Thus, our theoretical reasoning above is confirmed in practice. To overclock the Sempron 3100+ well, you need a modern mainboard capable of clocking the AGP and PCI buses asynchronously, i.e. a mainboard on the NVIDIA nForce3 250 chipset. So, the second part of our testing was continued on an EPoX EP-8KDA3+ mainboard.
The EPoX EP-8KDA3+, like the ABIT KV8-MAX3, offers widest opportunities to the overclocker: you can change the clock generator frequency from 200 to 400MHz, clock the AGP bus independently at 66 to 100MHz (with a symmetrical change of the PCI bus frequency), control the CPU multiplier (reduce it below the nominal), control the voltages (increase Vcore to 1.8v, Vmem to 2.8v, Vagp to 1.8v, Vchipset to 1.75v; the nominal voltage of the nForce3 250 chipset is 1.6v). Thus, the EPoX EP-8KDA3+ is an excellent overclocking tool (running a little ahead, we should say it did well throughout our tests with the Sempron 3100+, too).
So, we continued investigating the overclocking potential of the Sempron 3100+ on the following testbed:
- Mainboard: EPoX EP-8KDA3+;
- Cooler: Thermaltake Silent Boost K8 (A1838);
- Memory: 1024MB DDR500 SDRAM (Corsair CMX512-4000PRO, 2 x 512MB);
- Graphics card: ASUS RADEON 9800XT;
- Hard disk drive: Western Digital WD400JB.
Overclocking the Sempron 3100+ went more cheerfully on this testbed. Setting the clock generator frequency to 230MHz for a start, we enjoyed an absolute stability of our system. Clearly, the nForce3 250 chipset allows avoiding those overclocking impediments the K8T800 imposes on Socket 754 systems.
Thanks to that, we easily reached 250MHz clock rate of the clock generator – just adjusting the appropriate item in the mainboard’s BIOS Setup. The processor frequency became 2.25GHz and the CPU itself remained perfectly stable. We should note, though, that the EPoX EP-8KDA3+ mainboard thinks that the regular voltage of the Sempron 3100+ is 1.5v rather than 1.4v as it should be. So, the processor voltage was initially higher than normal.
To continue our overclocking further we had to adjust some of the system settings. The memory frequency was growing along with that of the clock generator (1:9 divisor in the BIOS Setup), and it reached DDR500 at 250MHz of the clock gen. That was the guaranteed maximum of the PC4000 modules we used in the test system. We changed the divisor to 1:11, so that our overclocking wouldn’t be limited by the capabilities of the memory chips.
Steadily lifting the clockgen frequency up we reached 270MHz, and the CPU clock rate became 2.43GHz. However surprising it may seem, the Sempron 3100+ was absolutely stable at that, even without our increasing its voltage over 1.5v. Thus, quite effortlessly, we sped the Sempron 3100+ up from 1.8GHz to the frequency the top-end K8 processors are clocked at. I mean the Athlon 64 3700+ and 3800+ and the yet-unannounced 4000+.