Intel Pentium D processor model 820 may not be compatible with at least some of the chipsets by third party designers, according to ASUS, NVIDIA and X-bit labs performance testing experience. The lowest-speed grade dual-core processor from Intel does not work properly on some of NVIDIA nForce4 Intel Edition-based mainboards, it emerged.

“Yes, ASUS P5ND2-SLI Deluxe motherboard does [support Pentium D 820 processor], but the Intel Pentium D 820 processor works only in single-core mode due to chipset limitation.,” claimed a statement over ASUSTeK Computer technology support web-site, which has been removed after the weekend.

NVIDIA’s spokesperson confirmed that the company had scrapped support for Intel Pentium D processor 820, which works at 2.80GHz, on its chipsets citing low demand for such chip from enthusiasts. NVIDIA’s nForce4 SLI Intel Edition chipsets will only support Intel dual-core processors at 3.0GHz and above, including Intel Pentium D and Intel Pentium Extreme Edition products.

“We decided not to support the lowest performance 2.80GHz dual-core at this point. We expect very limited demand in the enthusiast and gaming segment for this SKU and we decided not to spend engineering resources qualifying it for now… We support 3.0GHz and above,” said Bryan Del Rizzo.

According to internal testing of Intel Pentium D 820 chip, the product does not run stably enough on NVIDIA reference nForce4 SLI Intel Edition mainboard as well as ASUS P5ND2-SLI Deluxe mainboard. Intel Pentium Extreme Edition 840, which is also Intel dual-core desktop chip that is even more advanced, works fine on the mentioned platforms.

Intel’s first family of dual-core chips for desktops originally code-named Smithfield consists of Intel Pentium D 800-series as well as Intel Pentium Extreme Edition central processing units. Initial Intel Pentium D 800-series central processing units use 800MHz Quad Pumped Bus, integrate 2MB (1MB per core) L2 cache and utilize LGA775 form-factor. The dual-core desktop processors will be made using 90nm process technology, each processing engine will use the same architecture with the current Pentium 4 “Prescott” chip and will sport EM64T, EDB as well as Enhanced Intel SpeedStep technologies. Intel Pentium D processors will not enable Hyper-Threading technology leaving this as a prerogative of Intel Pentium Extreme Edition processor 840.

Some sources reported that Intel’s dual-core Intel Pentium D products will be relatively affordable: $241, $316 or $530 – depending on the speed-bin and model – for 820 (2.80GHz), 830 (3.00GHz) or 840 (3.20GHz) chips respectively. Intel Pentium Extreme Edition processor 840 that also runs at 3.20GHz, but with HT technology enabled, costs $999 in 1000-unit quantities and is available now from PC makers like Dell.

Intel Corp. did not comment on the news-story.