Here's an article in relation to your overclocking endeavors of the Athlon 64 3800+:
"Since the AMD processor, Athlon 64 X2 3800+, appears the slowest model in the dual-core processor product line from AMD, it will be of our primary interest in terms of its overclocking potential. To test the overclocking abilities of this processor we assembled the same testbed as we have just used for performance benchmarks, i.e. based on DFI NF4 Ultra-D mainboard. For CPU cooling we used a Thermaltake CL-P0200 air cooler.
The default processor clock frequency multiplier of our Athlon 64 X2 3800+ equals 10x, so the only thing you can do with it is to make it lower (due to Cool'n'Quiet support).
As a result the CPU can only be overclocked by increasing the clock generator frequency. In order to avoid being limited by the potential of the other system components, we locked the PCI and PCI Express bus frequencies at their nominal values for the entire test session, and the multiplier for Hyper-Transport bus was reduced to 4x.
The memory frequency was also set with a reduced divider value, which would guarantee that the DIMM modules would work for sure even when the clock generator frequency grows up.
During our tests we found the maximum clock generator frequency when the processor remained stable. It was 240MHz. To go beyond this limit we had to slightly increase the processor Vcore: we raised it to 1.45V. The resulting CPU frequency in this case made 2.4GHz.
So, during our overclocking experiments we managed to raise the frequency of our Athlon 64 X2 3800+ on Manchester core by 20%. I have to stress that it is not that much at all, as dual-core Athlon 64 X2 4800+ and Athlon 64 X2 4600+ processors work at exactly the same frequency. And the latter is based exactly on the same Manchester core. In other words, we managed to overclock our Athlon 64 X2 3800+ only to the level of Athlon 64 X2 4600+.
Looks like AMD doesn't use the best cores for the youngest processors in its dual-core family. For example, when we tested Athlon 64 X2 4800+ processor, though this one was based on Toledo core, we managed to conquer the 2.7GHz bar.
In order to give you a better idea of how fast the overclocked Athlon 64 X2 3800+ actually is compared with the top AMD processors, we ran a few specific tests. We compared our today's main hero against the Athlon 64 FX-57 and Athlon 64 X2 4800+. For a more illustrative result we set the memory at 200MHz in all benchmarks and adjusted its timings to 2-2-2-10.
The Athlon 64 X2 3800+ overclocked to 2.4GHz wasn't number one in all the benchmarks, but still gave impressive results. Although we have to admit that it nevertheless demonstrates very nice performance.
For example, in applications supporting multi-threading it manages to outpace Athlon 64 FX-57. As for its lag behind the Athlon 64 X2 4800+ equipped with 1MB L2 cache for each of the cores, it is not that big at all: only 1-2% on the average.
However, there were a few applications that turned out very critical to the cache-memory size. In applications of this time the performance difference between the overclocked Athlon 64 X2 3800+ and the Athlon 64 X2 4800+ can reach up to 10%. Although this can hardly upset the happy Athlon 64 X2 3800+ owners, as their solution costs half as much as Athlon 64 X2 4800+ and Athlon 64 FX-57."
That's pretty much all you can do and I learned a lot just form reading it so if it helps me, I'm sure it will open your eyes to OCing your 3800+.
