The Pentium D's are dual-core and are made on the 90nm process, they also feature 1MB L2 cache. The Thermal Design Power is rated at 90W for the 820, and 130W for the 830 and 840.
The platform uses the new 945 chipset which supports a 1066MHz FSB and 4GB of DDR2 667MHz memory. It further supports Serial ATA300, Intel SpeedStep, PCI Express x16, Gigabit Ethernet and Intel High Definition Audio which supports up to 7.1 surround sound. Another feature is Intel Matrix Storage Technology which adds support for RAID 5 and 10 levels.
There are two different versions of the 945 chipset, you have the 945G with the integrated Intel GMA 950 graphics solution and the 945P without integrated graphics.
Intel's 945G chipset
The Intel GMA 950 supports 1080i and offers support for an optional Media Expansion Card to watch TV on your home PC. A review of the 945 chipset can be found at Bytesector.
The 945 chipset is comparable to the 955X chipset but lacks some features of its big brother. It only supports 4GB of memory, the 955X supports 8GB, and also lacks ECC and some optimization techniques. Another major difference between both chipsets is that the 945 doesn't support dual-core processors with Hyper-Threading, like the Intel Pentium 4 Extreme Edition 840.
The Intel Pentium D 820, 830 and 840 respectively cost $241, $316 and $530 in 1,000 unit quantities and the Intel 945G and 945P Express Chipsets are priced at US$42 and US$38 respectively, in 1,000-unit quantities.