X-bit labs

AMD Sempron 3100+ Overclocking (page 4)

Category: CPU

by Ilya Gavrichenkov

[ 10/10/2004 | 09:39 AM ]

Overclocking AMD Sempron 3100+

We’d like to put down our goals first. We don’t want to set any overclocking records – our aim is simply to check out the performance of the Sempron 3100+ in real-life conditions – just as you may want to use it in your own system. So we didn’t use any special cooling methods and didn’t modify anything in the mainboards. We just took an ordinary processor sample, a standard cooler and an off-the-shelf mainboard and did our overclocking with simple and easy methods – by changing the BIOS Setup parameters.

First of all we decided to watch the Sempron 3100+ overclock on a rather old, but still popular ABIT KV8-MAX3 mainboard. Against our own recommendations explained above, this mainboard is based on the VIA K8T800 chipset.

This mainboard is widely recognized by PC enthusiasts; it allows increasing the frequency of the clock generator in a rather wide range and also controlling the voltage of the CPU (Vcore can be increased above the nominal by 1 to 350 millivolts), memory slots (from 2.5 to 3.2v), AGP slot (1.5-1.65v) and HyperTransport bus (1.2-1.4v).

Thus, our first testbed was configured like that:

• Mainboard: ABIT KV8-MAX3;
• Cooler: Thermaltake Silent Boost K8 (A1838);
• Memory: 1024MB DDR500 SDRAM (Corsair CMX512-4000PRO, 2x512MB);
• Graphics card: ASUS RADEON 9800XT;
• Hard disk drive: Western Digital WD400JB.

Our testing started out smoothly enough. Without fine-tuning the system or raising the core voltage, we reached 229MHz of the clock generator frequency. Thus, we easily made our Sempron 3100+ speed up from its normal 1.8GHz clock rate to 2.06GHz! The system was absolutely stable at that.

But a further increase of the FSB clock rate – even by a single megahertz – led to the system becoming non-operational. The computer would just hang up at a launch of any 3D application. We tried to persuade with it by raising Vcore and reducing the frequency of the DDR SDRAM modules, but to no effect. It means that our graphics card became unstable at a higher AGP bus frequency, and we didn’t really hit the frequency limit of the Sempron 3100+. Due to the synchronous architecture of the VIA K8T800 chipset, the AGP frequency grew from 66.6MHz to 76.3MHz when the clock generator frequency was set to 229MHz. The graphics card we used definitely didn’t like that.

We had already met such troubles with VIA’s chipsets before. You should also know that the most fastidious part of synchronous chipsets from VIA at overclocking is not the AGP bus even, but the SerialATA controller integrated into the South Bridge. This controller is clocked synchronously with the V-Link bus, which in its turn is clocked relative to the PCI frequency in the K8T800 (and in other VIA’s chipsets, too). Keeping this fact in mind, we refused to use a Serial-ATA hard disk drive in our testbed; otherwise, our experiments would have ended up much sooner – at about 220MHz frequency of the clock generator.