To test the new AMD Athlon 64 X2 3800+, we used an NVIDIA nForce 4 SLI based motherboard from Asus, the A8N-SLI Deluxe, that had been upgraded to the latest BIOS available (v1013-002).
The rest of the components used in our test bed consisted of a Corsair TWINX1024-3200XLPRO 1GB memory kit, capable of 2-2-2-5 timings, a Radeon X800 XL, a 10K RPM Western Digital "Raptor" hard drive, and the oversized Thermaltake cooler you see here.
Before we begun benchmarking the Athlon 64 X2 3800+, we fired up the latest version of CPU-Z to get some detailed information about our specific processor. If you take a look at the screenshots above, you'll see that the Athlon 64 X2 3800+ is clocked at a default speed of 2.0GHz (per core), with support for MMX, 3DNow!, SSE, SSE2, SSE3, and x86-64 instructions. One thing of notable importance on the processor info tab was that the "Processor Selection" drop-down menu was selectable. On single-core processors, this is not the case.
CPU-Z's cache information page didn't reveal any unexpected information, other than the fact that it reported the information for only one of the Athlon 64 X2 3800+ processor's cores. The second core has exactly the same specifications, but the total amount of on-die cache is not reported as a single "grand total" that's twice as large as a similar single-core processor.
We also tried to overclock the new Athlon 64 X2 3800+, and had some interesting results. We began by raising the VCore voltage to 1.425v, and lowering the multiplier of the HyperTransport link to 3X, from the default 5X. We then raised the memory's supply voltage to 2.9v, and configured the memory to run at 333MHz instead of 400MHz. We then raised the motherboard's base HT frequency until our test system was no longer stable. In the end, we were able to hit a final, completely stable clock speed of 2.5GHz (10x250MHz). An increase of 500MHz, or 25%. We were actually able to hit much higher frequencies, but couldn't keep our test system stable. At about 2.6GHz, we could get Windows XP to boot to the desktop, but running applications caused instability. And at 2.7GHz, Windows would begin to load, but would blue-screen before reaching the desktop. Perhaps with more exotic cooling, beyond the traditional heatsink and fan we use here, the Athlon 64 X2 3800+ will overclock even higher than this.
We should also report that our Athlon 64 X2 3800+ ran relatively cool throughout our testing, regardless of whether or not the CPU was overclocked. While running at its stock clock speed of 2.0GHz, the CPU idled at about 33oC, and while under load we never saw its temperature surpass 39oC. And while overclocked to 2.5GHz, our sample CPU's idle and load temperatures hovered between 41oC and 48oC.