If you're fishing for a C1 chip, and get a B0 chip, don't automatically dismiss it...give it a shot.
The last four 1.8 B0 chips I've tried would hit 3GHz on the stock Intel heatsink...others have had good luck too.
This last chip I received is REALLY nice.
It's a 2.0A, packdate 11/27/02, SL68R, MALAY.
I was going to just skip it because it was B0...but I'll be damned if this sucker isn't running 20x154 3080MHz right now.
At DEFAULT voltage...1.45v actual. With the stock Intel heatsink.
It's in an 8IHXP with 1GB PC1066 154x4 right now...it'll actually hit Windows at 156x4 (board's limit) with default voltage, but the RAM craps out at 154x4 (which is actually quite impressive for four 256MB Samsung PC1066 sticks).
I'll be chunking this in a less limiting board and a Vapo very soon...it's a helluva chip. $165 for a 1GHz+ overclock at default voltage stock cooling is impressive.
So try 'em...I've had a 2.5, 2.66, and several 2.4B C1 chips that would NOT hit 3GHz, no matter how much voltage I fed 'em. C1's are just as hit-and-miss as B0's, apparently...and it appears that the B0 process is having some very good yields as of late.