I just upgrade my old abit bx6 with a 900 celeron and a coppermine slotket.
From what I understand, it doesn't matter if the multiplier is supported by the motherboard
or not because it is just ignored. For example, this board's highest multiplier is 8 but it
works fine with this celeron. So, any processor of the same type should be ok as long
as it gets the right voltage. BTW, I used a startech slotket from buy.com for $10.
The newest celeron is about 1.3 GHZ @1.5 volt. But, the 900 is a much better deal.
I got mine(retail version) for $50. So far, it has made 1.01GHZ- 9 * 112 -and is cool.
However, the next bus speed I have is 133. As for slotkets, they must be for fcpga or coppermine
to work correctly. I hope this helps. good luck