Don't get a Sempron, thats AMD's equivalent of a Celeron. The lack of 64-bit and an L2 cache really hurts performance. Everybody hates socket 754, but its really not that bad. If you don't plan on upgrading your CPU yet keeping your motherboard, there is no harm in getting 754. Get the Clawhammer core. It has 1MB L2 cache which will make it scream.
Btw, the l2 cache doesn't hurt performance that much with the sempron. And wow, no 64 bit support. Its 2005. Microsoft will release longhorn 2007. Thats 2 years to get a better computer/upgrade processor.
First, the SSE3 instructions make very little difference, showing almost no performance gain in benchmarks showing the Winchester vs. Venice cores.
Also, if the guy is asking for a core-type suggestion, do you really think overclocking is a good thing to recommend?
Lastly, there have been some Sempron 3100+'s taht have gotten to 2.7 GHz on air with DFI boards. However, not all 3100+'s are capable of that, most will never even sniff 2.5 GHz, much less 2.7. Also, who cares how high the CPU can hit on a DFI board? if he doesn't have a DFI board, then that means nothing. I doubt he's going to go out and purchase a new motherboard simply so he can overclock a sucky Sempron.
And wow, no 64 bit support. Its 2005. Microsoft will release longhorn 2007.
People aren't buying the AMD 64 CPU's for the 64-bit capabilities, they're buying them for their superior architecture in the 32-bit realm. As you can see here the Sempron 3100+ is utterly destroyed by AMD's 64-bit line, even getting beaten by the 64 2800+, the lowest of AMD's line.
In conclusion, if not obvious, I would HIGHLY discourage against getting a Sempron, and would recommend a 3200+ or 3400+ Newcastle core. The 3400+ Newcastle is about $100 more than a 3100+ Sempron, but beats it by 33 frames per second. Unless you're into extreme overclocking, DO NOT go with the Sempron.
i was thinking about getting a Athlon64bit 3200+ w/ an ECS mobo (its a combo for cheap) would that be good? im on aa REALLY tight budget so i cant get much. and i really dont care what the core is either. i just want something dependable that is 64bit and fast.