"It is hard to draw any concrete conclusions from this amount of limited experience but one thing is glaringly obvious. All Bartons are not created equal. Some simply are not up to running at 200MHz FSB even when every other component on your mainboard is up to the task. Looks as if the luck of the draw has a lot to do with it.

Also, we tried underclocking the CPUs as well while still running an overclocked FSB, but this made no difference in the stability of the 2500+s or the 3000+.

Now the next question that you might be thinking is what do I really loose if I am "stuck" at 166MHz FSB. We thought we would look at this as a worst-case scenario as we have not seen any chips that would not do at least 185MHz FSB stable."

More here.
Update by Per: You might be interested in taking a look at this site and their findings regarding the product code all AMD CPU's has... Disappointingly though [H] did not include the product codes of the CPU's they tested.

Try this link to get the full lowdown on finding an overclockable AthlonXP. They explain how to overclock an Athlon XP 1700 to perform like an Athlon XP 2800, or even 3100. There is even a link to an online store that sells the models that are overclockable.

Athlon XP 1700 JIUHB - An Overclocker's Wet Dream

You can buy one here for only £45.94 ...

CPU City

I read that the other day. Per Hansson said he was going to email Kyle and ask which cores they were.

Hey you guy just read the links I posted and all your problems are solved (200 fsb stable/oc cpu cores and where to buy).