Most any Nf2 board out there lock the AGP/PCI bus and sometimes offer an option to overclock the AGP bus independently.

The reason you can't get a 13X is because even though most boards unlock it for you they don't allow the higher multiplier mapping to be enabled or in the case of higher muliplier cpu's like the 2400+ whcih uses a 15, you can go down to 13, but not below. The multiplier mapping (hi or lo)depends on what model you have. 12.5< is low. 13> is high.

Only a few boards allow multiplier unlocks across the board. Tis why I bought Abit NF7's, since they allow that. Asus doesn't offer that feature and I was quite surprised when I found they didn't enable it. I forget what other company had it.

Also the SiS746 chipset autolocks the AGP/PCI bus. On my ECS L7S7A2 it's like this. In order for me to have a higher fsb/lower multiplier, I use the wire trick in the socket to enable the lower multi maps, since that bypasses the cpu bridges. Quite easy to do and I don't have to mess with connecting the bridges on the cpu which I like.