|In case you are still out there looking for an x64 socket 478 CPU then you need to locate an Intel 511 you must be careful as there are a couple of 511chips. |
the link below is to Intel's website to the correct chip.
The SLcodes are, SL8JX, SL88G, SL7PK, SL7E2, SL7K9, SL7D8
These SLcodes are only socket 478
this 511 is a P4 1M cache, 2.8AGHZ 533 FSB. (if it is not the "A" it is not the right one) As far as I've been able to find this is the only option. I have not found any with a faster FSB or higher clock speed. I spoke to Intel and have verified that this chip regardless of the socket it is x64.
The biggest issue that I can see with this chip is that due to the age of the motherboard that support 478 BIOS support for a x64 chip may be skeetchy