im giving this tip for those who have problems o/c'ing their semprons 2800+ on ASRock K8Upgrade-NF3. this way i can thank the guys that helped me out and gave me tips on how to o/c my sempron...

these are my specs

Sempron palermo 2800+ 1.6ghz o/c'ed to 2.3ghz stock vcore at 1.45 stock heatsink and fan
OPN number: SDA2800AIO3BX
ASRock K8Upgrade-NF3 bios version 1.7
1x Kingston 512 pc3200 running at 266mhz
40gb seagate ultra ata x1
inno3d geforce fx 5500
samsung dvd/rw combo
samsung cd-rom

these are the settings

ht clock: 290
htl speed 870
multiplier: x8
dram freq: 232
2.5t
3t
3t
10t
12t
(this in is auto mode in the bios setup)

BEFORE O/C'ING REMEMBER TO LOAD OPTIMAL SETTINGS THEN BOOT THEN AFTER THAT YOU CAN TRY THIS NOW:

to overclock this step by step:
choose cpu/agp async: cpu200/agp66 (default)
change the ht-nb speed to 600
increase the fsb by 10mhz increments i.e. from 200 make it 210 then reboot then make it 220 and so on and so forth...
the max stable freq you can get is 2.3ghz that is 290mhzx8
then lower your agp clock to 60
i got mine running very stable at 1.45 vcore and stock heatsink and fan with no problems
i ran prime95 10 hours and its showed that the system setup is stable enough to accomodate the o/c
for the temps i got 40-42 mobo and 45-48 cpu that is on default vcore and stock REMEMBER

i hope this would help
any questions and corrections just quote the part and i'll answer with how i manage to do my o/c