Energy efficient PC's - part three

As mentioned in the previous post, we cannot directly compare video card solutions, but we can assume integrated/onboard video uses less power than video cards.

The GeForce 7600 GS seem to be particularly energy efficient video card (also the GeForce 7600 GT if you need more performance).

CPU: For someone that wants good performance and low energy, the Intel Core 2 Duo CPU is a reasonably energy efficient option. The Core 2 Duos with lower clock speeds are sure to consume less energy. The AMD alternative is the AMD Athlon 64 X2 Dual-Core 3800+. It is the bottom end CPU of the AMD X2 series and has about 7/8th the performance of the comparative Intel Core 2 Duo E6300. It only uses 5/8th the power. AMD chips are also much cheaper than the Intel CPU's. On the AMD option I would advise using the AMD Athlon 64 X2 Dual-Core 3800+ Windsor (a remarkable low 35 Watts) - The AMD code is ADD3800CUBOX

My impression is that Intel and AMD have taken different approaches to dual core architectures. The Intel cores are more tightly bound to specific tasks. The AMD cores are more general purpose. The Intel dual core is closer to one unit, and the AMD core is more towards parallel processors.

When buying RAM, you should go for low voltage RAM. DDR2 runs at 1.8Volts and DDR runs at 2.5Volts (Ive seen a 1.5Volt DDR2 solution). You should buy your DDR2 RAM in pairs - it helps a bit with the throughput. Also try to ensure your RAM and CPU is balanced. It is no use having very high frequency RAM when the interface between the RAM and the CPU cannot handle the speeds that the DDR2 RAM chip can spew it out. If you run at an unnecessary high frequency, you will just waste energy. The CPU also has a RAM Cache, which also reduces the need for fast RAM. For example, the Intel Core 2 Duo E6300 has a front side bus (FSB) speed of 1066MHz. So it has little use to have a pair of DDR2 RAM chips running over 533MHz. You could do better to look at latency (response time). In general, RAM chips with low "CAS" scores have good response times.

The way AMD works with RAM is different. I gather the two AMD CPU's interface more directly with the RAM. The speed of the CPU interface with RAM is dependent on the CPU clock speed. The clock speed of the "3800+" is 2000MHZ, so a good RAM speed would be 2000/n, where n is an integer. So a good memory speed would be 667MHz (from 2000MHz/3). AMD CPU's get good performance boosts from low latency (low CAS) as the AMD CPUS are connected a bit more intimately with the RAM.

Your motherboard and chipset will be based on the AMD or Intel CPU. You need to make sure your BIOS have power management features such as ACPI S3 or S4. I would advise avoiding the nforce chipsets on you motherboard as they tend to consume morew power. The chipset normally relates to the "northbridge" or the glue between the CPU and components that interact a lot with the CPU (for example your video card). The nforce4 chip runs particularly hot. Nvidia tried to do too much with the nforce4 - they combined the "northbride" and "southbridge" in the nforce4.

Hard disk. From what I read, the Western Digital Caviar seem to be consistently efficient.

Importantly, you need an efficient power supply. The power supply converts AC to DC, and if it converts too much power, some of it will go too waste. So you need a power supply that responds to the changes in PC power demand. You need a power supply with Active Power Factor Correction (PFC), that also do it efficiently (If you buy a PC without asking, it will have a passive power supply) The "Cooler Master iGreen" power supply is an example of an efficient power supply.

So for the best power efficiency, low cost and good performance, get the AMD 3800+ Windsor. If you need more performance, go the Intel route. This is April 2007, and the Energy Efficiency landscape will probably change in the next few months.