and Athlon Thunderbird eras, marketing for P3 was peak. The Athlon Thunderbird was actually on par or faster a lot of the time vs the Pentium 3 in real world performance. All of the advertising and many review sites didn't give a like for like comparison, they listed P3's with RAMBUS/RDRAM rather than standard SDRAM and it cost a damned fortune to the point of being untenable for 99% of people. There's a reason it swiftly died out, but between that and iffy software compliers it put AMD on the back foot for yonks outside of the enthusiast market.