to be specific deba ang AMD Athlon 64 3000 (S939) stock Speed is 1800MHz

so I'm guessing nothing is wrong with your core. as what they've mentioned the model number doesn't equate to clock speed in AMD
venice core = moderate to high overclocking possibilities
and according to some OC gurus I've read somewhere last year (I forgot what forums):
sample results from a Winchester core
stable OC: 267 x 9 = 2400 MHz (from the looks of it murag lisod iabot ug 3.0Ghz w/o sacrificing stability)
stock Speed: 1800 MHz
OC'ed by: 600 MHz