With socket A there's locked and locked. Earlier they had a set multi that was downward unlocked, but you could still set higher multi on the bridges, later they got locked so even the bridges did nothing, but maybe the mobile bridges still worked and it was able to be used at various mobile multi, and then there was locked locked locked where neither motherboard, bridges or mobile multi settings worked. ... but also crossing the 12.5 multi from either direction has issues, as it requires another bit set that motherboards may not have implemented, or might be a less well documented jumper, i.e. it's not obvious it's for higher multis. So that when you try to set below that multi, it's wrong because you're setting it to 18x or something because the other bit is still held, or when below and try to set high it goes down to 6x or something.

RaiderOfLostVoodoo wrote on 2021-11-16, 17:49:

I did some research on overclocking Athlon XP and found out, that AMD started locking the multiplier at some point. Multiple sou […]
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I did some research on overclocking Athlon XP and found out, that AMD started locking the multiplier at some point. Multiple sources stated that AMD started locking the multi in week 35 of 2003, but still sold CPUs with an open multi at this point. Starting with week 43, all CPUs had their multi locked.

So I got myself a sample from week 30, to be sure it has an open multi:
AQUCA 0330WPMW
To my surprise I can't change the multi. I did lower the multi to 12 and it doesn't post.

Anyone got an explanation for that?
Might my CPU be a fake?

I've had a few socket A boards and all of them started without issues when I tried to set multiplier on locked CPU.
That's why I think that there might an issue with your motherboard BIOS. I would try few another multipliers - lower and higher than default one. If this won't change anything, then try another BIOS (newer or older one).

And if this won't help... you can always do mobile-mod and use software like WCPUID to change multiplier. It should be possible in range (IIRC) 3 - 24x for desktop CPUs.

I guess you updated the BIOS to the latest version 5.7!? There's also a beta BIOS, version 5.81. These BIOS versions apply to MSI K7T266 Pro2-A / KT3 Ultra / KT3 Ultra-ARU / KT3 Ultra2 / KT3 Ultra2-BR / KT3 Ultra2-R and are available on my website -> https://soggi.org/motherboards/msi.htm.

kind regards
soggi

The Athlon XP 3000+ is Barton core and I think all the Bartons for desktop PCs were with a locked multiplier. Some Thoroughbreds had been unlocked. I'm not sure about Palomino, I can't remember if I had it unlocked.

The Athlon XP 3000+ is Barton core and I think all the Bartons for desktop PCs were with a locked multiplier.

Nope. Also Barton and Thoroughbred-B CPUs were both manufactured almost alongside each other and until the end, latter as Sempron and Geode series.

To my surprise I can't change the multi. I did lower the multi to 12 and it doesn't post.

Certain multiplier may lead to problems.

With socket A there's locked and locked. Earlier they had a set multi that was downward unlocked

Not really, high-end Thunderbirds (1333/1400) were just unlocked from the get go. There was simply no benefit for locking multiplier, since they've already being pushed to the limit and practically no motherboard supported multiplier higher than 13x in BIOS.

The Serpent Rider wrote on 2021-11-17, 14:18:

The Athlon XP 3000+ is Barton core and I think all the Bartons for desktop PCs were with a locked multiplier.

Nope. Also Barton and Thoroughbred-B CPUs were both manufactured almost alongside each other and until the end, latter as Sempron and Geode series.

I don't dispute that, but were there any Bartons with an unlocked multiplier? A good source of info was on fab51.com, but unfortunately I can't get there anymore.

I use XP-M - mobile cpus. It's the same socket so you can use it in a normal desktop motherboard. Usually they use 133MHz FSB and you can go to 200Mhz and change the multi as you need it to.

I don't dispute that, but were there any Bartons with an unlocked multiplier?

Most of CPUs AMD made in 2003 were fully unlocked.