I'm hoping you know about the chipset change that is surely a significant hardware change that separates the v1 from the v2 motherboards in the Z400/Z600/Z600 series. That opened up use not only of new processors but also opened use of registered ECC in addition to unregistered ECC memory. And it allowed the Z400 to access more physical memory.
As for the Z420/Z620/Z820 series...... expecting HP to unsolder, reprogram, and resolder in chips on the older v1 motherboards to perhaps be stable to HP standards is a reach. I have posted here about how easy it is to buy a v2 motherboard off eBay and swap out the old v1 motherboard. That is an afternoon project. I've done it.
HP could have shut down our posting here about all the secrets of how to upgrade processors in various HP workstations years ago, and they have not. We even can receive help from talented and knowledgeable HP engineers here. So, gripe all you wish, but I've felt for years now that HP actually encourages creative recycling of their excellent workstations through this forum. There are a lot of college students and high school students who have gained access to used HP workstations and then upgraded to faster used processors and gotten good used memory via eBay or other sources. This is the one practical source on the internet for such targeted guidance.
