X-bit labs

AMD Sempron 2600+ for Socket 754: K8 Architecture Made More Affordable (page 8)

Category: CPU

by Ilya Gavrichenkov

[ 03/04/2005 | 12:03 PM ]

The BIOS of the DFI LANPARTY nF3 250Gb is overclocker-friendly and allows doing the following:

• Changing the frequency of the clock generator from 200 to 456MHz stepping 1MHz;
• Tweaking the parameters of the memory controller. The mainboard offers enough flexibility in setting up the timings and other options. The number of adjustable parameters isn’t smaller than the number of options of the A64Tweaker utility;
• Choosing the memory voltage from 2.5 to 3.1V stepping 0.1V;
• Reducing the CPU frequency multiplier. The minimal multiplier is 4x;
• Choosing the core voltage with two options. The Vid option can be set from 0.8V to 1.55V stepping 0.025V; the Vid Special option can increase the voltage additionally by 4, 10, 13, 23, 26, 33 and 36%. Thus, the maximum voltage the mainboard can send to the processor is 2.1 volts;
• Adjusting the frequency multiplier of the HyperTransport bus. Possible values: 1x, 1.5x, 2x, 2.5x, 3x, 4x, 5x;
• Lifting the chipset voltage from the default 1.6V to 1.9V stepping 0.1V;
• Clocking the AGP bus from 66 to 100MHz stepping 1MHz;
• Increasing the voltage on the AGP bus from the default 1.5V to 1.8V stepping 0.1V.

So, we’ve got more than enough overclocking options here. Moreover, this mainboard comes with an integrated MemTest86+ utility that can check out the stability of the memory subsystem without booting up the OS. The mainboard also offers enough flexibility in setting the speeds of the fans depending on the temperatures of the computer’s various subsystems.

So, the DFI LANPARTY UT nF3 250Gb looks a most appropriate platform for overclocking Socket 754 processors. We met some practical problems, though, which you should be aware of.

First, DFI quite insensibly saved on the chipset cooling. The low-profile aluminum heatsink installed on the nForce3 250Gb chip is working close to its limit, so you may want to replace it with something more serious before overclocking the CPU.

The second problem is that the Serial ATA ports numbered 1 and 2 are implemented through an additional PHY controller from Marvell. This controller is very capricious about high clock-gen frequencies, and Serial ATA drives attached to this controller’s ports stop to work even at a slightest overclocking. So, you should disable the first two Serial ATA ports when overclocking the DFI LANPARTY UT nF3 250Gb and use only ports 3 and 4 which are attached directly to the chipset.

The third drawback of the DFI LANPARTY UT nF3 250Gb is the strange sensitivity of the memory controller to which exactly DIMM slots the DDR SDRAM modules are plugged in. It’s better to load a pair of modules into the first and third DIMM slots at overclocking, but the use of a single memory module is the best choice. Our experiments suggest that it’s only in the latter case that you can overcome 300MHz clock-gen frequency.

Thus, the prerequisites for a serious overclocking of the Sempron 2600+ processor on the DFI LANPARTY UT nF3 250Gb mainboard are 1) put a better cooler on the chipset, 2) don’t use the first two Serial ATA channels, and 3) use a single memory stick. Keeping these points in mind we assembled the following system to overclock our Sempron 2600+:

• DFI LANPARTY UT nF3 250Gb mainboard (BIOS N32LD128.BIN);
• AVC Z7U7414001 cooler;
• 1GB Corsair CMX1024-4400C25 DDR550 SDRAM;
• PowerColor RADEON X800 XT graphics card (AGP 8x, 500MHz/500MHz);
• Western Digital Raptor WD740GD hard disk drive (Serial ATA-150).

Meeting the above-mentioned requirements, this testbed gave us no troubles as we were investigating the overclockability of the Sempron 2600+. The mainboard did its job well.

Without increasing the core voltage above the default 1.4V we managed to overclock the Sempron 2600+ to 2.28GHz. That is, the system remained stable till 285MHz clock-gen frequency. This looks already impressive, but we know that the overclockability of AMD’s 90nm cores is likely to increase at higher voltages.

The Semprons work at a lower voltage than the 1.5-volt Athlon 64. So we lifted the voltage of our Sempron 2600+ up to 1.5V and found that the processor remained stable until 302MHz clock-gen frequency. In other words, the Sempron 2600+ could work at 2.42GHz frequency at 1.5V voltage.

In order to get even higher we increased the core voltage to 1.65V. The processor reacted to that by remaining stable at 2.5GHz (313MHz clock-gen frequency). Frankly speaking, the system would start up even at higher frequencies, but was not absolutely stable: although the CPU could pass some tests, including S&M, we had problems with other applications. So, 2.5GHz frequency should be considered the highest peak we achieved.

For the memory to be stable we had chosen 1:10 divisor in the BIOS Setup, which corresponded to the DDR333 option. Thus, the memory was working at 250MHz when the Sempron 2600+ was overclocked to 2.5GHz.

We want to emphasize the fact that the temperature of the Sempron 2600+ remained rather low even at overclocking with an increased core voltage. The maximum temperature we observed when running the CPU-burning S&M utility was 48-49°C.

So, we managed to increase the frequency of our Sempron 2600+ by more than 50% at overclocking, which is a very satisfying result. At least many processors that permitted such a high frequency gain used to be “an overclocker’s choice” of various times.