But isn't one. However if you are really interested in doing some major number crunching Dual Processor M'Boards are the way to go.
Now we come to the hard part generally Servers have no Video, Keyboard or Mouse and even if they have the ability to have these things they are all low end particuarly the Video which is on-board with no AGP or Express PCI Slots. They are built for number crunching and sending data across a network of some description at great speed not to be used as a workstation.
But Tyan has one Dual Processor M'Board that may fit your needs you can find it at
http://www.tyan.com/products/html/tigeri7505.html
But it uses Xeon CPU's and can come with an on board SCSI Dual Channel Controller I'd go for the one with the SCSI as it gives you far more options to grow.
There are no P4 Dual Processor M'Boards at all!
They also make a Dual AMD M'Board but I wouldn't recommend one unless you do not have to worry about down time and crashes as the ones that I've used have not been anywhere near as stable as the Intel Chipset M'Boards. But they are a lot cheaper not only to buy but to setup as well. They do not require the expensive RAM or anything else But and it is a big BUT they all have on board Video so they are that much slower than a M'Board that can take a daughter card with a GPU on it as the Graphics Processing is done by the CPU/s so they are working much harder to do the same job.
But if you use either of these M'Boards you'll need a really good case and Antec make a very nice unit that they call a server case but it comes without a Power Supply as you are expected to buy a PS that suits your needs. Again I would recommend an Antec PS to suit your M'Board and number of HDD's that you expect to install and go for the biggest that you can afford as you'll eventually use it to its capacity and with the ability to cram in 30 SCSI devices you'll need a lot of power not to mention all the fans that can be cliped into the case to keep things really cool. The case can be found at
http://www.antec.com/us/productDetails.php?ProdID=81003
And PS's at
http://www.antec.com/us/productDetails.php?ProdID=20480
That is the 480 W which is the absolute smallest I would recommend but depending on the M'Board it may not be the right one as it only has a 20 pin AT connector. Some of those M'Boards use a 24 pin AT connector so you would have to look at the 500 W or bigger.
These things ain't cheap and if you find a maker who is selling complete units cheap they will be the basic M'Boards which have on board Video and be slow in comparison to what you could have for only a few more $.
The Xeon's behave much like the P4's except they have more L2 Cache on them so they appear faster and with a full SCSI HDD package they will just blow the socks off what is sold as even a high end workstation and better still last you for many more years than any normal P4 ever could.
Right at this point in time I have an old Gigabyte GA6 BXDU M'Board with 2 1 GIG P3/s 1 GIG of SDRAM and it still works faster than the latest 3.2 GIG P4 that I should be using.
It's limited to only a 64 MEG AGP Video card and 2 X at that but it just works which isn't bad for something that was originally sold as a Dual P2 Slot 1 M'Board but it is limited in what it can run as it can only handle 100 MHZ FSB CPU's and 256 MEG RAM Sticks.
But with 30 SCSI devices available it is still faster than a P4 with SATA drives although admittedly it also cost a lot more as well at the time and even today would be far more expensive than a new single CPU system.
I almost forgot if you want to go with a Dual Processor System forget about XP Home and only consider XP Pro the second CPU will not be seen with the Home version so you will be wasting your money in buying it and the hardware that goes with it.
I hope that helps you and doesn't confuse you to much.
Col :)