Quad-core PCs are starting to appear as prices come down and vendors seek to differentiate their new PCs from previous dual-core systems, according to C|Net on Tuesday. That differentiation also extends to Apple.

These quad-core processors use a 45 nanometer fabrication process and pack many more transistors than their dual-core predecessors.

For example, the new Hewlett-Packard s3430f desktop has an AMD low power quad-core processor, includes 4 GB of RAM, a 500 GB SATA hard disk and an Nvidia GeForce 8500 GT GPU, all for US$999.

While some of the kinks are still being worked out with Intelis Quad Q9xxx series, they too are on their way into PC desktops.

Hewlett-Packard s3430f w/quad-core

Of course, a quad-core processor, just like the dual-core CPUs, requires an OS that can handle multiple threads, via Symmetric MultiProcessing (SMP). Vista, the Linux 2.6 kernel, and Mac OS X since the beginning can do that, and desktop users who are heavy into multiple computing and/or video tasks can readily utilize the power of such a CPU. In addition, 4 GB of RAM is appearing as the consensus memory requirement for such quad-core systems.

So far, Apple has chosen to differentiate its consumer line, the iMac, from the professional line, via the number of cores and has stuck with two cores in the iMac. While the Intel Core 2 Duo/Penryn is a strong, 64-bit processor, power hungry PC users tend to fill in Appleis product line gap with high-powered desktop Windows game machines and Linux systems for computation and visualization.

Appleis only quad-core computer currently for sale, the low end Mac Pro, sells for a hefty US$2,299 and comes with only 2 GB of RAM standard. It weighs a whopping 42.4 pounds. While it has some serious professional-level features that donit make it into the newspaper-ad-oriented H-P $999 PCs, it still reflects a gap in Appleis product line that Hewlett-Packard seems to be getting better and better at exploiting lately. For example, the subcompact Mini-Note notebook announced earlier this month.

No doubt, when Apple and Intel have a low cost, iMac motherboard design that supports quad-core flawlessly for both Mac OS X and Windows in Boot Camp, weill see the arrival of quad cores in that product line as well. Meanwhile, Hewlett-Packard isnit just sitting around.