KT133 and early KT133A are officially incompatible with any Athlon XP. But unofficially you can use anything, including Barton core. There's one major caveat though - it's literally a lottery. One CPU may work and other won't, even if they have identical core and rating. So you can arm yourself with a bunch of Athlon XP CPUs and experiment.

CPU compatibility is probably mostly limited by avaliable multiplier options. Earlier S462 often only go up to 12.5x.

If CPU have locked multiplier - it doesn't matter.

The Serpent Rider wrote on 2022-02-02, 11:20:

If CPU have locked multiplier - it doesn't matter.

Exactly, same with CPUs with multiplier <13 and completely unlocked CPUs (those will run at what speed the board sets them at assuming they can run that fast).
Partially locked multipliers are tricky, that's where compatibility is often flaky.

Multipliers have nothing to do with it.

If you say so.🤷‍♂️

The Serpent Rider wrote on 2022-02-02, 11:18:

KT133 and early KT133A are officially incompatible with any Athlon XP. But unofficially you can use anything, including Barton core. There's one major caveat though - it's literally a lottery. One CPU may work and other won't, even if they have identical core and rating. So you can arm yourself with a bunch of Athlon XP CPUs and experiment.

Thanks. I was thinking to some XP Mobile, maybe even the Geode cpu I've almost never used with some manual setting even if they need a 133Mhz FSB let's see if they can work @ 100Mhz. It'd be interesting for the SSE but also the PowerNow! feature helpful in idle times on the PSU. These configs seems mostly having a fixed stressing power demand while even the P-III Katmai on the 440BX seems had some power saving feature internally at least from some test I did lately with much variable power values at the plug.

afair 12.5 multiplier wasnt the problem since there was a mod to add another strap so you have all the options all the way to 24x100
At least thats what I did to my A7V133 to run Duron 1800 at 15x133MHz after unlocking it http://fab51.com/cpu/barton/athlon-e24.html

back in the day you could read about it here
http://www.a7vtroubleshooting.com/forum/cgi-bin/yabb/YaBB.pl still available at https://web.archive.org/web/20070308012812/ht … ?board=tweaking
dead http://www.ocforums.com/showthread.php?s=c8f5 … threadid=279392

There was bios mod by Braziliantech? implementing "HLT on Idle" among other things.

I would rather try Athlon XP with Palomino core first (if you have one). Some early revisions of KT266(A) boards won't even boot with "standard" (non-mobile) Thoroughbreds.

ASUS A7V 1.02 is probably not the best board to try and get an Athlon XP working on.
I used to work with quite a lot of A7V and A7V133 boards (with lots of varying board revisions) and in the end it was really just a crapshoot and not only because of the CPU but also memory compatibility could be really flaky. These boards really wanted very particular settings and particular memory modules in a particular order and these boards loved good quality stable PSUs (with good 5v of course) and good airflow.

There used to be an awesome forum at I think http://www.a7vtroubleshooting.com/info/cpu/index.htm but it's long gone now.
There's still some of it archived here https://web.archive.org/web/20071016054244/ht … in/yabb/YaBB.pl but a lot of the stuff seemed to be missing when I last tried browsing that archived forum.
Still imo it was the most invaluable source of info regarding these ASUS boards and I ended up loving them! (but I still kinda hated them 🤣 but these were always a nice challenge).

Your board, I'd say your best option would be to find an Athlon Thunderbird 1400B. Underclocking a 1400C will get you only to 1050MHz and using the pencil trick to unlock would iirc get you 1250MHz or so at best (and the procedure could be flaky).

Iirc it wasn't just the FSB or the BIOS that was lacking, the Athlon XPs needed extra filtering or something which these older boards didn't provide. Some board would work with some Athlon XPs and some combinations would not work.
I barely tried getting faster CPUs to run with A7V but with A7V133 1.05. (with a dot) I did get a Palomino 2000+ running with either 512MB or 1024MB SDRAM, can't remember exactly.

Have fun! 😜
But don't expect too much from it 😜

Thanks for these answers. 😉

I remembered right on the ram memory problem, in fact I had in the past one of these boards I think to remember they were a bit patience demanding. Also a lot of components and capacitors and I think I didn't try many cpu or at least I don't remember any more than the usual last Athlon were working in that. I still remember anyway the ram problem even the slot might have worked only with the right ram module combinations and not as a single module.. something like that.
Anyway I immediately updated the bios to the 1011 cause I don't know what changed on the beta latest 1012 final version but already up the 1011 version reading release notes felt quite important updates. Now running the original Athlon 1000 I might try the Duron 1300 (SSE) as first update, then the Athlon 1400, than the other XP, Mobile, Geode options.. 😁

I was running a Tbred A 1700+ on mine "in the day" didn't seem much point going past 1.5Ghz due to diminishing returns, being held back by SDRAM. Having said that, it didn't seem much different in use than DDR systems with around that speed of CPU in. Mind you I wasn't trying any high end for the time gaming on that one, I only gave it an MX400 for pixel pushing.

Interesting, I have an untested (unfortunately) AX1700DMT3C that I might try on it.

I was probably on the latest beta though.

I will probably update it too but I don't even know what's changed it seems like only few months later update but it might support something more. Meanwhile the 1011 bios seems theorically have solved few problems indeed at least on paper.

For now I'm testing its stability with the Athlon 1000 it came with and it seems it's stable. I always check those many capacitors cause I'd expect them to be already quite stressed considering ICs on the board are around middle 2000 dated. I was reading now that the Geode cpu should have the complete features set of the 3DNow!, SSE, PowerNow!, it'd be nice to configure that.

If I use the Jumperfree mode for the vcore, an unsupported cpu like an XP or even the Geode, would the mainboard still read and set at least the required voltage core or it would boot in some "random" voltage? Cause I might set it manually but the lower still would be 1,1v compared to the 1,0v of the cpu, I suppose it'd not do much difference but just to know it would not boot with some 1,8v burning the cpu. 😉
Also interesting in the manual the FSB jumpers even for the 1.02 rev is said to go up to 133Mhz/33 so I might also set the correct FSB. I was expecting it from the next chipset version not this.

AMD had more sense when planning their VID signals than intel, the whole range was in the spec from the start.

one thing you might consider is it possible to have thermal runaway with some of these chips (I pretty sure i cooked my original Tbird 1.2 Ghz when i had the cpu fan off. Thankfully it was cheap to replace)
i think this was resolved with the XP series.

Pickle wrote on 2022-02-02, 20:23:

one thing you might consider is it possible to have thermal runaway with some of these chips (I pretty sure i cooked my original Tbird 1.2 Ghz when i had the cpu fan off. Thankfully it was cheap to replace)
i think this was resolved with the XP series.

If with thermal runaway you mean frying because of overheating, I fried one of these chips by forgetting to add TIM to the otherwise properly installed HSF and the CPU fried within seconds (didn't even make it to the POST screen, it stayed black and the CPU was dead almost instantly).
Iirc the CPU I fried was a Palomino though. This was on one of the A7v133 boards which may have something to do with this but the thermal protection was still wonky from my perspective, much less reliable than for instance contemporary Pentium 4 thermal protection.
AMD added something resembling a real thermal protection only when they released Athlon 64 I think. Anyway I wouldn't take the risk with Athlon XP.